PROC(5)                    Linux Programmer's Manual                   PROC(5)
NAME
       proc - process information pseudo-filesystem

DESCRIPTION
       The  proc filesystem is a pseudo-filesystem which provides an interface
       to kernel data structures.  It is commonly mounted at /proc.   Most  of
       it is read-only, but some files allow kernel variables to be changed.

   Mount options
       The proc filesystem supports the following mount options:

       hidepid=n (since Linux 3.3)
              This   option   controls  who  can  access  the  information  in
              /proc/[pid] directories.  The argument, n, is one of the follow-
              ing values:

              0   Everybody  may  access all /proc/[pid] directories.  This is
                  the traditional behavior, and  the  default  if  this  mount
                  option is not specified.

              1   Users  may  not  access  files and subdirectories inside any
                  /proc/[pid]  directories  but  their  own  (the  /proc/[pid]
                  directories  themselves  remain  visible).   Sensitive files
                  such as /proc/[pid]/cmdline and /proc/[pid]/status  are  now
                  protected  against other users.  This makes it impossible to
                  learn whether any user is running  a  specific  program  (so
                  long  as  the program doesn't otherwise reveal itself by its
                  behavior).

              2   As for mode 1, but in addition the  /proc/[pid]  directories
                  belonging  to other users become invisible.  This means that
                  /proc/[pid] entries can no longer be used  to  discover  the
                  PIDs  on  the  system.   This  doesn't  hide the fact that a
                  process with a specific PID value exists (it can be  learned
                  by  other  means,  for  example,  by "kill -0 $PID"), but it
                  hides a process's UID and  GID,  which  could  otherwise  be
                  learned  by  employing  stat(2)  on a /proc/[pid] directory.
                  This greatly complicates an  attacker's  task  of  gathering
                  information   about  running  processes  (e.g.,  discovering
                  whether some daemon is  running  with  elevated  privileges,
                  whether  another  user  is  running  some sensitive program,
                  whether other users are running any program at all,  and  so
                  on).

       gid=gid (since Linux 3.3)
              Specifies  the  ID  of  a  group whose members are authorized to
              learn  process  information  otherwise  prohibited  by   hidepid
              (ie/e/,  users  in this group behave as though /proc was mounted
              with hidepid=0.  This group should be used instead of approaches
              such as putting nonroot users into the sudoers(5) file.

   Files and directories
       The  following  list  describes many of the files and directories under
       the /proc hierarchy.

       /proc/[pid]
              There is a numerical subdirectory for each running process;  the
              subdirectory is named by the process ID.  Each such subdirectory
              contains the following pseudo-files and directories.

       /proc/[pid]/attr
              The files in this directory provide an API for security modules.
              The  contents  of  this directory are files that can be read and
              written in  order  to  set  security-related  attributes.   This
              directory  was  added  to support SELinux, but the intention was
              that the API be general enough to support  other  security  mod-
              ules.   For  the purpose of explanation, examples of how SELinux
              uses these files are provided below.

              This directory is present only if the kernel was configured with
              CONFIG_SECURITY.

       /proc/[pid]/attr/current (since Linux 2.6.0)
              The  contents  of  this  file  represent  the  current  security
              attributes of the process.

              In SELinux, this file is used to get the security context  of  a
              process.   Prior to Linux 2.6.11, this file could not be used to
              set the security context (a  write  was  always  denied),  since
              SELinux  limited  process security transitions to execve(2) (see
              the description of /proc/[pid]/attr/exec, below).   Since  Linux
              2.6.11,  SELinux  lifted  this  restriction and began supporting
              "set" operations via writes to this node if authorized  by  pol-
              icy,  although use of this operation is only suitable for appli-
              cations that are trusted  to  maintain  any  desired  separation
              between  the  old  and  new  security  contexts.  Prior to Linux
              2.6.28, SELinux did not allow threads  within  a  multi-threaded
              process  to set their security context via this node as it would
              yield an  inconsistency  among  the  security  contexts  of  the
              threads  sharing  the  same  memory  space.  Since Linux 2.6.28,
              SELinux lifted this restriction and began supporting "set" oper-
              ations  for  threads  within  a multithreaded process if the new
              security context is bounded by the old security  context,  where
              the  bounded  relation  is defined in policy and guarantees that
              the new security context has a subset of the permissions of  the
              old security context.  Other security modules may choose to sup-
              port "set" operations via writes to this node.

       /proc/[pid]/attr/exec (since Linux 2.6.0)
              This file represents the attributes to  assign  to  the  process
              upon a subsequent execve(2).

              In  SELinux,  this is needed to support role/domain transitions,
              and execve(2) is the preferred point to  make  such  transitions
              because  it offers better control over the initialization of the
              process in the new security label and the inheritance of  state.
              In SELinux, this attribute is reset on execve(2) so that the new
              program reverts to the default behavior for any execve(2)  calls
              that  it  may  make.  In SELinux, a process can set only its own
              /proc/[pid]/attr/exec attribute.

       /proc/[pid]/attr/fscreate (since Linux 2.6.0)
              This file represents the attributes to assign to  files  created
              by  subsequent  calls  to  open(2),  mkdir(2),  symlink(2),  and
              mknod(2)

              SELinux employs this file to support creation of a  file  (using
              the  aforementioned  system  calls)  in  a secure state, so that
              there is no risk of inappropriate access being obtained  between
              the  time  of creation and the time that attributes are set.  In
              SELinux, this attribute is reset on execve(2), so that  the  new
              program  reverts  to  the default behavior for any file creation
              calls it may make, but the attribute will persist across  multi-
              ple file creation calls within a program unless it is explicitly
              reset.   In  SELinux,  a  process   can   set   only   its   own
              /proc/[pid]/attr/fscreate attribute.

       /proc/[pid]/attr/prev (since Linux 2.6.0)
              This  file  contains  the security context of the process before
              the  last  execve(2);   that   is,   the   previous   value   of
              /proc/[pid]/attr/current.

       /proc/[pid]/attr/keycreate (since Linux 2.6.18)
              If  a process writes a security context into this file, all sub-
              sequently created keys (add_key(2)) will be  labeled  with  this
              context.   For  further  information, see the kernel source file
              Documentation/keys.txt.

       /proc/[pid]/attr/socketcreate (since Linux 2.6.18)
              If a process writes a security context into this file, all  sub-
              sequently created sockets will be labeled with this context.

       /proc/[pid]/auxv (since 2.6.0-test7)
              This  contains  the  contents of the ELF interpreter information
              passed to the process at exec time.  The format is one  unsigned
              long  ID  plus one unsigned long value for each entry.  The last
              entry contains two zeros.  See also getauxval(3).

       /proc/[pid]/cgroup (since Linux 2.6.24)
              This file describes control groups  to  which  the  process/task
              belongs.   For each cgroup hierarchy there is one entry contain-
              ing colon-separated fields of the form:

                  5:cpuacct,cpu,cpuset:/daemons

              The colon-separated fields are, from left to right:

                  1. hierarchy ID number

                  2. set of subsystems bound to the hierarchy

                  3. control group in  the  hierarchy  to  which  the  process
                     belongs

              This  file is present only if the CONFIG_CGROUPS kernel configu-
              ration option is enabled.

       /proc/[pid]/clear_refs (since Linux 2.6.22)

              This is a  write-only  file,  writable  only  by  owner  of  the
              process.

              The following values may be written to the file:

              1 (since Linux 2.6.22)
                     Reset  the  PG_Referenced and ACCESSED/YOUNG bits for all
                     the pages associated with the  process.   (Before  kernel
                     2.6.32,  writing  any nonzero value to this file had this
                     effect.)

              2 (since Linux 2.6.32)
                     Reset the PG_Referenced and ACCESSED/YOUNG bits  for  all
                     anonymous pages associated with the process.

              3 (since Linux 2.6.32)
                     Reset  the  PG_Referenced and ACCESSED/YOUNG bits for all
                     file-mapped pages associated with the process.

              Clearing the PG_Referenced and ACCESSED/YOUNG  bits  provides  a
              method  to  measure  approximately  how much memory a process is
              using.  One first inspects the values in the "Referenced" fields
              for  the  VMAs  shown in /proc/[pid]/smaps to get an idea of the
              memory footprint of the process.  One then clears the  PG_Refer-
              enced  and  ACCESSED/YOUNG  bits  and,  after some measured time
              interval, once again inspects the  values  in  the  "Referenced"
              fields  to  get an idea of the change in memory footprint of the
              process during the measured interval.  If one is interested only
              in  inspecting the selected mapping types, then the value 2 or 3
              can be used instead of 1.

              A further value can be written to affect a different bit:

              4 (since Linux 3.11)
                     Clear the soft-dirty bit for  all  the  pages  associated
                     with  the  process.   This  is  used (in conjunction with
                     /proc/[pid]/pagemap) by the check-point restore system to
                     discover which pages of a process have been dirtied since
                     the file /proc/[pid]/clear_refs was written to.

              Writing any value to  /proc/[pid]/clear_refs  other  than  those
              listed above has no effect.

              The  /proc/[pid]/clear_refs  file  is  present  only if the CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/[pid]/cmdline
              This read-only file holds the  complete  command  line  for  the
              process,  unless  the  process is a zombie.  In the latter case,
              there is nothing in this file: that is, a read on this file will
              return  0 characters.  The command-line arguments appear in this
              file as a set of strings separated by null bytes ('\0'), with  a
              further null byte after the last string.

       /proc/[pid]/comm (since Linux 2.6.33)
              This file exposes the process's comm value--that is, the command
              name associated with the process.  Different threads in the same
              process   may   have   different  comm  values,  accessible  via
              /proc/[pid]/task/[tid]/comm.   A  thread  may  modify  its  comm
              value,  or  that of any of other thread in the same thread group
              (see the discussion of CLONE_THREAD in clone(2)), by writing  to
              the   file   /proc/self/task/[tid]/comm.   Strings  longer  than
              TASK_COMM_LEN (16) characters are silently truncated.

              This file provides a superset of the  prctl(2)  PR_SET_NAME  and
              PR_GET_NAME operations, and is employed by pthread_setname_np(3)
              when used to rename threads other than the caller.

       /proc/[pid]/coredump_filter (since Linux 2.6.23)
              See core(5).

       /proc/[pid]/cpuset (since Linux 2.6.12)
              See cpuset(7).

       /proc/[pid]/cwd
              This is a symbolic link to the current working directory of  the
              process.   To  find out the current working directory of process
              20, for instance, you can do this:

                  $ cd /proc/20/cwd; /bin/pwd

              Note that the pwd command is often a shell built-in,  and  might
              not work properly.  In bash(1), you may use pwd -P.

              In  a  multithreaded process, the contents of this symbolic link
              are not available if the  main  thread  has  already  terminated
              (typically by calling pthread_exit(3)).

       /proc/[pid]/environ
              This file contains the environment for the process.  The entries
              are separated by null bytes ('\0'), and there may be a null byte
              at  the  end.   Thus, to print out the environment of process 1,
              you would do:

                  $ strings /proc/1/environ

       /proc/[pid]/exe
              Under Linux 2.2 and later, this file is a symbolic link contain-
              ing  the actual pathname of the executed command.  This symbolic
              link can be dereferenced normally; attempting to  open  it  will
              open  the  executable.  You can even type /proc/[pid]/exe to run
              another copy of the same executable that is being run by process
              [pid].   If  the  pathname  has been unlinked, the symbolic link
              will contain the string '(deleted)'  appended  to  the  original
              pathname.  In a multithreaded process, the contents of this sym-
              bolic link are not available if the main thread has already ter-
              minated (typically by calling pthread_exit(3)).

              Under Linux 2.0 and earlier, /proc/[pid]/exe is a pointer to the
              binary which was executed, and appears as a  symbolic  link.   A
              readlink(2)  call  on this file under Linux 2.0 returns a string
              in the format:

                  [device]:inode

              For example, [0301]:1502 would be inode 1502 on device major  03
              (IDE,  MFM,  etc. drives) minor 01 (first partition on the first
              drive).

              find(1) with the -inum option can be used to locate the file.

       /proc/[pid]/fd/
              This is a subdirectory containing one entry for each file  which
              the process has open, named by its file descriptor, and which is
              a symbolic link to the actual file.  Thus, 0 is standard  input,
              1 standard output, 2 standard error, and so on.

              For  file descriptors for pipes and sockets, the entries will be
              symbolic links whose content is the file type with the inode.  A
              readlink(2) call on this file returns a string in the format:

                  type:[inode]

              For  example, socket:[2248868] will be a socket and its inode is
              2248868.  For sockets, that inode  can  be  used  to  find  more
              information in one of the files under /proc/net/.

              For  file  descriptors  that  have no corresponding inode (e.g.,
              file descriptors produced by epoll_create(2),  eventfd(2),  ino-
              tify_init(2),  signalfd(2), and timerfd(2)), the entry will be a
              symbolic link with contents of the form

                  anon_inode:<file-type>

              In some cases, the file-type is surrounded by square brackets.

              For example, an epoll file descriptor will have a symbolic  link
              whose content is the string anon_inode:[eventpoll].

              In  a  multithreaded process, the contents of this directory are
              not available if the main thread has already  terminated  (typi-
              cally by calling pthread_exit(3)).

              Programs  that  will take a filename as a command-line argument,
              but will not take input from standard input if  no  argument  is
              supplied,  or that write to a file named as a command-line argu-
              ment, but will not send their output to standard  output  if  no
              argument  is  supplied, can nevertheless be made to use standard
              input or standard out using /proc/[pid]/fd.  For example, assum-
              ing  that -i is the flag designating an input file and -o is the
              flag designating an output file:

                  $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...

              and you have a working filter.

              /proc/self/fd/N is approximately the same as /dev/fd/N  in  some
              UNIX and UNIX-like systems.  Most Linux MAKEDEV scripts symboli-
              cally link /dev/fd to /proc/self/fd, in fact.

              Most systems provide symbolic links /dev/stdin, /dev/stdout, and
              /dev/stderr, which respectively link to the files 0, 1, and 2 in
              /proc/self/fd.  Thus the example command above could be  written
              as:

                  $ foobar -i /dev/stdin -o /dev/stdout ...

       /proc/[pid]/fdinfo/ (since Linux 2.6.22)
              This  is a subdirectory containing one entry for each file which
              the process has open, named by its file descriptor.   The  files
              in this directory are readable only by the owner of the process.
              The contents of each file can  be  read  to  obtain  information
              about the corresponding file descriptor.  The content depends on
              the type of file referred to by the corresponding descriptor.

              For regular files and directories, we see something like:

                  $ cat /proc/12015/fdinfo/4
                  pos:    1000
                  flags:  01002002
                  mnt_id: 21

              The pos field is a decimal number showing the current file  off-
              set.   The flags field is an octal number that displays the file
              access mode and file status flags  (see  open(2)).   The  mnt_id
              field,  present  since  Linux 3.15, is the ID of the mount point
              containing    this    file.     See    the    description     of
              /proc/[pid]/mountinfo.

              For  eventfd  file descriptors (see eventfd(2)), we see the fol-
              lowing fields:

                  pos: 0
                  flags:    02
                  mnt_id:   10
                  eventfd-count:               40

              eventfd-count is the current value of the  eventfd  counter,  in
              hexadecimal.

              For  epoll file descriptors (see epoll(7)), we see the following
              fields:

                  pos: 0
                  flags:    02
                  mnt_id:   10
                  tfd:        9 events:       19 data: 74253d2500000009
                  tfd:        7 events:       19 data: 74253d2500000007

              Each of the lines  beginning  tfd  describes  one  of  the  file
              descriptors  being  monitored via the epoll file descriptor (see
              epoll_ctl(2) for some details).  The tfd field is the number  of
              the  file descriptor.  The events field is a hexadecimal mask of
              the events being monitored for this file descriptor.   The  data
              field is the data value associated with this file descriptor.

              For signalfd file descriptors (see signalfd(2)), we see the fol-
              lowing fields:

                  pos: 0
                  flags:    02
                  mnt_id:   10
                  sigmask:  0000000000000006

              sigmask is the hexadecimal mask of signals that are accepted via
              this  signalfd  file descriptor.  (In this example, bits 2 and 3
              are set, corresponding to the signals SIGINT  and  SIGQUIT;  see
              signal(7).)

       /proc/[pid]/io (since kernel 2.6.20)
              This file contains I/O statistics for the process, for example:

                  # cat /proc/3828/io
                  rchar: 323934931
                  wchar: 323929600
                  syscr: 632687
                  syscw: 632675
                  read_bytes: 0
                  write_bytes: 323932160
                  cancelled_write_bytes: 0

              The fields are as follows:

              rchar: characters read
                     The number of bytes which this task has caused to be read
                     from storage.  This is simply the sum of bytes which this
                     process  passed  to read(2) and similar system calls.  It
                     includes things such as terminal I/O and is unaffected by
                     whether or not actual physical disk I/O was required (the
                     read might have been satisfied from pagecache).

              wchar: characters written
                     The number of bytes which this task has caused, or  shall
                     cause  to be written to disk.  Similar caveats apply here
                     as with rchar.

              syscr: read syscalls
                     Attempt to count the number of read I/O  operations--that
                     is, system calls such as read(2) and pread(2).

              syscw: write syscalls
                     Attempt to count the number of write I/O operations--that
                     is, system calls such as write(2) and pwrite(2).

              read_bytes: bytes read
                     Attempt to count the number of bytes which  this  process
                     really  did  cause  to be fetched from the storage layer.
                     This is accurate for block-backed filesystems.

              write_bytes: bytes written
                     Attempt to count the number of bytes which  this  process
                     caused to be sent to the storage layer.

              cancelled_write_bytes:
                     The big inaccuracy here is truncate.  If a process writes
                     1MB to a file and then deletes the file, it will in  fact
                     perform  no writeout.  But it will have been accounted as
                     having caused 1MB of write.  In other words:  this  field
                     represents  the number of bytes which this process caused
                     to not happen, by truncating pagecache.  A task can cause
                     "negative"  I/O  too.   If this task truncates some dirty
                     pagecache, some I/O which another task has been accounted
                     for (in its write_bytes) will not be happening.

              Note:  In  the  current implementation, things are a bit racy on
              32-bit systems: if process A reads  process  B's  /proc/[pid]/io
              while  process  B  is  updating  one  of  these 64-bit counters,
              process A could see an intermediate result.

       /proc/[pid]/gid_map (since Linux 3.5)
              See user_namespaces(7).

       /proc/[pid]/limits (since Linux 2.6.24)
              This file displays the soft limit, hard limit, and units of mea-
              surement  for  each  of the process's resource limits (see getr-
              limit(2)).  Up to and including Linux 2.6.35, this file is  pro-
              tected  to  allow  reading  only by the real UID of the process.
              Since Linux 2.6.36, this file is readable by all  users  on  the
              system.

       /proc/[pid]/map_files/ (since kernel 3.3)
              This  subdirectory  contains  entries  corresponding  to memory-
              mapped files (see mmap(2)).  Entries are named by memory  region
              start  and  end address pair (expressed as hexadecimal numbers),
              and are symbolic links to the mapped files themselves.  Here  is
              an example, with the output wrapped and reformatted to fit on an
              80-column display:

                  # ls -l /proc/self/map_files/
                  lr--------. 1 root root 64 Apr 16 21:31
                              3252e00000-3252e20000 -> /usr/lib64/ld-2.15.so
                  ...

              Although these entries are present for memory regions that  were
              mapped  with  the MAP_FILE flag, the way anonymous shared memory
              (regions created with the MAP_ANON | MAP_SHARED flags) is imple-
              mented  in  Linux  means  that  such regions also appear on this
              directory.  Here is an example where  the  target  file  is  the
              deleted /dev/zero one:

                  lrw-------. 1 root root 64 Apr 16 21:33
                              7fc075d2f000-7fc075e6f000 -> /dev/zero (deleted)

              This  directory  appears  only  if the CONFIG_CHECKPOINT_RESTORE
              kernel   configuration    option    is    enabled.     Privilege
              (CAP_SYS_ADMIN)  is required to view the contents of this direc-
              tory.

       /proc/[pid]/maps
              A file containing the currently mapped memory regions and  their
              access  permissions.   See  mmap(2) for some further information
              about memory mappings.

              The format of the file is:

       address           perms offset  dev   inode       pathname
       00400000-00452000 r-xp 00000000 08:02 173521      /usr/bin/dbus-daemon
       00651000-00652000 r--p 00051000 08:02 173521      /usr/bin/dbus-daemon
       00652000-00655000 rw-p 00052000 08:02 173521      /usr/bin/dbus-daemon
       00e03000-00e24000 rw-p 00000000 00:00 0           [heap]
       00e24000-011f7000 rw-p 00000000 00:00 0           [heap]
       ...
       35b1800000-35b1820000 r-xp 00000000 08:02 135522  /usr/lib64/ld-2.15.so
       35b1a1f000-35b1a20000 r--p 0001f000 08:02 135522  /usr/lib64/ld-2.15.so
       35b1a20000-35b1a21000 rw-p 00020000 08:02 135522  /usr/lib64/ld-2.15.so
       35b1a21000-35b1a22000 rw-p 00000000 00:00 0
       35b1c00000-35b1dac000 r-xp 00000000 08:02 135870  /usr/lib64/libc-2.15.so
       35b1dac000-35b1fac000 ---p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so
       35b1fac000-35b1fb0000 r--p 001ac000 08:02 135870  /usr/lib64/libc-2.15.so
       35b1fb0000-35b1fb2000 rw-p 001b0000 08:02 135870  /usr/lib64/libc-2.15.so
       ...
       f2c6ff8c000-7f2c7078c000 rw-p 00000000 00:00 0    [stack:986]
       ...
       7fffb2c0d000-7fffb2c2e000 rw-p 00000000 00:00 0   [stack]
       7fffb2d48000-7fffb2d49000 r-xp 00000000 00:00 0   [vdso]

              The address field is the address space in the process  that  the
              mapping occupies.  The perms field is a set of permissions:

                   r = read
                   w = write
                   x = execute
                   s = shared
                   p = private (copy on write)

              The  offset  field  is the offset into the file/whatever; dev is
              the device (major:minor); inode is the inode on that device.   0
              indicates that no inode is associated with the memory region, as
              would be the case with BSS (uninitialized data).

              The pathname field will usually be the file that is backing  the
              mapping.  For ELF files, you can easily coordinate with the off-
              set field by looking at the Offset  field  in  the  ELF  program
              headers (readelf -l).

              There are additional helpful pseudo-paths:

                   [stack]
                          The  initial  process's  (also  known  as  the  main
                          thread's) stack.

                   [stack:<tid>] (since Linux 3.4)
                          A thread's stack (where the <tid> is a  thread  ID).
                          It corresponds to the /proc/[pid]/task/[tid]/ path.

                   [vdso] The virtual dynamically linked shared object.

                   [heap] The process's heap.

              If  the pathname field is blank, this is an anonymous mapping as
              obtained via the mmap(2) function.  There  is  no  easy  way  to
              coordinate  this back to a process's source, short of running it
              through gdb(1), strace(1), or similar.

              Under Linux 2.0, there is no field giving pathname.

       /proc/[pid]/mem
              This file can be used to access the pages of a process's  memory
              through open(2), read(2), and lseek(2).

       /proc/[pid]/mountinfo (since Linux 2.6.26)
              This  file contains information about mount points.  It contains
              lines of the form:

              36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
              (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)

              The numbers in  parentheses  are  labels  for  the  descriptions
              below:

              (1)  mount  ID:  unique  identifier  of the mount (may be reused
                   after umount(2)).

              (2)  parent ID: ID of parent mount (or of self for  the  top  of
                   the mount tree).

              (3)  major:minor:  value  of st_dev for files on filesystem (see
                   stat(2)).

              (4)  root: root of the mount within the filesystem.

              (5)  mount point: mount point relative to the process's root.

              (6)  mount options: per-mount options.

              (7)  optional  fields:  zero  or  more  fields   of   the   form
                   "tag[:value]".

              (8)  separator: marks the end of the optional fields.

              (9)  filesystem type: name of filesystem in the form "type[.sub-
                   type]".

              (10) mount source: filesystem-specific information or "none".

              (11) super options: per-superblock options.

              Parsers should ignore all unrecognized  optional  fields.   Cur-
              rently the possible optional fields are:

                   shared:X          mount is shared in peer group X

                   master:X          mount is slave to peer group X

                   propagate_from:X  mount  is  slave and receives propagation
                                     from peer group X (*)

                   unbindable        mount is unbindable

              (*) X is the closest dominant peer  group  under  the  process's
              root.  If X is the immediate master of the mount, or if there is
              no dominant peer group under the same root, then only the  "mas-
              ter:X" field is present and not the "propagate_from:X" field.

              For  more  information  on  mount  propagation  see:  Documenta-
              tion/filesystems/sharedsubtree.txt in the  Linux  kernel  source
              tree.

       /proc/[pid]/mounts (since Linux 2.4.19)
              This  is  a list of all the filesystems currently mounted in the
              process's mount namespace.  The format of  this  file  is  docu-
              mented  in  fstab(5).  Since kernel version 2.6.15, this file is
              pollable: after opening the file for reading, a change  in  this
              file  (i.e.,  a filesystem mount or unmount) causes select(2) to
              mark  the  file  descriptor  as  readable,   and   poll(2)   and
              epoll_wait(2)  mark  the file as having an error condition.  See
              namespaces(7) for more information.

       /proc/[pid]/mountstats (since Linux 2.6.17)
              This file exports information (statistics, configuration  infor-
              mation) about the mount points in the process's mount namespace.
              Lines in this file have the form:

              device /dev/sda7 mounted on /home with fstype ext3 [statistics]
              (       1      )            ( 2 )             (3 ) (4)

              The fields in each line are:

              (1)  The name of the mounted device (or "nodevice" if  there  is
                   no corresponding device).

              (2)  The mount point within the filesystem tree.

              (3)  The filesystem type.

              (4)  Optional  statistics  and  configuration information.  Cur-
                   rently (as at Linux 2.6.26), only  NFS  filesystems  export
                   information via this field.

              This file is readable only by the owner of the process.

              See namespaces(7) for more information.

       /proc/[pid]/ns/ (since Linux 3.0)
              This  is  a subdirectory containing one entry for each namespace
              that supports being manipulated by setns(2).  For more  informa-
              tion, see namespaces(7).

       /proc/[pid]/numa_maps (since Linux 2.6.14)
              See numa(7).

       /proc/[pid]/oom_adj (since Linux 2.6.11)
              This  file  can be used to adjust the score used to select which
              process should be killed in an  out-of-memory  (OOM)  situation.
              The  kernel  uses  this  value  for a bit-shift operation of the
              process's oom_score value: valid values are in the range -16  to
              +15,  plus  the  special  value  -17, which disables OOM-killing
              altogether for this process.  A  positive  score  increases  the
              likelihood  of  this  process  being killed by the OOM-killer; a
              negative score decreases the likelihood.

              The default value for this file is 0; a new process inherits its
              parent's   oom_adj   setting.   A  process  must  be  privileged
              (CAP_SYS_RESOURCE) to update this file.

              Since Linux 2.6.36, use of this file is deprecated in  favor  of
              /proc/[pid]/oom_score_adj.

       /proc/[pid]/oom_score (since Linux 2.6.11)
              This  file  displays  the current score that the kernel gives to
              this process for the purpose of selecting a process for the OOM-
              killer.  A higher score means that the process is more likely to
              be selected by the OOM-killer.  The basis for this score is  the
              amount  of  memory  used  by  the process, with increases (+) or
              decreases (-) for factors including:

              * whether the process creates a lot of  children  using  fork(2)
                (+);

              * whether  the process has been running a long time, or has used
                a lot of CPU time (-);

              * whether the process has a low nice value (i.e., > 0) (+);

              * whether the process is privileged (-); and

              * whether the process is making direct hardware access (-).

              The oom_score also reflects  the  adjustment  specified  by  the
              oom_score_adj or oom_adj setting for the process.

       /proc/[pid]/oom_score_adj (since Linux 2.6.36)
              This  file  can  be used to adjust the badness heuristic used to
              select which process gets killed in out-of-memory conditions.

              The badness heuristic assigns a value  to  each  candidate  task
              ranging  from  0 (never kill) to 1000 (always kill) to determine
              which process is targeted.  The units are roughly  a  proportion
              along  that  range  of  allowed  memory the process may allocate
              from, based on an estimation of its current memory and swap use.
              For  example, if a task is using all allowed memory, its badness
              score will be 1000.  If it is using half of its allowed  memory,
              its score will be 500.

              There  is  an  additional  factor included in the badness score:
              root processes are given 3% extra memory over other tasks.

              The amount of "allowed" memory depends on the context  in  which
              the  OOM-killer was called.  If it is due to the memory assigned
              to the allocating task's cpuset  being  exhausted,  the  allowed
              memory  represents  the set of mems assigned to that cpuset (see
              cpuset(7)).  If  it  is  due  to  a  mempolicy's  node(s)  being
              exhausted,  the  allowed  memory represents the set of mempolicy
              nodes.  If it is due to a memory limit  (or  swap  limit)  being
              reached,  the allowed memory is that configured limit.  Finally,
              if it is due to the entire  system  being  out  of  memory,  the
              allowed memory represents all allocatable resources.

              The  value of oom_score_adj is added to the badness score before
              it is used to determine which task to kill.   Acceptable  values
              range     from     -1000     (OOM_SCORE_ADJ_MIN)     to    +1000
              (OOM_SCORE_ADJ_MAX).  This allows  user  space  to  control  the
              preference  for  OOM-killing,  ranging  from always preferring a
              certain task or completely disabling it from OOM  killing.   The
              lowest  possible  value,  -1000, is equivalent to disabling OOM-
              killing entirely for that task, since it will  always  report  a
              badness score of 0.

              Consequently,  it  is  very  simple for user space to define the
              amount  of  memory  to  consider  for  each  task.   Setting   a
              oom_score_adj  value of +500, for example, is roughly equivalent
              to allowing the remainder of  tasks  sharing  the  same  system,
              cpuset,  mempolicy,  or  memory  controller  resources to use at
              least 50% more memory.  A value of  -500,  on  the  other  hand,
              would  be  roughly  equivalent  to discounting 50% of the task's
              allowed memory from being  considered  as  scoring  against  the
              task.

              For    backward    compatibility    with    previous    kernels,
              /proc/[pid]/oom_adj can still be used to tune the badness score.
              Its value is scaled linearly with oom_score_adj.

              Writing to /proc/[pid]/oom_score_adj or /proc/[pid]/oom_adj will
              change the other with its scaled value.

       /proc/[pid]/pagemap (since Linux 2.6.25)
              This file shows the mapping of each  of  the  process's  virtual
              pages  into  physical page frames or swap area.  It contains one
              64-bit value for each virtual page, with the bits  set  as  fol-
              lows:

                   63     If set, the page is present in RAM.

                   62     If set, the page is in swap space

                   61 (since Linux 3.5)
                          The page is a file-mapped page or a shared anonymous
                          page.

                   60-56 (since Linux 3.11)
                          Zero

                   55 (Since Linux 3.11)
                          PTE is soft-dirty (see the kernel source file  Docu-
                          mentation/vm/soft-dirty.txt).

                   54-0   If  the  page is present in RAM (bit 63), then these
                          bits provide the page frame  number,  which  can  be
                          used to index /proc/kpageflags and /proc/kpagecount.
                          If the page is present in swap (bit 62),  then  bits
                          4-0  give  the  swap  type, and bits 54-5 encode the
                          swap offset.

              Before Linux 3.11, bits 60-55 were used to encode the base-2 log
              of the page size.

              To  employ /proc/[pid]/pagemap efficiently, use /proc/[pid]/maps
              to determine which areas of memory are actually mapped and  seek
              to skip over unmapped regions.

              The  /proc/[pid]/pagemap  file  is  present  only  if  the  CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/[pid]/personality (since Linux 2.6.28)
              This read-only file exposes the process's execution  domain,  as
              set  by  personality(2).   The value is displayed in hexadecimal
              notation.

       /proc/[pid]/root
              UNIX and Linux support the idea of a  per-process  root  of  the
              filesystem,  set  by  the chroot(2) system call.  This file is a
              symbolic link that points to the process's root  directory,  and
              behaves in the same way as exe, and fd/*.

              In  a  multithreaded process, the contents of this symbolic link
              are not available if the  main  thread  has  already  terminated
              (typically by calling pthread_exit(3)).

       /proc/[pid]/seccomp (from Linux 2.6.12 to 2.6.22)
              Read/set  the  seccomp  mode for the process.  If this file con-
              tains the value zero, seccomp mode is not enabled.  Writing  the
              value  1  to this file (irreversibly) places the process in sec-
              comp  mode:  the  only  permitted  system  calls  are   read(2),
              write(2),  _exit(2),  and  sigreturn(2).  This file went away in
              Linux 2.6.23, when it was replaced by  a  prctl(2)-based  mecha-
              nism.

       /proc/[pid]/setgroups (since Linux 3.19)
              See user_namespaces(7).

       /proc/[pid]/smaps (since Linux 2.6.14)
              This  file  shows  memory  consumption for each of the process's
              mappings.  (The pmap(1) command displays similar information, in
              a  form that may be easier for parsing.)  For each mapping there
              is a series of lines such as the following:

                  00400000-0048a000 r-xp 00000000 fd:03 960637       /bin/bash
                  Size:                552 kB
                  Rss:                 460 kB
                  Pss:                 100 kB
                  Shared_Clean:        452 kB
                  Shared_Dirty:          0 kB
                  Private_Clean:         8 kB
                  Private_Dirty:         0 kB
                  Referenced:          460 kB
                  Anonymous:             0 kB
                  AnonHugePages:         0 kB
                  Swap:                  0 kB
                  KernelPageSize:        4 kB
                  MMUPageSize:           4 kB
                  Locked:                0 kB

              The first of these lines shows the same information as  is  dis-
              played for the mapping in /proc/[pid]/maps.  The remaining lines
              show the size of the mapping, the amount of the mapping that  is
              currently  resident  in  RAM  ("Rss"), the process' proportional
              share of this mapping ("Pss"), the number  of  clean  and  dirty
              shared  pages  in the mapping, and the number of clean and dirty
              private pages in the mapping.  "Referenced" indicates the amount
              of  memory  currently marked as referenced or accessed.  "Anony-
              mous" shows the amount of memory that does  not  belong  to  any
              file.   "Swap"  shows how much would-be-anonymous memory is also
              used, but out on swap.

              The "KernelPageSize" entry is the page size used by  the  kernel
              to  back  a  VMA.   This matches the size used by the MMU in the
              majority of cases.  However, one counter-example occurs on PPC64
              kernels whereby a kernel using 64K as a base page size may still
              use 4K pages for the MMU on older processors.   To  distinguish,
              this  patch  reports  "MMUPageSize" as the page size used by the
              MMU.

              The "Locked" indicates whether the mapping is locked  in  memory
              or not.

              "VmFlags"  field represents the kernel flags associated with the
              particular virtual memory area in  two  letter  encoded  manner.
              The codes are the following:

                  rd  - readable
                  wr  - writable
                  ex  - executable
                  sh  - shared
                  mr  - may read
                  mw  - may write
                  me  - may execute
                  ms  - may share
                  gd  - stack segment grows down
                  pf  - pure PFN range
                  dw  - disabled write to the mapped file
                  lo  - pages are locked in memory
                  io  - memory mapped I/O area
                  sr  - sequential read advise provided
                  rr  - random read advise provided
                  dc  - do not copy area on fork
                  de  - do not expand area on remapping
                  ac  - area is accountable
                  nr  - swap space is not reserved for the area
                  ht  - area uses huge tlb pages
                  nl  - non-linear mapping
                  ar  - architecture specific flag
                  dd  - do not include area into core dump
                  sd  - soft-dirty flag
                  mm  - mixed map area
                  hg  - huge page advise flag
                  nh  - no-huge page advise flag
                  mg  - mergeable advise flag

              The   /proc/[pid]/smaps   file  is  present  only  if  the  CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/[pid]/stack (since Linux 2.6.29)
              This file provides a symbolic trace of  the  function  calls  in
              this  process's kernel stack.  This file is provided only if the
              kernel  was  built  with  the  CONFIG_STACKTRACE   configuration
              option.

       /proc/[pid]/stat
              Status  information  about  the process.  This is used by ps(1).
              It is defined in the kernel source file fs/proc/array.c.

              The fields, in order, with their proper scanf(3)  format  speci-
              fiers, are:

              (1) pid  %d
                        The process ID.

              (2) comm  %s
                        The  filename of the executable, in parentheses.  This
                        is visible whether or not the  executable  is  swapped
                        out.

              (3) state  %c
                        One  of  the  following characters, indicating process
                        state:

                        R  Running

                        S  Sleeping in an interruptible wait

                        D  Waiting in uninterruptible disk sleep

                        Z  Zombie

                        T  Stopped (on a  signal)  or  (before  Linux  2.6.33)
                           trace stopped

                        t  Tracing stop (Linux 2.6.33 onward)

                        W  Paging (only before Linux 2.6.0)

                        X  Dead (from Linux 2.6.0 onward)

                        x  Dead (Linux 2.6.33 to 3.13 only)

                        K  Wakekill (Linux 2.6.33 to 3.13 only)

                        W  Waking (Linux 2.6.33 to 3.13 only)

                        P  Parked (Linux 3.9 to 3.13 only)

              (4) ppid  %d
                        The PID of the parent of this process.

              (5) pgrp  %d
                        The process group ID of the process.

              (6) session  %d
                        The session ID of the process.

              (7) tty_nr  %d
                        The  controlling  terminal of the process.  (The minor
                        device number is contained in the combination of  bits
                        31  to  20  and  7 to 0; the major device number is in
                        bits 15 to 8.)

              (8) tpgid  %d
                        The ID of the foreground process group of the control-
                        ling terminal of the process.

              (9) flags  %u
                        The  kernel  flags word of the process.  For bit mean-
                        ings, see the PF_* defines in the Linux kernel  source
                        file  include/linux/sched.h.   Details  depend  on the
                        kernel version.

                        The format for this field was %lu before Linux 2.6.

              (10) minflt  %lu
                        The number of minor faults the process has made  which
                        have not required loading a memory page from disk.

              (11) cminflt  %lu
                        The  number of minor faults that the process's waited-
                        for children have made.

              (12) majflt  %lu
                        The number of major faults the process has made  which
                        have required loading a memory page from disk.

              (13) cmajflt  %lu
                        The  number of major faults that the process's waited-
                        for children have made.

              (14) utime  %lu
                        Amount of time that this process has been scheduled in
                        user   mode,   measured  in  clock  ticks  (divide  by
                        sysconf(_SC_CLK_TCK)).   This  includes  guest   time,
                        guest_time  (time  spent  running  a  virtual CPU, see
                        below), so that applications that are not aware of the
                        guest time field do not lose that time from their cal-
                        culations.

              (15) stime  %lu
                        Amount of time that this process has been scheduled in
                        kernel  mode,  measured  in  clock  ticks  (divide  by
                        sysconf(_SC_CLK_TCK)).

              (16) cutime  %ld
                        Amount of time that this process's waited-for children
                        have  been  scheduled  in user mode, measured in clock
                        ticks (divide  by  sysconf(_SC_CLK_TCK)).   (See  also
                        times(2).)   This  includes  guest  time,  cguest_time
                        (time spent running a virtual CPU, see below).

              (17) cstime  %ld
                        Amount of time that this process's waited-for children
                        have  been scheduled in kernel mode, measured in clock
                        ticks (divide by sysconf(_SC_CLK_TCK)).

              (18) priority  %ld
                        (Explanation for Linux 2.6) For  processes  running  a
                        real-time   scheduling   policy   (policy  below;  see
                        sched_setscheduler(2)), this is the negated scheduling
                        priority, minus one; that is, a number in the range -2
                        to -100, corresponding to real-time  priorities  1  to
                        99.   For  processes  running  under  a  non-real-time
                        scheduling policy, this is the raw nice value (setpri-
                        ority(2))  as  represented  in the kernel.  The kernel
                        stores nice values as numbers in the range 0 (high) to
                        39 (low), corresponding to the user-visible nice range
                        of -20 to 19.

                        Before Linux 2.6, this was a scaled value based on the
                        scheduler weighting given to this process.

              (19) nice  %ld
                        The  nice  value  (see setpriority(2)), a value in the
                        range 19 (low priority) to -20 (high priority).

              (20) num_threads  %ld
                        Number of threads in this process (since  Linux  2.6).
                        Before kernel 2.6, this field was hard coded to 0 as a
                        placeholder for an earlier removed field.

              (21) itrealvalue  %ld
                        The time in jiffies before the next SIGALRM is sent to
                        the  process  due  to an interval timer.  Since kernel
                        2.6.17, this field is no  longer  maintained,  and  is
                        hard coded as 0.

              (22) starttime  %llu
                        The  time  the  process started after system boot.  In
                        kernels before Linux 2.6, this value was expressed  in
                        jiffies.   Since  Linux 2.6, the value is expressed in
                        clock ticks (divide by sysconf(_SC_CLK_TCK)).

                        The format for this field was %lu before Linux 2.6.

              (23) vsize  %lu
                        Virtual memory size in bytes.

              (24) rss  %ld
                        Resident Set Size: number of pages the process has  in
                        real  memory.   This  is  just  the  pages which count
                        toward text, data, or  stack  space.   This  does  not
                        include pages which have not been demand-loaded in, or
                        which are swapped out.

              (25) rsslim  %lu
                        Current soft limit in bytes on the rss of the process;
                        see the description of RLIMIT_RSS in getrlimit(2).

              (26) startcode  %lu
                        The address above which program text can run.

              (27) endcode  %lu
                        The address below which program text can run.

              (28) startstack  %lu
                        The address of the start (i.e., bottom) of the stack.

              (29) kstkesp  %lu
                        The  current value of ESP (stack pointer), as found in
                        the kernel stack page for the process.

              (30) kstkeip  %lu
                        The current EIP (instruction pointer).

              (31) signal  %lu
                        The bitmap of pending signals, displayed as a  decimal
                        number.   Obsolete, because it does not provide infor-
                        mation on real-time  signals;  use  /proc/[pid]/status
                        instead.

              (32) blocked  %lu
                        The  bitmap of blocked signals, displayed as a decimal
                        number.  Obsolete, because it does not provide  infor-
                        mation  on  real-time  signals; use /proc/[pid]/status
                        instead.

              (33) sigignore  %lu
                        The bitmap of ignored signals, displayed as a  decimal
                        number.   Obsolete, because it does not provide infor-
                        mation on real-time  signals;  use  /proc/[pid]/status
                        instead.

              (34) sigcatch  %lu
                        The  bitmap  of caught signals, displayed as a decimal
                        number.  Obsolete, because it does not provide  infor-
                        mation  on  real-time  signals; use /proc/[pid]/status
                        instead.

              (35) wchan  %lu
                        This is the "channel" in which the process is waiting.
                        It  is  the  address of a location in the kernel where
                        the process is sleeping.  The  corresponding  symbolic
                        name can be found in /proc/[pid]/wchan.

              (36) nswap  %lu
                        Number of pages swapped (not maintained).

              (37) cnswap  %lu
                        Cumulative nswap for child processes (not maintained).

              (38) exit_signal  %d  (since Linux 2.1.22)
                        Signal to be sent to parent when we die.

              (39) processor  %d  (since Linux 2.2.8)
                        CPU number last executed on.

              (40) rt_priority  %u  (since Linux 2.5.19)
                        Real-time scheduling priority, a number in the range 1
                        to 99 for processes scheduled under a  real-time  pol-
                        icy,   or   0,   for   non-real-time   processes  (see
                        sched_setscheduler(2)).

              (41) policy  %u  (since Linux 2.5.19)
                        Scheduling policy (see sched_setscheduler(2)).  Decode
                        using the SCHED_* constants in linux/sched.h.

                        The format for this field was %lu before Linux 2.6.22.

              (42) delayacct_blkio_ticks  %llu  (since Linux 2.6.18)
                        Aggregated  block  I/O delays, measured in clock ticks
                        (centiseconds).

              (43) guest_time  %lu  (since Linux 2.6.24)
                        Guest time of the process (time spent running  a  vir-
                        tual  CPU  for  a guest operating system), measured in
                        clock ticks (divide by sysconf(_SC_CLK_TCK)).

              (44) cguest_time  %ld  (since Linux 2.6.24)
                        Guest time of  the  process's  children,  measured  in
                        clock ticks (divide by sysconf(_SC_CLK_TCK)).

              (45) start_data  %lu  (since Linux 3.3)
                        Address above which program initialized and uninitial-
                        ized (BSS) data are placed.

              (46) end_data  %lu  (since Linux 3.3)
                        Address below which program initialized and uninitial-
                        ized (BSS) data are placed.

              (47) start_brk  %lu  (since Linux 3.3)
                        Address  above which program heap can be expanded with
                        brk(2).

              (48) arg_start  %lu  (since Linux 3.5)
                        Address above  which  program  command-line  arguments
                        (argv) are placed.

              (49) arg_end  %lu  (since Linux 3.5)
                        Address  below  program  command-line arguments (argv)
                        are placed.

              (50) env_start  %lu  (since Linux 3.5)
                        Address above which program environment is placed.

              (51) env_end  %lu  (since Linux 3.5)
                        Address below which program environment is placed.

              (52) exit_code  %d  (since Linux 3.5)
                        The thread's exit status in the form reported by wait-
                        pid(2).

       /proc/[pid]/statm
              Provides information about memory usage, measured in pages.  The
              columns are:

                  size       (1) total program size
                             (same as VmSize in /proc/[pid]/status)
                  resident   (2) resident set size
                             (same as VmRSS in /proc/[pid]/status)
                  share      (3) shared pages (i.e., backed by a file)
                  text       (4) text (code)
                  lib        (5) library (unused in Linux 2.6)
                  data       (6) data + stack
                  dt         (7) dirty pages (unused in Linux 2.6)

       /proc/[pid]/status
              Provides  much  of  the  information  in  /proc/[pid]/stat   and
              /proc/[pid]/statm in a format that's easier for humans to parse.
              Here's an example:

                  $ cat /proc/$$/status
                  Name:   bash
                  State:  S (sleeping)
                  Tgid:   3515
                  Pid:    3515
                  PPid:   3452
                  TracerPid:      0
                  Uid:    1000    1000    1000    1000
                  Gid:    100     100     100     100
                  FDSize: 256
                  Groups: 16 33 100
                  VmPeak:     9136 kB
                  VmSize:     7896 kB
                  VmLck:         0 kB
                  VmPin:         0 kB
                  VmHWM:      7572 kB
                  VmRSS:      6316 kB
                  VmData:     5224 kB
                  VmStk:        88 kB
                  VmExe:       572 kB
                  VmLib:      1708 kB
                  VmPMD:         4 kB
                  VmPTE:        20 kB
                  VmSwap:        0 kB
                  Threads:        1
                  SigQ:   0/3067
                  SigPnd: 0000000000000000
                  ShdPnd: 0000000000000000
                  SigBlk: 0000000000010000
                  SigIgn: 0000000000384004
                  SigCgt: 000000004b813efb
                  CapInh: 0000000000000000
                  CapPrm: 0000000000000000
                  CapEff: 0000000000000000
                  CapBnd: ffffffffffffffff
                  CapAmb:   0000000000000000
                  Seccomp:        0
                  Cpus_allowed:   00000001
                  Cpus_allowed_list:      0
                  Mems_allowed:   1
                  Mems_allowed_list:      0
                  voluntary_ctxt_switches:        150
                  nonvoluntary_ctxt_switches:     545

              The fields are as follows:

              * Name: Command run by this process.

              * State: Current state of the process.  One of "R (running)", "S
                (sleeping)",  "D  (disk  sleep)",  "T  (stopped)", "T (tracing
                stop)", "Z (zombie)", or "X (dead)".

              * Tgid: Thread group ID (i.e., Process ID).

              * Pid: Thread ID (see gettid(2)).

              * PPid: PID of parent process.

              * TracerPid: PID of process tracing this process (0 if not being
                traced).

              * Uid,  Gid:  Real,  effective,  saved  set, and filesystem UIDs
                (GIDs).

              * FDSize: Number of file descriptor slots currently allocated.

              * Groups: Supplementary group list.

              * VmPeak: Peak virtual memory size.

              * VmSize: Virtual memory size.

              * VmLck: Locked memory size (see mlock(3)).

              * VmPin: Pinned memory size (since Linux 3.2).  These are  pages
                that can't be moved because something needs to directly access
                physical memory.

              * VmHWM: Peak resident set size ("high water mark").

              * VmRSS: Resident set size.

              * VmData, VmStk, VmExe: Size of data, stack, and text segments.

              * VmLib: Shared library code size.

              * VmPTE: Page table entries size (since Linux 2.6.10).

              * VmPMD: Size of second-level page tables (since Linux 4.0).

              * VmSwap: Swapped-out virtual memory size by  anonymous  private
                pages; shmem swap usage is not included (since Linux 2.6.34).

              * Threads: Number of threads in process containing this thread.

              * SigQ:  This  field  contains  two slash-separated numbers that
                relate to queued signals for the real user ID of this process.
                The  first  of these is the number of currently queued signals
                for this real user ID, and the second is the resource limit on
                the  number  of  queued  signals  for  this  process  (see the
                description of RLIMIT_SIGPENDING in getrlimit(2)).

              * SigPnd, ShdPnd: Number of signals pending for thread  and  for
                process as a whole (see pthreads(7) and signal(7)).

              * SigBlk,   SigIgn,   SigCgt:  Masks  indicating  signals  being
                blocked, ignored, and caught (see signal(7)).

              * CapInh, CapPrm,  CapEff:  Masks  of  capabilities  enabled  in
                inheritable,  permitted,  and  effective  sets  (see capabili-
                ties(7)).

              * CapBnd: Capability Bounding set (since Linux 2.6.26, see capa-
                bilities(7)).

              * CapAmb: Ambient capability set (since Linux 4.3, see capabili-
                ties(7)).

              * Seccomp: Seccomp mode of the process  (since  Linux  3.8,  see
                seccomp(2)).   0  means  SECCOMP_MODE_DISABLED;  1  means SEC-
                COMP_MODE_STRICT; 2 means SECCOMP_MODE_FILTER.  This field  is
                provided  only if the kernel was built with the CONFIG_SECCOMP
                kernel configuration option enabled.

              * Cpus_allowed: Mask of CPUs  on  which  this  process  may  run
                (since Linux 2.6.24, see cpuset(7)).

              * Cpus_allowed_list:  Same  as  previous,  but  in "list format"
                (since Linux 2.6.26, see cpuset(7)).

              * Mems_allowed: Mask of memory nodes  allowed  to  this  process
                (since Linux 2.6.24, see cpuset(7)).

              * Mems_allowed_list:  Same  as  previous,  but  in "list format"
                (since Linux 2.6.26, see cpuset(7)).

              * voluntary_ctxt_switches, nonvoluntary_ctxt_switches: Number of
                voluntary   and  involuntary  context  switches  (since  Linux
                2.6.23).

       /proc/[pid]/syscall (since Linux 2.6.27)
              This file exposes the system call number and argument  registers
              for  the  system  call  currently being executed by the process,
              followed by the values of the stack pointer and program  counter
              registers.   The  values  of  all  six  argument  registers  are
              exposed, although most system calls use fewer registers.

              If the process is blocked, but not in a system  call,  then  the
              file displays -1 in place of the system call number, followed by
              just the values of the stack pointer and  program  counter.   If
              process  is  not blocked, then the file contains just the string
              "running".

              This file is present only if the kernel was configured with CON-
              FIG_HAVE_ARCH_TRACEHOOK.

       /proc/[pid]/task (since Linux 2.6.0-test6)
              This  is  a  directory  that  contains one subdirectory for each
              thread in the process.  The name of  each  subdirectory  is  the
              numerical  thread  ID  ([tid])  of  the  thread (see gettid(2)).
              Within each of these subdirectories, there is  a  set  of  files
              with the same names and contents as under the /proc/[pid] direc-
              tories.  For attributes that are shared by all threads, the con-
              tents  for each of the files under the task/[tid] subdirectories
              will be the same as in the  corresponding  file  in  the  parent
              /proc/[pid]  directory (e.g., in a multithreaded process, all of
              the task/[tid]/cwd  files  will  have  the  same  value  as  the
              /proc/[pid]/cwd  file  in the parent directory, since all of the
              threads in a process share a working directory).  For attributes
              that are distinct for each thread, the corresponding files under
              task/[tid] may have different values (e.g.,  various  fields  in
              each  of  the  task/[tid]/status files may be different for each
              thread).

              In a multithreaded process, the contents of the /proc/[pid]/task
              directory  are not available if the main thread has already ter-
              minated (typically by calling pthread_exit(3)).

       /proc/[pid]/timers (since Linux 3.10)
              A list of the POSIX timers for  this  process.   Each  timer  is
              listed with a line that starts with the string "ID:".  For exam-
              ple:

                  ID: 1
                  signal: 60/00007fff86e452a8
                  notify: signal/pid.2634
                  ClockID: 0
                  ID: 0
                  signal: 60/00007fff86e452a8
                  notify: signal/pid.2634
                  ClockID: 1

              The lines shown for each timer have the following meanings:

              ID     The ID for this timer.  This is not the same as the timer
                     ID  returned  by  timer_create(2); rather, it is the same
                     kernel-internal ID that is available via  the  si_timerid
                     field of the siginfo_t structure (see sigaction(2)).

              signal This is the signal number that this timer uses to deliver
                     notifications  followed  by  a  slash,   and   then   the
                     sigev_value  value supplied to the signal handler.  Valid
                     only for timers that notify via a signal.

              notify The part before the slash specifies  the  mechanism  that
                     this  timer  uses to deliver notifications, and is one of
                     "thread", "signal", or "none".  Immediately following the
                     slash   is  either  the  string  "tid"  for  timers  with
                     SIGEV_THREAD_ID notification, or "pid"  for  timers  that
                     notify by other mechanisms.  Following the "." is the PID
                     of the process (or the kernel thread ID  of  the  thread)
                     that  will  be  delivered  a signal if the timer delivers
                     notifications via a signal.

              ClockID
                     This field identifies the clock that the timer  uses  for
                     measuring  time.   For most clocks, this is a number that
                     matches one of the user-space CLOCK_*  constants  exposed
                     via  <time.h>.   CLOCK_PROCESS_CPUTIME_ID  timers display
                     with    a    value    of    -6     in     this     field.
                     CLOCK_THREAD_CPUTIME_ID timers display with a value of -2
                     in this field.

              This file is available only when the kernel was configured  with
              CONFIG_CHECKPOINT_RESTORE.

       /proc/[pid]/uid_map, /proc/[pid]/gid_map (since Linux 3.5)
              See user_namespaces(7).

       /proc/[pid]/wchan (since Linux 2.6.0)
              The  symbolic  name  corresponding to the location in the kernel
              where the process is sleeping.

       /proc/apm
              Advanced power management version and battery  information  when
              CONFIG_APM is defined at kernel compilation time.

       /proc/buddyinfo
              This file contains information which is used for diagnosing mem-
              ory fragmentation issues.  Each line starts with the identifica-
              tion  of  the node and the name of the zone which together iden-
              tify a memory region This is  then  followed  by  the  count  of
              available  chunks  of  a  certain order in which these zones are
              split.  The size in bytes of a certain order  is  given  by  the
              formula:

                  (2^order) * PAGE_SIZE

              The  binary  buddy  allocator  algorithm  inside the kernel will
              split one chunk into two chunks of a smaller  order  (thus  with
              half  the size) or combine two contiguous chunks into one larger
              chunk of a higher order (thus with double the size)  to  satisfy
              allocation  requests  and  to counter memory fragmentation.  The
              order matches the column number, when starting to count at zero.

              For example on a x86_64 system:

  Node 0, zone     DMA     1    1    1    0    2    1    1    0    1    1    3
  Node 0, zone   DMA32    65   47    4   81   52   28   13   10    5    1  404
  Node 0, zone  Normal   216   55  189  101   84   38   37   27    5    3  587

              In this example, there is one node containing  three  zones  and
              there are 11 different chunk sizes.  If the page size is 4 kilo-
              bytes, then the first zone called  DMA  (on  x86  the  first  16
              megabyte  of memory) has 1 chunk of 4 kilobytes (order 0) avail-
              able and has 3 chunks of 4 megabytes (order 10) available.

              If the memory is heavily fragmented,  the  counters  for  higher
              order  chunks  will  be  zero and allocation of large contiguous
              areas will fail.

              Further information about the zones can be found in  /proc/zone-
              info.

       /proc/bus
              Contains subdirectories for installed busses.

       /proc/bus/pccard
              Subdirectory  for  PCMCIA  devices  when CONFIG_PCMCIA is set at
              kernel compilation time.

       /proc/bus/pccard/drivers

       /proc/bus/pci
              Contains various bus subdirectories and pseudo-files  containing
              information  about  PCI  busses,  installed  devices, and device
              drivers.  Some of these files are not ASCII.

       /proc/bus/pci/devices
              Information about PCI devices.  They  may  be  accessed  through
              lspci(8) and setpci(8).

       /proc/cmdline
              Arguments  passed  to the Linux kernel at boot time.  Often done
              via a boot manager such as lilo(8) or grub(8).

       /proc/config.gz (since Linux 2.6)
              This file exposes the configuration options that  were  used  to
              build  the  currently running kernel, in the same format as they
              would be shown in the .config file that resulted when  configur-
              ing  the  kernel  (using make xconfig, make config, or similar).
              The file contents are compressed;  view  or  search  them  using
              zcat(1)  and  zgrep(1).  As long as no changes have been made to
              the following file, the contents of /proc/config.gz are the same
              as those provided by :

                  cat /lib/modules/$(uname -r)/build/.config

              /proc/config.gz  is  provided  only  if the kernel is configured
              with CONFIG_IKCONFIG_PROC.

       /proc/crypto
              A list of the ciphers provided by the kernel  crypto  API.   For
              details,  see  the  kernel Linux Kernel Crypto API documentation
              available under the kernel source  directory  Documentation/Doc-
              Book.   (That documentation can be built using a command such as
              make htmldocs in the root directory of the kernel source tree.)

       /proc/cpuinfo
              This is a collection of CPU and  system  architecture  dependent
              items,  for  each  supported architecture a different list.  Two
              common  entries  are  processor  which  gives  CPU  number   and
              bogomips;  a  system  constant  that is calculated during kernel
              initialization.  SMP machines have  information  for  each  CPU.
              The lscpu(1) command gathers its information from this file.

       /proc/devices
              Text  listing  of  major numbers and device groups.  This can be
              used by MAKEDEV scripts for consistency with the kernel.

       /proc/diskstats (since Linux 2.5.69)
              This file contains disk I/O statistics  for  each  disk  device.
              See  the  Linux kernel source file Documentation/iostats.txt for
              further information.

       /proc/dma
              This is a list of the registered ISA DMA (direct memory  access)
              channels in use.

       /proc/driver
              Empty subdirectory.

       /proc/execdomains
              List of the execution domains (ABI personalities).

       /proc/fb
              Frame buffer information when CONFIG_FB is defined during kernel
              compilation.

       /proc/filesystems
              A text listing of the filesystems which  are  supported  by  the
              kernel,  namely  filesystems which were compiled into the kernel
              or  whose  kernel  modules  are  currently  loaded.   (See  also
              filesystems(5).)   If  a filesystem is marked with "nodev", this
              means that it does not require a  block  device  to  be  mounted
              (e.g., virtual filesystem, network filesystem).

              Incidentally, this file may be used by mount(8) when no filesys-
              tem is specified and it didn't manage to determine the  filesys-
              tem  type.   Then  filesystems  contained in this file are tried
              (excepted those that are marked with "nodev").

       /proc/fs
              Contains subdirectories that in turn contain files with informa-
              tion about (certain) mounted filesystems.

       /proc/ide
              This  directory  exists  on systems with the IDE bus.  There are
              directories for each IDE channel  and  attached  device.   Files
              include:

                  cache              buffer size in KB
                  capacity           number of sectors
                  driver             driver version
                  geometry           physical and logical geometry
                  identify           in hexadecimal
                  media              media type
                  model              manufacturer's model number
                  settings           drive settings
                  smart_thresholds   in hexadecimal
                  smart_values       in hexadecimal

              The  hdparm(8)  utility provides access to this information in a
              friendly format.

       /proc/interrupts
              This is used to record the number of interrupts per CPU  per  IO
              device.   Since  Linux 2.6.24, for the i386 and x86_64 architec-
              tures, at least, this also includes interrupts internal  to  the
              system  (that is, not associated with a device as such), such as
              NMI (nonmaskable interrupt), LOC (local  timer  interrupt),  and
              for  SMP  systems,  TLB (TLB flush interrupt), RES (rescheduling
              interrupt), CAL (remote function call interrupt),  and  possibly
              others.  Very easy to read formatting, done in ASCII.

       /proc/iomem
              I/O memory map in Linux 2.4.

       /proc/ioports
              This is a list of currently registered Input-Output port regions
              that are in use.

       /proc/kallsyms (since Linux 2.5.71)
              This holds the kernel exported symbol definitions  used  by  the
              modules(X)  tools to dynamically link and bind loadable modules.
              In Linux 2.5.47 and earlier, a similar file with  slightly  dif-
              ferent syntax was named ksyms.

       /proc/kcore
              This  file  represents  the physical memory of the system and is
              stored in the ELF core file format.  With this pseudo-file,  and
              an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be
              used to examine the current state of any kernel data structures.

              The total length of the file is  the  size  of  physical  memory
              (RAM) plus 4KB.

       /proc/kmsg
              This  file  can  be used instead of the syslog(2) system call to
              read kernel messages.  A process must have superuser  privileges
              to  read  this file, and only one process should read this file.
              This file should not be read if  a  syslog  process  is  running
              which uses the syslog(2) system call facility to log kernel mes-
              sages.

              Information in this file is retrieved with the dmesg(1) program.

       /proc/kpagecount (since Linux 2.6.25)
              This file contains a 64-bit count of the number  of  times  each
              physical page frame is mapped, indexed by page frame number (see
              the discussion of /proc/[pid]/pagemap).

              The  /proc/kpagecount  file  is  present  only   if   the   CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/kpageflags (since Linux 2.6.25)
              This  file  contains 64-bit masks corresponding to each physical
              page frame; it is indexed by page frame number (see the  discus-
              sion of /proc/[pid]/pagemap).  The bits are as follows:

                   0 - KPF_LOCKED
                   1 - KPF_ERROR
                   2 - KPF_REFERENCED
                   3 - KPF_UPTODATE
                   4 - KPF_DIRTY
                   5 - KPF_LRU
                   6 - KPF_ACTIVE
                   7 - KPF_SLAB
                   8 - KPF_WRITEBACK
                   9 - KPF_RECLAIM
                  10 - KPF_BUDDY
                  11 - KPF_MMAP           (since Linux 2.6.31)
                  12 - KPF_ANON           (since Linux 2.6.31)
                  13 - KPF_SWAPCACHE      (since Linux 2.6.31)
                  14 - KPF_SWAPBACKED     (since Linux 2.6.31)
                  15 - KPF_COMPOUND_HEAD  (since Linux 2.6.31)
                  16 - KPF_COMPOUND_TAIL  (since Linux 2.6.31)
                  16 - KPF_HUGE           (since Linux 2.6.31)
                  18 - KPF_UNEVICTABLE    (since Linux 2.6.31)
                  19 - KPF_HWPOISON       (since Linux 2.6.31)
                  20 - KPF_NOPAGE         (since Linux 2.6.31)
                  21 - KPF_KSM            (since Linux 2.6.32)
                  22 - KPF_THP            (since Linux 3.4)

              For  further details on the meanings of these bits, see the ker-
              nel source  file  Documentation/vm/pagemap.txt.   Before  kernel
              2.6.29,  KPF_WRITEBACK,  KPF_RECLAIM,  KPF_BUDDY, and KPF_LOCKED
              did not report correctly.

              The  /proc/kpageflags  file  is  present  only   if   the   CON-
              FIG_PROC_PAGE_MONITOR kernel configuration option is enabled.

       /proc/ksyms (Linux 1.1.23-2.5.47)
              See /proc/kallsyms.

       /proc/loadavg
              The  first  three  fields  in this file are load average figures
              giving the number of jobs in the run queue (state R) or  waiting
              for disk I/O (state D) averaged over 1, 5, and 15 minutes.  They
              are the same as the load average numbers given by uptime(1)  and
              other  programs.  The fourth field consists of two numbers sepa-
              rated by a slash (/).  The first of these is the number of  cur-
              rently runnable kernel scheduling entities (processes, threads).
              The value after the slash is the  number  of  kernel  scheduling
              entities that currently exist on the system.  The fifth field is
              the PID of the process that was most  recently  created  on  the
              system.

       /proc/locks
              This  file  shows current file locks (flock(2) and fcntl(2)) and
              leases (fcntl(2)).

       /proc/malloc (only up to and including Linux 2.2)
              This file is present only  if  CONFIG_DEBUG_MALLOC  was  defined
              during compilation.

       /proc/meminfo
              This  file  reports statistics about memory usage on the system.
              It is used by free(1) to report the amount of free and used mem-
              ory (both physical and swap) on the system as well as the shared
              memory and buffers used by the kernel.  Each line  of  the  file
              consists  of a parameter name, followed by a colon, the value of
              the parameter, and an option unit of measurement  (e.g.,  "kB").
              The  list  below  describes  the  parameter names and the format
              specifier required to read the field  value.   Except  as  noted
              below,  all of the fields have been present since at least Linux
              2.6.0.  Some fields are displayed only if the kernel was config-
              ured  with  various options; those dependencies are noted in the
              list.

              MemTotal %lu
                     Total usable RAM (i.e., physical RAM minus a few reserved
                     bits and the kernel binary code).

              MemFree %lu
                     The sum of LowFree+HighFree.

              Buffers %lu
                     Relatively  temporary  storage  for  raw disk blocks that
                     shouldn't get tremendously large (20MB or so).

              Cached %lu
                     In-memory cache for files read from the  disk  (the  page
                     cache).  Doesn't include SwapCached.

              SwapCached %lu
                     Memory  that once was swapped out, is swapped back in but
                     still also is in the swap file.  (If memory  pressure  is
                     high,  these  pages  don't  need  to be swapped out again
                     because they are already in the swap  file.   This  saves
                     I/O.)

              Active %lu
                     Memory  that  has been used more recently and usually not
                     reclaimed unless absolutely necessary.

              Inactive %lu
                     Memory which has been less recently  used.   It  is  more
                     eligible to be reclaimed for other purposes.

              Active(anon) %lu (since Linux 2.6.28)
                     [To be documented.]

              Inactive(anon) %lu (since Linux 2.6.28)
                     [To be documented.]

              Active(file) %lu (since Linux 2.6.28)
                     [To be documented.]

              Inactive(file) %lu (since Linux 2.6.28)
                     [To be documented.]

              Unevictable %lu (since Linux 2.6.28)
                     (From  Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU was
                     required.)  [To be documented.]

              Mlocked %lu (since Linux 2.6.28)
                     (From Linux 2.6.28 to 2.6.30, CONFIG_UNEVICTABLE_LRU  was
                     required.)  [To be documented.]

              HighTotal %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Total amount of highmem.  Highmem  is  all  memory  above
                     ~860MB  of physical memory.  Highmem areas are for use by
                     user-space programs, or for the page cache.   The  kernel
                     must  use  tricks to access this memory, making it slower
                     to access than lowmem.

              HighFree %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Amount of free highmem.

              LowTotal %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Total amount of lowmem.  Lowmem is memory  which  can  be
                     used  for everything that highmem can be used for, but it
                     is also available for the kernel's use for its  own  data
                     structures.   Among many other things, it is where every-
                     thing from Slab is allocated.   Bad  things  happen  when
                     you're out of lowmem.

              LowFree %lu
                     (Starting with Linux 2.6.19, CONFIG_HIGHMEM is required.)
                     Amount of free lowmem.

              MmapCopy %lu (since Linux 2.6.29)
                     (CONFIG_MMU is required.)  [To be documented.]

              SwapTotal %lu
                     Total amount of swap space available.

              SwapFree %lu
                     Amount of swap space that is currently unused.

              Dirty %lu
                     Memory which is waiting to get written back to the disk.

              Writeback %lu
                     Memory which is actively being written back to the disk.

              AnonPages %lu (since Linux 2.6.18)
                     Non-file backed pages mapped into user-space page tables.

              Mapped %lu
                     Files which have been mapped into memory (with  mmap(2)),
                     such as libraries.

              Shmem %lu (since Linux 2.6.32)
                     [To be documented.]

              Slab %lu
                     In-kernel data structures cache.

              SReclaimable %lu (since Linux 2.6.19)
                     Part of Slab, that might be reclaimed, such as caches.

              SUnreclaim %lu (since Linux 2.6.19)
                     Part  of  Slab,  that cannot be reclaimed on memory pres-
                     sure.

              KernelStack %lu (since Linux 2.6.32)
                     Amount of memory allocated to kernel stacks.

              PageTables %lu (since Linux 2.6.18)
                     Amount of memory dedicated to the lowest  level  of  page
                     tables.

              Quicklists %lu (since Linux 2.6.27)
                     (CONFIG_QUICKLIST is required.)  [To be documented.]

              NFS_Unstable %lu (since Linux 2.6.18)
                     NFS  pages  sent  to the server, but not yet committed to
                     stable storage.

              Bounce %lu (since Linux 2.6.18)
                     Memory used for block device "bounce buffers".

              WritebackTmp %lu (since Linux 2.6.26)
                     Memory used by FUSE for temporary writeback buffers.

              CommitLimit %lu (since Linux 2.6.10)
                     This is the total amount of memory currently available to
                     be allocated on the system, expressed in kilobytes.  This
                     limit is adhered to only if strict overcommit  accounting
                     is  enabled  (mode  2 in /proc/sys/vm/overcommit_memory).
                     The  limit  is  calculated  according  to   the   formula
                     described under /proc/sys/vm/overcommit_memory.  For fur-
                     ther details,  see  the  kernel  source  file  Documenta-
                     tion/vm/overcommit-accounting.

              Committed_AS %lu
                     The  amount  of memory presently allocated on the system.
                     The committed memory is a sum of all of the memory  which
                     has  been allocated by processes, even if it has not been
                     "used" by them as of yet.  A process which allocates  1GB
                     of  memory (using malloc(3) or similar), but touches only
                     300MB of that memory will show up as using only 300MB  of
                     memory even if it has the address space allocated for the
                     entire 1GB.

                     This 1GB is memory which has been "committed" to  by  the
                     VM and can be used at any time by the allocating applica-
                     tion.  With strict overcommit enabled on the system (mode
                     2  in  IR  /proc/sys/vm/overcommit_memory  ), allocations
                     which would exceed the CommitLimit will not be permitted.
                     This  is  useful if one needs to guarantee that processes
                     will not fail due to lack of memory once that memory  has
                     been successfully allocated.

              VmallocTotal %lu
                     Total size of vmalloc memory area.

              VmallocUsed %lu
                     Amount of vmalloc area which is used.

              VmallocChunk %lu
                     Largest contiguous block of vmalloc area which is free.

              HardwareCorrupted %lu (since Linux 2.6.32)
                     (CONFIG_MEMORY_FAILURE is required.)  [To be documented.]

              AnonHugePages %lu (since Linux 2.6.38)
                     (CONFIG_TRANSPARENT_HUGEPAGE   is   required.)   Non-file
                     backed huge pages mapped into user-space page tables.

              HugePages_Total %lu
                     (CONFIG_HUGETLB_PAGE is required.)  The size of the  pool
                     of huge pages.

              HugePages_Free %lu
                     (CONFIG_HUGETLB_PAGE  is  required.)   The number of huge
                     pages in the pool that are not yet allocated.

              HugePages_Rsvd %lu (since Linux 2.6.17)
                     (CONFIG_HUGETLB_PAGE is required.)  This is the number of
                     huge  pages  for  which a commitment to allocate from the
                     pool has been made, but no allocation has yet been  made.
                     These  reserved  huge pages guarantee that an application
                     will be able to allocate a huge page  from  the  pool  of
                     huge pages at fault time.

              HugePages_Surp %lu (since Linux 2.6.24)
                     (CONFIG_HUGETLB_PAGE is required.)  This is the number of
                     huge   pages   in   the   pool   above   the   value   in
                     /proc/sys/vm/nr_hugepages.  The maximum number of surplus
                     huge  pages  is  controlled  by  /proc/sys/vm/nr_overcom-
                     mit_hugepages.

              Hugepagesize %lu
                     (CONFIG_HUGETLB_PAGE  is  required.)   The  size  of huge
                     pages.

       /proc/modules
              A text list of the modules that have been loaded by the  system.
              See also lsmod(8).

       /proc/mounts
              Before  kernel  2.4.19, this file was a list of all the filesys-
              tems currently mounted on the system.  With the introduction  of
              per-process mount namespaces in Linux 2.4.19, this file became a
              link to /proc/self/mounts, which lists the mount points  of  the
              process's own mount namespace.  The format of this file is docu-
              mented in fstab(5).

       /proc/mtrr
              Memory Type Range Registers.  See the Linux kernel  source  file
              Documentation/mtrr.txt for details.

       /proc/net
              various  net  pseudo-files, all of which give the status of some
              part of the networking layer.  These files contain ASCII  struc-
              tures  and  are,  therefore, readable with cat(1).  However, the
              standard netstat(8) suite provides much cleaner access to  these
              files.

       /proc/net/arp
              This  holds  an ASCII readable dump of the kernel ARP table used
              for address resolutions.  It will show both dynamically  learned
              and preprogrammed ARP entries.  The format is:

        IP address     HW type   Flags     HW address          Mask   Device
        192.168.0.50   0x1       0x2       00:50:BF:25:68:F3   *      eth0
        192.168.0.250  0x1       0xc       00:00:00:00:00:00   *      eth0

              Here "IP address" is the IPv4 address of the machine and the "HW
              type" is the hardware type of the  address  from  RFC 826.   The
              flags are the internal flags of the ARP structure (as defined in
              /usr/include/linux/if_arp.h) and the "HW address"  is  the  data
              link layer mapping for that IP address if it is known.

       /proc/net/dev
              The  dev pseudo-file contains network device status information.
              This gives the number of received and sent packets,  the  number
              of  errors and collisions and other basic statistics.  These are
              used by the ifconfig(8) program to report  device  status.   The
              format is:

 Inter-|   Receive                                                |  Transmit
  face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
     lo: 2776770   11307    0    0    0     0          0         0  2776770   11307    0    0    0     0       0          0
   eth0: 1215645    2751    0    0    0     0          0         0  1782404    4324    0    0    0   427       0          0
   ppp0: 1622270    5552    1    0    0     0          0         0   354130    5669    0    0    0     0       0          0
   tap0:    7714      81    0    0    0     0          0         0     7714      81    0    0    0     0       0          0

       /proc/net/dev_mcast
              Defined in /usr/src/linux/net/core/dev_mcast.c:
                   indx interface_name  dmi_u dmi_g dmi_address
                   2    eth0            1     0     01005e000001
                   3    eth1            1     0     01005e000001
                   4    eth2            1     0     01005e000001

       /proc/net/igmp
              Internet     Group     Management    Protocol.     Defined    in
              /usr/src/linux/net/core/igmp.c.

       /proc/net/rarp
              This file uses the same format as the arp file and contains  the
              current reverse mapping database used to provide rarp(8) reverse
              address lookup services.  If RARP is  not  configured  into  the
              kernel, this file will not be present.

       /proc/net/raw
              Holds  a  dump of the RAW socket table.  Much of the information
              is not of use apart from debugging.  The "sl" value is the  ker-
              nel  hash  slot for the socket, the "local_address" is the local
              address and protocol number pair.  "St" is the  internal  status
              of  the  socket.  The "tx_queue" and "rx_queue" are the outgoing
              and incoming data queue in terms of kernel  memory  usage.   The
              "tr", "tm->when", and "rexmits" fields are not used by RAW.  The
              "uid" field holds the  effective  UID  of  the  creator  of  the
              socket.

       /proc/net/snmp
              This file holds the ASCII data needed for the IP, ICMP, TCP, and
              UDP management information bases for an SNMP agent.

       /proc/net/tcp
              Holds a dump of the TCP socket table.  Much of  the  information
              is  not of use apart from debugging.  The "sl" value is the ker-
              nel hash slot for the socket, the "local_address" is  the  local
              address  and  port number pair.  The "rem_address" is the remote
              address and port number pair (if connected).  "St" is the inter-
              nal status of the socket.  The "tx_queue" and "rx_queue" are the
              outgoing and incoming data  queue  in  terms  of  kernel  memory
              usage.  The "tr", "tm->when", and "rexmits" fields hold internal
              information of the kernel socket state and are useful  only  for
              debugging.   The "uid" field holds the effective UID of the cre-
              ator of the socket.

       /proc/net/udp
              Holds a dump of the UDP socket table.  Much of  the  information
              is  not of use apart from debugging.  The "sl" value is the ker-
              nel hash slot for the socket, the "local_address" is  the  local
              address  and  port number pair.  The "rem_address" is the remote
              address and port number pair (if connected).  "St" is the inter-
              nal status of the socket.  The "tx_queue" and "rx_queue" are the
              outgoing and incoming data  queue  in  terms  of  kernel  memory
              usage.   The "tr", "tm->when", and "rexmits" fields are not used
              by UDP.  The "uid" field holds the effective UID of the  creator
              of the socket.  The format is:

 sl  local_address rem_address   st tx_queue rx_queue tr rexmits  tm->when uid
  1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
  1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
  1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0

       /proc/net/unix
              Lists  the  UNIX  domain  sockets  present within the system and
              their status.  The format is:
              Num RefCount Protocol Flags    Type St Path
               0: 00000002 00000000 00000000 0001 03
               1: 00000001 00000000 00010000 0001 01 /dev/printer

              The fields are as follows:

              Num:      the kernel table slot number.

              RefCount: the number of users of the socket.

              Protocol: currently always 0.

              Flags:    the internal kernel flags holding the  status  of  the
                        socket.

              Type:     the  socket  type.   For  SOCK_STREAM sockets, this is
                        0001; for SOCK_DGRAM sockets,  it  is  0002;  and  for
                        SOCK_SEQPACKET sockets, it is 0005.

              St:       the internal state of the socket.

              Path:     the bound path (if any) of the socket.  Sockets in the
                        abstract namespace are included in the list,  and  are
                        shown  with  a  Path that commences with the character
                        '@'.

       /proc/net/netfilter/nfnetlink_queue
              This file contains information about netfilter userspace  queue-
              ing,  if  used.  Each line represents a queue.  Queues that have
              not been subscribed to by userspace are not shown.

                 1   4207     0  2 65535     0     0        0  1
                (1)   (2)    (3)(4)  (5)    (6)   (7)      (8)

              The fields in each line are:

              (1)  The ID of the queue.  This matches what is specified in the
                   --queue-num  or  --queue-balance options to the iptables(8)
                   NFQUEUE target.  See iptables-extensions(8) for more infor-
                   mation.

              (2)  The netlink port ID subscribed to the queue.

              (3)  The  number  of  packets currently queued and waiting to be
                   processed by the application.

              (4)  The copy mode of the queue.  It is either 1 (metadata only)
                   or 2 (also copy payload data to userspace).

              (5)  Copy  range;  that  is,  how  many  bytes of packet payload
                   should be copied to userspace at most.

              (6)  queue dropped.  Number of packets that had to be dropped by
                   the kernel because too many packets are already waiting for
                   userspace to send back the mandatory accept/drop verdicts.

              (7)  queue user dropped.  Number of packets  that  were  dropped
                   within  the  netlink  subsystem.  Such drops usually happen
                   when the corresponding socket  buffer  is  full;  that  is,
                   userspace is not able to read messages fast enough.

              (8)  sequence  number.  Every queued packet is associated with a
                   (32-bit) monotonically-increasing  sequence  number.   This
                   shows the ID of the most recent packet queued.

              The  last  number  exists  only for compatibility reasons and is
              always 1.

       /proc/partitions
              Contains the major and minor numbers of each partition  as  well
              as the number of 1024-byte blocks and the partition name.

       /proc/pci
              This  is  a  listing of all PCI devices found during kernel ini-
              tialization and their configuration.

              This file has been deprecated in favor of a new /proc  interface
              for  PCI  (/proc/bus/pci).   It  became  optional  in  Linux 2.2
              (available with CONFIG_PCI_OLD_PROC set at kernel  compilation).
              It  became  once more nonoptionally enabled in Linux 2.4.  Next,
              it was deprecated  in  Linux  2.6  (still  available  with  CON-
              FIG_PCI_LEGACY_PROC  set),  and finally removed altogether since
              Linux 2.6.17.

       /proc/profile (since Linux 2.4)
              This file is present only if the kernel was booted with the pro-
              file=1  command-line option.  It exposes kernel profiling infor-
              mation in a binary format for use  by  readprofile(1).   Writing
              (e.g.,  an empty string) to this file resets the profiling coun-
              ters; on some architectures, writing a binary integer "profiling
              multiplier"  of  size  sizeof(int)  sets the profiling interrupt
              frequency.

       /proc/scsi
              A directory with the scsi mid-level pseudo-file and various SCSI
              low-level driver directories, which contain a file for each SCSI
              host in this system, all of which give the status of  some  part
              of  the SCSI IO subsystem.  These files contain ASCII structures
              and are, therefore, readable with cat(1).

              You can also write to some of the files to reconfigure the  sub-
              system or switch certain features on or off.

       /proc/scsi/scsi
              This  is a listing of all SCSI devices known to the kernel.  The
              listing is similar to the one seen  during  bootup.   scsi  cur-
              rently  supports only the add-single-device command which allows
              root to add a hotplugged device to the list of known devices.

              The command

                  echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi

              will cause host scsi1 to scan on SCSI channel 0 for a device  on
              ID  5 LUN 0.  If there is already a device known on this address
              or the address is invalid, an error will be returned.

       /proc/scsi/[drivername]
              [drivername]  can  currently  be  NCR53c7xx,  aha152x,  aha1542,
              aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000,
              pas16, qlogic, scsi_debug, seagate, t128,  u15-24f,  ultrastore,
              or  wd7000.  These directories show up for all drivers that reg-
              istered at least one SCSI HBA.   Every  directory  contains  one
              file  per  registered  host.  Every host-file is named after the
              number the host was assigned during initialization.

              Reading these files will usually show driver and host configura-
              tion, statistics, and so on.

              Writing  to  these  files  allows  different things on different
              hosts.  For example, with the latency  and  nolatency  commands,
              root  can  switch on and off command latency measurement code in
              the eata_dma driver.  With the lockup and unlock commands,  root
              can control bus lockups simulated by the scsi_debug driver.

       /proc/self
              This  directory  refers  to  the  process  accessing  the  /proc
              filesystem, and is identical to the /proc directory named by the
              process ID of the same process.

       /proc/slabinfo
              Information  about  kernel caches.  Since Linux 2.6.16 this file
              is present only if the CONFIG_SLAB kernel  configuration  option
              is enabled.  The columns in /proc/slabinfo are:

                  cache-name
                  num-active-objs
                  total-objs
                  object-size
                  num-active-slabs
                  total-slabs
                  num-pages-per-slab

              See slabinfo(5) for details.

       /proc/stat
              kernel/system  statistics.   Varies  with  architecture.  Common
              entries include:

              cpu  3357 0 4313 1362393
                     The  amount  of  time,  measured  in  units  of   USER_HZ
                     (1/100ths   of   a  second  on  most  architectures,  use
                     sysconf(_SC_CLK_TCK) to obtain the right value), that the
                     system spent in various states:

                     user   (1) Time spent in user mode.

                     nice   (2)  Time  spent  in  user  mode with low priority
                            (nice).

                     system (3) Time spent in system mode.

                     idle   (4) Time spent  in  the  idle  task.   This  value
                            should  be  USER_HZ  times the second entry in the
                            /proc/uptime pseudo-file.

                     iowait (since Linux 2.5.41)
                            (5) Time waiting for I/O to complete.

                     irq (since Linux 2.6.0-test4)
                            (6) Time servicing interrupts.

                     softirq (since Linux 2.6.0-test4)
                            (7) Time servicing softirqs.

                     steal (since Linux 2.6.11)
                            (8) Stolen time, which is the time spent in  other
                            operating  systems  when  running in a virtualized
                            environment

                     guest (since Linux 2.6.24)
                            (9) Time spent running a  virtual  CPU  for  guest
                            operating  systems  under the control of the Linux
                            kernel.

                     guest_nice (since Linux 2.6.33)
                            (10) Time spent running a niced guest (virtual CPU
                            for  guest  operating systems under the control of
                            the Linux kernel).

              page 5741 1808
                     The number of pages the system paged in  and  the  number
                     that were paged out (from disk).

              swap 1 0
                     The  number  of  swap pages that have been brought in and
                     out.

              intr 1462898
                     This line shows counts of interrupts serviced since  boot
                     time,  for  each  of the possible system interrupts.  The
                     first column is the  total  of  all  interrupts  serviced
                     including  unnumbered  architecture  specific interrupts;
                     each subsequent column is the total for  that  particular
                     numbered interrupt.  Unnumbered interrupts are not shown,
                     only summed into the total.

              disk_io: (2,0):(31,30,5764,1,2) (3,0):...
                     (major,disk_idx):(noinfo,     read_io_ops,     blks_read,
                     write_io_ops, blks_written)
                     (Linux 2.4 only)

              ctxt 115315
                     The number of context switches that the system underwent.

              btime 769041601
                     boot   time,  in  seconds  since  the  Epoch,  1970-01-01
                     00:00:00 +0000 (UTC).

              processes 86031
                     Number of forks since boot.

              procs_running 6
                     Number of processes in  runnable  state.   (Linux  2.5.45
                     onward.)

              procs_blocked 2
                     Number  of processes blocked waiting for I/O to complete.
                     (Linux 2.5.45 onward.)

       /proc/swaps
              Swap areas in use.  See also swapon(8).

       /proc/sys
              This directory (present since 1.3.57) contains a number of files
              and  subdirectories  corresponding  to  kernel variables.  These
              variables can be read and sometimes  modified  using  the  /proc
              filesystem, and the (deprecated) sysctl(2) system call.

              String values may be terminated by either '\0' or '\n'.

              Integer  and  long values may be written either in decimal or in
              hexadecimal notation (e.g. 0x3FFF).  When writing multiple inte-
              ger or long values, these may be separated by any of the follow-
              ing whitespace characters: ' ', '\t', or '\n'.  Using other sep-
              arators leads to the error EINVAL.

       /proc/sys/abi (since Linux 2.4.10)
              This  directory may contain files with application binary infor-
              mation.   See  the   Linux   kernel   source   file   Documenta-
              tion/sysctl/abi.txt for more information.

       /proc/sys/debug
              This directory may be empty.

       /proc/sys/dev
              This   directory  contains  device-specific  information  (e.g.,
              dev/cdrom/info).  On some systems, it may be empty.

       /proc/sys/fs
              This directory contains the files and subdirectories for  kernel
              variables related to filesystems.

       /proc/sys/fs/binfmt_misc
              Documentation  for  files  in this directory can be found in the
              Linux kernel sources in Documentation/binfmt_misc.txt.

       /proc/sys/fs/dentry-state (since Linux 2.2)
              This file contains information about the status of the directory
              cache  (dcache).   The  file  contains  six  numbers, nr_dentry,
              nr_unused,  age_limit  (age  in  seconds),   want_pages   (pages
              requested by system) and two dummy values.

              * nr_dentry   is   the  number  of  allocated  dentries  (dcache
                entries).  This field is unused in Linux 2.2.

              * nr_unused is the number of unused dentries.

              * age_limit is the age in seconds after which dcache entries can
                be reclaimed when memory is short.

              * want_pages   is   nonzero   when   the   kernel   has   called
                shrink_dcache_pages() and the dcache isn't pruned yet.

       /proc/sys/fs/dir-notify-enable
              This file can be used to disable or enable the dnotify interface
              described  in  fcntl(2) on a system-wide basis.  A value of 0 in
              this file disables the interface, and a value of 1 enables it.

       /proc/sys/fs/dquot-max
              This file shows the maximum number of cached disk quota entries.
              On some (2.4) systems, it is not present.  If the number of free
              cached disk quota entries is very low and you have some  awesome
              number of simultaneous system users, you might want to raise the
              limit.

       /proc/sys/fs/dquot-nr
              This file shows the number of allocated disk quota  entries  and
              the number of free disk quota entries.

       /proc/sys/fs/epoll (since Linux 2.6.28)
              This  directory contains the file max_user_watches, which can be
              used to limit the amount of kernel memory consumed by the  epoll
              interface.  For further details, see epoll(7).

       /proc/sys/fs/file-max
              This  file  defines  a  system-wide  limit on the number of open
              files for all processes.  System calls that fail when encounter-
              ing  this  limit  fail  with  the error ENFILE.  (See also setr-
              limit(2), which can be used by a process to set the  per-process
              limit,  RLIMIT_NOFILE,  on the number of files it may open.)  If
              you get lots of error messages in the kernel log  about  running
              out  of  file  handles  (look  for "VFS: file-max limit <number>
              reached"), try increasing this value:

                  echo 100000 > /proc/sys/fs/file-max

              Privileged processes (CAP_SYS_ADMIN) can override  the  file-max
              limit.

       /proc/sys/fs/file-nr
              This  (read-only)  file  contains  three  numbers: the number of
              allocated file handles (i.e.,  the  number  of  files  presently
              opened); the number of free file handles; and the maximum number
              of file handles (i.e., the same value as /proc/sys/fs/file-max).
              If the number of allocated file handles is close to the maximum,
              you should consider increasing the maximum.  Before  Linux  2.6,
              the  kernel  allocated  file  handles dynamically, but it didn't
              free them again.  Instead the free file handles were kept  in  a
              list  for  reallocation; the "free file handles" value indicates
              the size of that list.  A large  number  of  free  file  handles
              indicates  that  there was a past peak in the usage of open file
              handles.  Since Linux 2.6, the kernel does deallocate freed file
              handles, and the "free file handles" value is always zero.

       /proc/sys/fs/inode-max (only present until Linux 2.2)
              This file contains the maximum number of in-memory inodes.  This
              value should be 3-4 times larger than  the  value  in  file-max,
              since  stdin,  stdout  and network sockets also need an inode to
              handle them.  When you regularly run out of inodes, you need  to
              increase this value.

              Starting  with  Linux  2.4, there is no longer a static limit on
              the number of inodes, and this file is removed.

       /proc/sys/fs/inode-nr
              This file contains the first two values from inode-state.

       /proc/sys/fs/inode-state
              This file contains  seven  numbers:  nr_inodes,  nr_free_inodes,
              preshrink, and four dummy values (always zero).

              nr_inodes  is  the  number  of  inodes the system has allocated.
              nr_free_inodes represents the number of free inodes.

              preshrink is nonzero when the nr_inodes > inode-max and the sys-
              tem  needs  to  prune the inode list instead of allocating more;
              since Linux 2.4, this field is a dummy value (always zero).

       /proc/sys/fs/inotify (since Linux 2.6.13)
              This     directory     contains     files     max_queued_events,
              max_user_instances,  and  max_user_watches,  that can be used to
              limit the amount of kernel memory consumed by the inotify inter-
              face.  For further details, see inotify(7).

       /proc/sys/fs/lease-break-time
              This file specifies the grace period that the kernel grants to a
              process holding a file lease (fcntl(2)) after it has sent a sig-
              nal to that process notifying it that another process is waiting
              to open the file.  If the lease holder does not remove or  down-
              grade  the  lease  within this grace period, the kernel forcibly
              breaks the lease.

       /proc/sys/fs/leases-enable
              This  file  can  be  used  to  enable  or  disable  file  leases
              (fcntl(2))  on  a  system-wide basis.  If this file contains the
              value 0, leases are disabled.  A nonzero value enables leases.

       /proc/sys/fs/mqueue (since Linux 2.6.6)
              This  directory  contains  files   msg_max,   msgsize_max,   and
              queues_max,  controlling  the  resources  used  by POSIX message
              queues.  See mq_overview(7) for details.

       /proc/sys/fs/nr_open (since Linux 2.6.25)
              This  file  imposes  ceiling  on  the   value   to   which   the
              RLIMIT_NOFILE  resource  limit can be raised (see getrlimit(2)).
              This ceiling is enforced for both  unprivileged  and  privileged
              process.   The  default  value in this file is 1048576.  (Before
              Linux 2.6.25, the ceiling for RLIMIT_NOFILE  was  hard-coded  to
              the same value.)

       /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
              These  files  allow you to change the value of the fixed UID and
              GID.  The default  is  65534.   Some  filesystems  support  only
              16-bit  UIDs  and  GIDs,  although in Linux UIDs and GIDs are 32
              bits.  When one of these  filesystems  is  mounted  with  writes
              enabled, any UID or GID that would exceed 65535 is translated to
              the overflow value before being written to disk.

       /proc/sys/fs/pipe-max-size (since Linux 2.6.35)
              The value in this file defines an upper limit  for  raising  the
              capacity  of  a  pipe using the fcntl(2) F_SETPIPE_SZ operation.
              This limit applies only to unprivileged processes.  The  default
              value  for  this  file is 1,048,576.  The value assigned to this
              file may be  rounded  upward,  to  reflect  the  value  actually
              employed  for  a  convenient  implementation.   To determine the
              rounded-up value,  display  the  contents  of  this  file  after
              assigning a value to it.  The minimum value that can be assigned
              to this file is the system page size.

       /proc/sys/fs/protected_hardlinks (since Linux 3.6)
              When the value in this file is 0, no restrictions are placed  on
              the  creation of hard links (i.e., this is the historical behav-
              ior before Linux 3.6).  When the value in this file is 1, a hard
              link  can be created to a target file only if one of the follow-
              ing conditions is true:

              *  The caller has the CAP_FOWNER capability.

              *  The filesystem UID of the process creating the  link  matches
                 the  owner  (UID) of the target file (as described in creden-
                 tials(7), a process's filesystem UID is normally the same  as
                 its effective UID).

              *  All of the following conditions are true:

                  o  the target is a regular file;

                  o  the  target  file  does not have its set-user-ID mode bit
                     enabled;

                  o  the target file does not have both its  set-group-ID  and
                     group-executable mode bits enabled; and

                  o  the  caller  has  permission to read and write the target
                     file (either via the file's permissions mask  or  because
                     it has suitable capabilities).

              The  default  value  in  this file is 0.  Setting the value to 1
              prevents a longstanding class of security issues caused by hard-
              link-based  time-of-check, time-of-use races, most commonly seen
              in world-writable directories such as /tmp.  The  common  method
              of  exploiting  this  flaw is to cross privilege boundaries when
              following a given hard link (i.e., a root process follows a hard
              link created by another user).  Additionally, on systems without
              separated partitions, this stops unauthorized users  from  "pin-
              ning"  vulnerable  set-user-ID  and  set-group-ID  files against
              being upgraded by  the  administrator,  or  linking  to  special
              files.

       /proc/sys/fs/protected_symlinks (since Linux 3.6)
              When  the value in this file is 0, no restrictions are placed on
              following symbolic links (i.e., this is the historical  behavior
              before  Linux  3.6).  When the value in this file is 1, symbolic
              links are followed only in the following circumstances:

              *  the filesystem UID of the process following the link  matches
                 the owner (UID) of the symbolic link (as described in creden-
                 tials(7), a process's filesystem UID is normally the same  as
                 its effective UID);

              *  the link is not in a sticky world-writable directory; or

              *  the  symbolic  link  and  its  parent directory have the same
                 owner (UID)

              A system call that fails to follow a symbolic  link  because  of
              the above restrictions returns the error EACCES in errno.

              The  default  value  in  this file is 0.  Setting the value to 1
              avoids a longstanding class of security issues based on time-of-
              check, time-of-use races when accessing symbolic links.

       /proc/sys/fs/suid_dumpable (since Linux 2.6.13)
              The  value  in  this  file is assigned to a process's "dumpable"
              flag in the circumstances described in prctl(2).  In effect, the
              value  in  this file determines whether core dump files are pro-
              duced for set-user-ID or otherwise  protected/tainted  binaries.
              Three different integer values can be specified:

              0 (default)
                     This  provides  the traditional (pre-Linux 2.6.13) behav-
                     ior.  A core dump will not  be  produced  for  a  process
                     which  has  changed  credentials  (by calling seteuid(2),
                     setgid(2), or similar, or by executing a  set-user-ID  or
                     set-group-ID  program) or whose binary does not have read
                     permission enabled.

              1 ("debug")
                     All processes dump core when possible.  The core dump  is
                     owned  by  the  filesystem user ID of the dumping process
                     and no security is applied.  This is intended for  system
                     debugging situations only.  Ptrace is unchecked.

              2 ("suidsafe")
                     Any  binary  which  normally would not be dumped (see "0"
                     above) is dumped readable by root only.  This allows  the
                     user  to  remove  the  core dump file but not to read it.
                     For security reasons core dumps in  this  mode  will  not
                     overwrite  one  another  or  other  files.   This mode is
                     appropriate when administrators are attempting  to  debug
                     problems in a normal environment.

                     Additionally, since Linux 3.6, /proc/sys/kernel/core_pat-
                     tern must either be an absolute pathname or a  pipe  com-
                     mand,  as  detailed in core(5).  Warnings will be written
                     to the kernel log if core_pattern does not  follow  these
                     rules, and no core dump will be produced.

       /proc/sys/fs/super-max
              This  file  controls the maximum number of superblocks, and thus
              the maximum number of mounted filesystems the kernel  can  have.
              You  need  increase  only  super-max  if  you need to mount more
              filesystems than the current value in super-max allows you to.

       /proc/sys/fs/super-nr
              This file contains the number of filesystems currently mounted.

       /proc/sys/kernel
              This directory contains files  controlling  a  range  of  kernel
              parameters, as described below.

       /proc/sys/kernel/acct
              This  file contains three numbers: highwater, lowwater, and fre-
              quency.  If BSD-style process accounting is enabled, these  val-
              ues control its behavior.  If free space on filesystem where the
              log lives goes below lowwater percent, accounting suspends.   If
              free  space  gets  above  highwater percent, accounting resumes.
              frequency determines how often the kernel checks the  amount  of
              free  space  (value is in seconds).  Default values are 4, 2 and
              30.  That is, suspend accounting if 2% or less  space  is  free;
              resume  it  if  4%  or  more space is free; consider information
              about amount of free space valid for 30 seconds.

       /proc/sys/kernel/auto_msgmni (Linux 2.6.27 to 3.18)
              From Linux 2.6.27 to 3.18, this file was used to control  recom-
              puting of the value in /proc/sys/kernel/msgmni upon the addition
              or removal of memory or  upon  IPC  namespace  creation/removal.
              Echoing  "1" into this file enabled msgmni automatic recomputing
              (and triggered a recomputation of msgmni based  on  the  current
              amount of available memory and number of IPC namespaces).  Echo-
              ing "0" disabled automatic recomputing.  (Automatic  recomputing
              was  also  disabled  if  a  value  was  explicitly  assigned  to
              /proc/sys/kernel/msgmni.)  The default value in auto_msgmni  was
              1.

              Since  Linux  3.19,  the  content  of  this  file  has no effect
              (because msgmni defaults to near the  maximum  value  possible),
              and reads from this file always return the value "0".

       /proc/sys/kernel/cap_last_cap (since Linux 3.2)
              See capabilities(7).

       /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
              This  file holds the value of the kernel capability bounding set
              (expressed as a signed  decimal  number).   This  set  is  ANDed
              against   the   capabilities   permitted  to  a  process  during
              execve(2).  Starting with Linux 2.6.25, the system-wide capabil-
              ity  bounding  set disappeared, and was replaced by a per-thread
              bounding set; see capabilities(7).

       /proc/sys/kernel/core_pattern
              See core(5).

       /proc/sys/kernel/core_uses_pid
              See core(5).

       /proc/sys/kernel/ctrl-alt-del
              This file controls the handling of Ctrl-Alt-Del  from  the  key-
              board.   When  the  value  in  this  file  is 0, Ctrl-Alt-Del is
              trapped and sent to the init(1) program  to  handle  a  graceful
              restart.   When the value is greater than zero, Linux's reaction
              to a Vulcan Nerve Pinch (tm) will be an immediate reboot,  with-
              out  even syncing its dirty buffers.  Note: when a program (like
              dosemu) has the keyboard in  "raw"  mode,  the  ctrl-alt-del  is
              intercepted by the program before it ever reaches the kernel tty
              layer, and it's up to the program to decide what to do with it.

       /proc/sys/kernel/dmesg_restrict (since Linux 2.6.37)
              The value in this file determines who can see kernel syslog con-
              tents.   A  value of 0 in this file imposes no restrictions.  If
              the value is 1, only privileged users can read the  kernel  sys-
              log.   (See  syslog(2) for more details.)  Since Linux 3.4, only
              users with the CAP_SYS_ADMIN capability may change the value  in
              this file.

       /proc/sys/kernel/domainname and /proc/sys/kernel/hostname
              can  be  used  to  set the NIS/YP domainname and the hostname of
              your box in exactly the same way as the  commands  domainname(1)
              and hostname(1), that is:

                  # echo 'darkstar' > /proc/sys/kernel/hostname
                  # echo 'mydomain' > /proc/sys/kernel/domainname

              has the same effect as

                  # hostname 'darkstar'
                  # domainname 'mydomain'

              Note,  however, that the classic darkstar.frop.org has the host-
              name "darkstar" and DNS (Internet Domain Name Server) domainname
              "frop.org", not to be confused with the NIS (Network Information
              Service) or YP (Yellow  Pages)  domainname.   These  two  domain
              names  are  in general different.  For a detailed discussion see
              the hostname(1) man page.

       /proc/sys/kernel/hotplug
              This file contains the path for the hotplug policy  agent.   The
              default value in this file is /sbin/hotplug.

       /proc/sys/kernel/htab-reclaim
              (PowerPC  only) If this file is set to a nonzero value, the Pow-
              erPC htab (see kernel  file  Documentation/powerpc/ppc_htab.txt)
              is pruned each time the system hits the idle loop.

       /proc/sys/kernel/kptr_restrict (since Linux 2.6.38)
              The  value  in this file determines whether kernel addresses are
              exposed via /proc files and other interfaces.  A value of  0  in
              this  file  imposes  no restrictions.  If the value is 1, kernel
              pointers printed using the %pK format specifier will be replaced
              with  zeros  unless  the user has the CAP_SYSLOG capability.  If
              the value is 2, kernel pointers printed  using  the  %pK  format
              specifier  will  be replaced with zeros regardless of the user's
              capabilities.  The initial default value for this  file  was  1,
              but  the  default was changed to 0 in Linux 2.6.39.  Since Linux
              3.4, only users with the CAP_SYS_ADMIN capability can change the
              value in this file.

       /proc/sys/kernel/l2cr
              (PowerPC  only)  This  file contains a flag that controls the L2
              cache of G3 processor boards.  If  0,  the  cache  is  disabled.
              Enabled if nonzero.

       /proc/sys/kernel/modprobe
              This  file  contains the path for the kernel module loader.  The
              default value is /sbin/modprobe.  The file is  present  only  if
              the  kernel  is  built  with  the CONFIG_MODULES (CONFIG_KMOD in
              Linux 2.6.26 and earlier) option enabled.  It  is  described  by
              the  Linux  kernel  source  file Documentation/kmod.txt (present
              only in kernel 2.4 and earlier).

       /proc/sys/kernel/modules_disabled (since Linux 2.6.31)
              A toggle value indicating if modules are allowed to be loaded in
              an  otherwise  modular kernel.  This toggle defaults to off (0),
              but can be set true (1).  Once  true,  modules  can  be  neither
              loaded nor unloaded, and the toggle cannot be set back to false.
              The file is present only if the kernel is built  with  the  CON-
              FIG_MODULES option enabled.

       /proc/sys/kernel/msgmax (since Linux 2.2)
              This  file  defines  a  system-wide limit specifying the maximum
              number of bytes in a single message written on a System  V  mes-
              sage queue.

       /proc/sys/kernel/msgmni (since Linux 2.4)
              This file defines the system-wide limit on the number of message
              queue identifiers.  See also /proc/sys/kernel/auto_msgmni.

       /proc/sys/kernel/msgmnb (since Linux 2.2)
              This file defines a system-wide parameter used to initialize the
              msg_qbytes setting for subsequently created message queues.  The
              msg_qbytes setting specifies the maximum number  of  bytes  that
              may be written to the message queue.

       /proc/sys/kernel/ngroups_max (since Linux 2.6.4)
              This  is  a  read-only file that displays the upper limit on the
              number of a process's group memberships.

       /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
              These files give substrings of /proc/version.

       /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
              These files duplicate  the  files  /proc/sys/fs/overflowgid  and
              /proc/sys/fs/overflowuid.

       /proc/sys/kernel/panic
              This  file  gives  read/write  access  to  the  kernel  variable
              panic_timeout.  If this is zero,  the  kernel  will  loop  on  a
              panic;  if  nonzero, it indicates that the kernel should autore-
              boot after this number of seconds.  When you  use  the  software
              watchdog device driver, the recommended setting is 60.

       /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
              This  file controls the kernel's behavior when an oops or BUG is
              encountered.  If this file contains 0, then the system tries  to
              continue  operation.  If it contains 1, then the system delays a
              few seconds (to give klogd time to record the oops  output)  and
              then   panics.   If  the  /proc/sys/kernel/panic  file  is  also
              nonzero, then the machine will be rebooted.

       /proc/sys/kernel/pid_max (since Linux 2.5.34)
              This file specifies the value at which PIDs wrap  around  (i.e.,
              the  value  in  this  file is one greater than the maximum PID).
              PIDs greater than this value are not allocated; thus, the  value
              in  this file also acts as a system-wide limit on the total num-
              ber of processes and threads.  The default value for this  file,
              32768,  results in the same range of PIDs as on earlier kernels.
              On 32-bit platforms, 32768 is the maximum value for pid_max.  On
              64-bit  systems,  pid_max  can  be  set  to any value up to 2^22
              (PID_MAX_LIMIT, approximately 4 million).

       /proc/sys/kernel/powersave-nap (PowerPC only)
              This file contains a flag.  If set, Linux-PPC will use the "nap"
              mode of powersaving, otherwise the "doze" mode will be used.

       /proc/sys/kernel/printk
              See syslog(2).

       /proc/sys/kernel/pty (since Linux 2.6.4)
              This directory contains two files relating to the number of UNIX
              98 pseudoterminals (see pts(4)) on the system.

       /proc/sys/kernel/pty/max
              This file defines the maximum number of pseudoterminals.

       /proc/sys/kernel/pty/nr
              This read-only file indicates how many pseudoterminals are  cur-
              rently in use.

       /proc/sys/kernel/random
              This directory contains various parameters controlling the oper-
              ation of the file /dev/random.  See random(4) for further infor-
              mation.

       /proc/sys/kernel/random/uuid (since Linux 2.4)
              Each  read from this read-only file returns a randomly generated
              128-bit UUID, as a string in the standard UUID format.

       /proc/sys/kernel/randomize_va_space (since Linux 2.6.12)
              Select the address space layout randomization (ASLR) policy  for
              the  system  (on architectures that support ASLR).  Three values
              are supported for this file:

              0  Turn ASLR off.  This is the default  for  architectures  that
                 don't  support  ASLR,  and when the kernel is booted with the
                 norandmaps parameter.

              1  Make the addresses of mmap(2) allocations, the stack, and the
                 VDSO  page  randomized.   Among other things, this means that
                 shared libraries will be loaded at randomized addresses.  The
                 text  segment of PIE-linked binaries will also be loaded at a
                 randomized address.  This value is the default if the  kernel
                 was configured with CONFIG_COMPAT_BRK.

              2  (Since  Linux  2.6.25) Also support heap randomization.  This
                 value is the default if the kernel was  not  configured  with
                 CONFIG_COMPAT_BRK.

       /proc/sys/kernel/real-root-dev
              This file is documented in the Linux kernel source file Documen-
              tation/initrd.txt.

       /proc/sys/kernel/reboot-cmd (Sparc only)
              This file seems to be a way to give an  argument  to  the  SPARC
              ROM/Flash  boot  loader.   Maybe  to  tell  it  what to do after
              rebooting?

       /proc/sys/kernel/rtsig-max
              (Only in kernels up to and including  2.6.7;  see  setrlimit(2))
              This  file can be used to tune the maximum number of POSIX real-
              time (queued) signals that can be outstanding in the system.

       /proc/sys/kernel/rtsig-nr
              (Only in kernels up to and including 2.6.7.)   This  file  shows
              the number POSIX real-time signals currently queued.

       /proc/sys/kernel/sched_rr_timeslice_ms (since Linux 3.9)
              See sched_rr_get_interval(2).

       /proc/sys/kernel/sched_rt_period_us (Since Linux 2.6.25)
              See sched(7).

       /proc/sys/kernel/sched_rt_runtime_us (Since Linux 2.6.25)
              See sched(7).

       /proc/sys/kernel/sem (since Linux 2.4)
              This  file  contains  4 numbers defining limits for System V IPC
              semaphores.  These fields are, in order:

              SEMMSL  The maximum semaphores per semaphore set.

              SEMMNS  A system-wide limit on the number of semaphores  in  all
                      semaphore sets.

              SEMOPM  The  maximum  number of operations that may be specified
                      in a semop(2) call.

              SEMMNI  A system-wide limit on the maximum number  of  semaphore
                      identifiers.

       /proc/sys/kernel/sg-big-buff
              This file shows the size of the generic SCSI device (sg) buffer.
              You can't tune it just yet, but you could change it  at  compile
              time  by  editing  include/scsi/sg.h  and  changing the value of
              SG_BIG_BUFF.  However, there shouldn't be any reason  to  change
              this value.

       /proc/sys/kernel/shm_rmid_forced (since Linux 3.1)
              If  this  file  is set to 1, all System V shared memory segments
              will be marked for destruction as soon as the number of attached
              processes  falls to zero; in other words, it is no longer possi-
              ble to create shared memory segments that exist independently of
              any attached process.

              The effect is as though a shmctl(2) IPC_RMID is performed on all
              existing segments as well as all segments created in the  future
              (until  this  file  is reset to 0).  Note that existing segments
              that are attached to no process will  be  immediately  destroyed
              when  this  file  is  set  to  1.  Setting this option will also
              destroy segments that were created,  but  never  attached,  upon
              termination  of  the  process  that  created  the  segment  with
              shmget(2).

              Setting this file to 1 provides a way of ensuring that all  Sys-
              tem  V  shared  memory segments are counted against the resource
              usage and resource limits (see the description of  RLIMIT_AS  in
              getrlimit(2)) of at least one process.

              Because  setting  this  file to 1 produces behavior that is non-
              standard and could also break existing applications, the default
              value  in this file is 0.  Only set this file to 1 if you have a
              good understanding of the semantics of  the  applications  using
              System V shared memory on your system.

       /proc/sys/kernel/shmall (since Linux 2.2)
              This  file contains the system-wide limit on the total number of
              pages of System V shared memory.

       /proc/sys/kernel/shmmax (since Linux 2.2)
              This file can be used to query and set the run-time limit on the
              maximum  (System  V  IPC) shared memory segment size that can be
              created.  Shared memory segments up to 1GB are now supported  in
              the kernel.  This value defaults to SHMMAX.

       /proc/sys/kernel/shmmni (since Linux 2.4)
              This  file  specifies the system-wide maximum number of System V
              shared memory segments that can be created.

       /proc/sys/kernel/sysctl_writes_strict (since Linux 3.16)
              The value in this file determines how the  file  offset  affects
              the  behavior of updating entries in files under /proc/sys.  The
              file has three possible values:

              -1  This provides legacy  handling,  with  no  printk  warnings.
                  Each  write(2)  must  fully contain the value to be written,
                  and multiple writes on the same file descriptor  will  over-
                  write the entire value, regardless of the file position.

              0   (default)  This  provides  the  same behavior as for -1, but
                  printk warnings  are  written  for  processes  that  perform
                  writes when the file offset is not 0.

              1   Respect  the file offset when writing strings into /proc/sys
                  files.  Multiple writes will append  to  the  value  buffer.
                  Anything written beyond the maximum length of the value buf-
                  fer will be ignored.  Writes to  numeric  /proc/sys  entries
                  must  always be at file offset 0 and the value must be fully
                  contained in the buffer provided to write(2).

       /proc/sys/kernel/sysrq
              This file controls the functions allowed to be  invoked  by  the
              SysRq  key.   By default, the file contains 1 meaning that every
              possible SysRq request is allowed  (in  older  kernel  versions,
              SysRq was disabled by default, and you were required to specifi-
              cally enable it at run-time, but this is not the case any more).
              Possible values in this file are:

              0    Disable sysrq completely

              1    Enable all functions of sysrq

              > 1  Bit mask of allowed sysrq functions, as follows:
                     2  Enable control of console logging level
                     4  Enable control of keyboard (SAK, unraw)
                     8  Enable debugging dumps of processes etc.
                    16  Enable sync command
                    32  Enable remount read-only
                    64  Enable signaling of processes (term, kill, oom-kill)
                   128  Allow reboot/poweroff
                   256  Allow nicing of all real-time tasks

              This  file is present only if the CONFIG_MAGIC_SYSRQ kernel con-
              figuration option is enabled.  For further details see the Linux
              kernel source file Documentation/sysrq.txt.

       /proc/sys/kernel/version
              This file contains a string such as:

                  #5 Wed Feb 25 21:49:24 MET 1998

              The  "#5"  means  that  this is the fifth kernel built from this
              source base and the date following it  indicates  the  time  the
              kernel was built.

       /proc/sys/kernel/threads-max (since Linux 2.3.11)
              This  file  specifies  the  system-wide  limit  on the number of
              threads (tasks) that can be created on the system.

              Since Linux 4.1, the value that can be written to threads-max is
              bounded.  The minimum value that can be written is 20.  The max-
              imum value  that  can  be  written  is  given  by  the  constant
              FUTEX_TID_MASK  (0x3fffffff).   If a value outside of this range
              is written to threads-max, the error EINVAL occurs.

              The value written is checked against the  available  RAM  pages.
              If the thread structures would occupy too much (more than 1/8th)
              of the available RAM pages, threads-max is reduced accordingly.

       /proc/sys/kernel/yama/ptrace_scope (since Linux 3.5)
              See ptrace(2).

       /proc/sys/kernel/zero-paged (PowerPC only)
              This file contains a flag.  When  enabled  (nonzero),  Linux-PPC
              will  pre-zero  pages  in  the  idle  loop, possibly speeding up
              get_free_pages.

       /proc/sys/net
              This directory contains networking stuff.  Explanations for some
              of  the  files  under  this directory can be found in tcp(7) and
              ip(7).

       /proc/sys/net/core/bpf_jit_enable
              See bpf(2).

       /proc/sys/net/core/somaxconn
              This file defines a ceiling value for the  backlog  argument  of
              listen(2); see the listen(2) manual page for details.

       /proc/sys/proc
              This directory may be empty.

       /proc/sys/sunrpc
              This  directory  supports  Sun remote procedure call for network
              filesystem (NFS).  On some systems, it is not present.

       /proc/sys/vm
              This directory contains files for memory management tuning, buf-
              fer and cache management.

       /proc/sys/vm/compact_memory (since Linux 2.6.35)
              When  1  is  written  to this file, all zones are compacted such
              that free memory is available in contiguous blocks where  possi-
              ble.   The  effect  of  this  action  can  be  seen by examining
              /proc/buddyinfo.

              Only present if  the  kernel  was  configured  with  CONFIG_COM-
              PACTION.

       /proc/sys/vm/drop_caches (since Linux 2.6.16)
              Writing  to  this  file  causes the kernel to drop clean caches,
              dentries, and inodes from memory, causing that memory to  become
              free.  This can be useful for memory management testing and per-
              forming reproducible filesystem benchmarks.  Because writing  to
              this  file  causes  the  benefits  of caching to be lost, it can
              degrade overall system performance.

              To free pagecache, use:

                  echo 1 > /proc/sys/vm/drop_caches

              To free dentries and inodes, use:

                  echo 2 > /proc/sys/vm/drop_caches

              To free pagecache, dentries and inodes, use:

                  echo 3 > /proc/sys/vm/drop_caches

              Because writing to this file is a nondestructive  operation  and
              dirty  objects  are  not  freeable,  the user should run sync(1)
              first.

       /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
              If nonzero, this disables the new 32-bit memory-mapping  layout;
              the kernel will use the legacy (2.4) layout for all processes.

       /proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)
              Control  how  to kill processes when an uncorrected memory error
              (typically a 2-bit error in a memory module) that cannot be han-
              dled  by  the  kernel is detected in the background by hardware.
              In some cases (like the page still having a valid copy on disk),
              the kernel will handle the failure transparently without affect-
              ing any applications.  But if there is no other up-to-date  copy
              of  the data, it will kill processes to prevent any data corrup-
              tions from propagating.

              The file has one of the following values:

              1:  Kill all processes that have  the  corrupted-and-not-reload-
                  able  page  mapped  as  soon  as the corruption is detected.
                  Note this is not supported for a few types  of  pages,  like
                  kernel  internally  allocated  data  or  the swap cache, but
                  works for the majority of user pages.

              0:  Only unmap the corrupted page from all  processes  and  kill
                  only a process that tries to access it.

              The  kill is performed using a SIGBUS signal with si_code set to
              BUS_MCEERR_AO.  Processes can handle this if they want  to;  see
              sigaction(2) for more details.

              This  feature  is  active  only  on architectures/platforms with
              advanced machine check handling  and  depends  on  the  hardware
              capabilities.

              Applications  can override the memory_failure_early_kill setting
              individually with the prctl(2) PR_MCE_KILL operation.

              Only present if  the  kernel  was  configured  with  CONFIG_MEM-
              ORY_FAILURE.

       /proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)
              Enable memory failure recovery (when supported by the platform)

              1:  Attempt recovery.

              0:  Always panic on a memory failure.

              Only  present  if  the  kernel  was  configured with CONFIG_MEM-
              ORY_FAILURE.

       /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
              Enables a system-wide task dump (excluding kernel threads) to be
              produced  when  the  kernel  performs  an OOM-killing.  The dump
              includes  the  following  information  for  each  task  (thread,
              process): thread ID, real user ID, thread group ID (process ID),
              virtual memory size, resident set size, the CPU that the task is
              scheduled   on,   oom_adj   score   (see   the   description  of
              /proc/[pid]/oom_adj), and command  name.   This  is  helpful  to
              determine  why  the  OOM-killer  was invoked and to identify the
              rogue task that caused it.

              If this contains the value zero, this information is suppressed.
              On  very  large  systems  with thousands of tasks, it may not be
              feasible to dump the memory  state  information  for  each  one.
              Such systems should not be forced to incur a performance penalty
              in OOM situations when the information may not be desired.

              If this is set to nonzero, this information  is  shown  whenever
              the OOM-killer actually kills a memory-hogging task.

              The default value is 0.

       /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
              This enables or disables killing the OOM-triggering task in out-
              of-memory situations.

              If this is set to zero, the OOM-killer  will  scan  through  the
              entire  tasklist  and select a task based on heuristics to kill.
              This normally selects a rogue memory-hogging task that frees  up
              a large amount of memory when killed.

              If  this is set to nonzero, the OOM-killer simply kills the task
              that triggered the out-of-memory condition.  This avoids a  pos-
              sibly expensive tasklist scan.

              If  /proc/sys/vm/panic_on_oom  is  nonzero,  it takes precedence
              over whatever value is  used  in  /proc/sys/vm/oom_kill_allocat-
              ing_task.

              The default value is 0.

       /proc/sys/vm/overcommit_kbytes (since Linux 3.14)
              This writable file provides an alternative to /proc/sys/vm/over-
              commit_ratio    for    controlling    the    CommitLimit    when
              /proc/sys/vm/overcommit_memory  has  the value 2.  It allows the
              amount of memory overcommitting to be specified as  an  absolute
              value  (in  kB),  rather  than  as a percentage, as is done with
              overcommit_ratio.  This allows for finer-grained control of Com-
              mitLimit on systems with extremely large memory sizes.

              Only  one  of  overcommit_kbytes or overcommit_ratio can have an
              effect: if overcommit_kbytes has a nonzero  value,  then  it  is
              used  to  calculate  CommitLimit,  otherwise overcommit_ratio is
              used.  Writing a value to either of these files causes the value
              in the other file to be set to zero.

       /proc/sys/vm/overcommit_memory
              This  file  contains  the kernel virtual memory accounting mode.
              Values are:

                     0: heuristic overcommit (this is the default)
                     1: always overcommit, never check
                     2: always check, never overcommit

              In mode 0, calls of mmap(2) with MAP_NORESERVE are not  checked,
              and  the default check is very weak, leading to the risk of get-
              ting a process "OOM-killed".  Under Linux 2.4, any nonzero value
              implies mode 1.

              In mode 2 (available since Linux 2.6), the total virtual address
              space that can be allocated (CommitLimit  in  /proc/meminfo)  is
              calculated as

                  CommitLimit = (total_RAM - total_huge_TLB) *
                                overcommit_ratio / 100 + total_swap

              where:

                   *  total_RAM is the total amount of RAM on the system;

                   *  total_huge_TLB  is  the  amount  of memory set aside for
                      huge pages;

                   *  overcommit_ratio is the value  in  /proc/sys/vm/overcom-
                      mit_ratio; and

                   *  total_swap is the amount of swap space.

              For  example,  on  a  system  with 16GB of physical RAM, 16GB of
              swap, no space dedicated to huge pages, and an  overcommit_ratio
              of 50, this formula yields a CommitLimit of 24GB.

              Since Linux 3.14, if the value in /proc/sys/vm/overcommit_kbytes
              is nonzero, then CommitLimit is instead calculated as:

                  CommitLimit = overcommit_kbytes + total_swap

       /proc/sys/vm/overcommit_ratio (since Linux 2.6.0)
              This writable file defines a percentage by which memory  can  be
              overcommitted.   The  default  value in the file is 50.  See the
              description of /proc/sys/vm/overcommit_memory.

       /proc/sys/vm/panic_on_oom (since Linux 2.6.18)
              This enables or disables a kernel panic in an out-of-memory sit-
              uation.

              If this file is set to the value 0, the kernel's OOM-killer will
              kill some rogue process.  Usually, the  OOM-killer  is  able  to
              kill a rogue process and the system will survive.

              If  this  file  is  set to the value 1, then the kernel normally
              panics when out-of-memory happens.  However, if a process limits
              allocations  to  certain  nodes  using memory policies (mbind(2)
              MPOL_BIND) or cpusets (cpuset(7)) and those nodes  reach  memory
              exhaustion  status, one process may be killed by the OOM-killer.
              No panic occurs in this case: because other nodes' memory may be
              free,  this  means the system as a whole may not have reached an
              out-of-memory situation yet.

              If this file is set to the value 2,  the  kernel  always  panics
              when an out-of-memory condition occurs.

              The default value is 0.  1 and 2 are for failover of clustering.
              Select either according to your policy of failover.

       /proc/sys/vm/swappiness
              The value in this file controls how aggressively the kernel will
              swap memory pages.  Higher values increase aggressiveness, lower
              values decrease aggressiveness.  The default value is 60.

       /proc/sysrq-trigger (since Linux 2.4.21)
              Writing a character to this file triggers the same  SysRq  func-
              tion  as  typing  ALT-SysRq-<character>  (see the description of
              /proc/sys/kernel/sysrq).  This file is normally writable only by
              root.  For further details see the Linux kernel source file Doc-
              umentation/sysrq.txt.

       /proc/sysvipc
              Subdirectory containing  the  pseudo-files  msg,  sem  and  shm.
              These  files  list the System V Interprocess Communication (IPC)
              objects (respectively: message queues,  semaphores,  and  shared
              memory)  that  currently  exist on the system, providing similar
              information to that available via  ipcs(1).   These  files  have
              headers  and  are  formatted  (one IPC object per line) for easy
              understanding.  svipc(7)  provides  further  background  on  the
              information shown by these files.

       /proc/thread-self (since Linux 3.17)
              This directory refers to the thread accessing the /proc filesys-
              tem, and is identical  to  the  /proc/self/task/[tid]  directory
              named by the process thread ID ([tid]) of the same thread.

       /proc/timer_list (since Linux 2.6.21)
              This  read-only  file  exposes  a  list of all currently pending
              (high-resolution) timers, all  clock-event  sources,  and  their
              parameters in a human-readable form.

       /proc/timer_stats (since Linux 2.6.21)
              This  is  a  debugging facility to make timer (ab)use in a Linux
              system visible to kernel and user-space developers.  It  can  be
              used  by  kernel  and user-space developers to verify that their
              code does not make undue use of timers.  The goal  is  to  avoid
              unnecessary wakeups, thereby optimizing power consumption.

              If  enabled in the kernel (CONFIG_TIMER_STATS), but not used, it
              has almost zero runtime overhead and a  relatively  small  data-
              structure  overhead.   Even if collection is enabled at runtime,
              overhead is low: all  the  locking  is  per-CPU  and  lookup  is
              hashed.

              The  /proc/timer_stats  file  is  used  both to control sampling
              facility and to read out the sampled information.

              The timer_stats functionality is inactive on bootup.  A sampling
              period can be started using the following command:

                  # echo 1 > /proc/timer_stats

              The following command stops a sampling period:

                  # echo 0 > /proc/timer_stats

              The statistics can be retrieved by:

                  $ cat /proc/timer_stats

              While  sampling  is enabled, each readout from /proc/timer_stats
              will see newly updated statistics.  Once sampling  is  disabled,
              the  sampled  information  is  kept until a new sample period is
              started.  This allows multiple readouts.

              Sample output from /proc/timer_stats:

   $ cat /proc/timer_stats
   Timer Stats Version: v0.3
   Sample period: 1.764 s
   Collection: active
     255,     0 swapper/3        hrtimer_start_range_ns (tick_sched_timer)
      71,     0 swapper/1        hrtimer_start_range_ns (tick_sched_timer)
      58,     0 swapper/0        hrtimer_start_range_ns (tick_sched_timer)
       4,  1694 gnome-shell      mod_delayed_work_on (delayed_work_timer_fn)
      17,     7 rcu_sched        rcu_gp_kthread (process_timeout)
   ...
       1,  4911 kworker/u16:0    mod_delayed_work_on (delayed_work_timer_fn)
      1D,  2522 kworker/0:0      queue_delayed_work_on (delayed_work_timer_fn)
   1029 total events, 583.333 events/sec

              The output columns are:

              *  a count of the number  of  events,  optionally  (since  Linux
                 2.6.23)  followed  by  the letter 'D' if this is a deferrable
                 timer;

              *  the PID of the process that initialized the timer;

              *  the name of the process that initialized the timer;

              *  the function where the timer was initialized; and

              *  (in parentheses) the callback  function  that  is  associated
                 with the timer.

       /proc/tty
              Subdirectory  containing the pseudo-files and subdirectories for
              tty drivers and line disciplines.

       /proc/uptime
              This file contains two numbers: the uptime of the  system  (sec-
              onds), and the amount of time spent in idle process (seconds).

       /proc/version
              This string identifies the kernel version that is currently run-
              ning.  It  includes  the  contents  of  /proc/sys/kernel/ostype,
              /proc/sys/kernel/osrelease  and  /proc/sys/kernel/version.   For
              example:
            Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994

       /proc/vmstat (since Linux 2.6.0)
              This file displays various virtual memory statistics.  Each line
              of  this  file  contains  a single name-value pair, delimited by
              white space.  Some files are present only if the kernel was con-
              figured  with  suitable  options.   (In  some cases, the options
              required for particular files have changed  across  kernel  ver-
              sions,  so  they  are  not listed here.  Details can be found by
              consulting the kernel source code.)  The following fields may be
              present:

              nr_free_pages (since Linux 2.6.31)

              nr_alloc_batch (since Linux 3.12)

              nr_inactive_anon (since Linux 2.6.28)

              nr_active_anon (since Linux 2.6.28)

              nr_inactive_file (since Linux 2.6.28)

              nr_active_file (since Linux 2.6.28)

              nr_unevictable (since Linux 2.6.28)

              nr_mlock (since Linux 2.6.28)

              nr_anon_pages (since Linux 2.6.18)

              nr_mapped (since Linux 2.6.0)

              nr_file_pages (since Linux 2.6.18)

              nr_dirty (since Linux 2.6.0)

              nr_writeback (since Linux 2.6.0)

              nr_slab_reclaimable (since Linux 2.6.19)

              nr_slab_unreclaimable (since Linux 2.6.19)

              nr_page_table_pages (since Linux 2.6.0)

              nr_kernel_stack (since Linux 2.6.32)
                     Amount of memory allocated to kernel stacks.

              nr_unstable (since Linux 2.6.0)

              nr_bounce (since Linux 2.6.12)

              nr_vmscan_write (since Linux 2.6.19)

              nr_vmscan_immediate_reclaim (since Linux 3.2)

              nr_writeback_temp (since Linux 2.6.26)

              nr_isolated_anon (since Linux 2.6.32)

              nr_isolated_file (since Linux 2.6.32)

              nr_shmem (since Linux 2.6.32)
                     Pages used by shmem and tmpfs.

              nr_dirtied (since Linux 2.6.37)

              nr_written (since Linux 2.6.37)

              nr_pages_scanned (since Linux 3.17)

              numa_hit (since Linux 2.6.18)

              numa_miss (since Linux 2.6.18)

              numa_foreign (since Linux 2.6.18)

              numa_interleave (since Linux 2.6.18)

              numa_local (since Linux 2.6.18)

              numa_other (since Linux 2.6.18)

              workingset_refault (since Linux 3.15)

              workingset_activate (since Linux 3.15)

              workingset_nodereclaim (since Linux 3.15)

              nr_anon_transparent_hugepages (since Linux 2.6.38)

              nr_free_cma (since Linux 3.7)
                     Number of free CMA (Contiguous Memory Allocator) pages.

              nr_dirty_threshold (since Linux 2.6.37)

              nr_dirty_background_threshold (since Linux 2.6.37)

              pgpgin (since Linux 2.6.0)

              pgpgout (since Linux 2.6.0)

              pswpin (since Linux 2.6.0)

              pswpout (since Linux 2.6.0)

              pgalloc_dma (since Linux 2.6.5)

              pgalloc_dma32 (since Linux 2.6.16)

              pgalloc_normal (since Linux 2.6.5)

              pgalloc_high (since Linux 2.6.5)

              pgalloc_movable (since Linux 2.6.23)

              pgfree (since Linux 2.6.0)

              pgactivate (since Linux 2.6.0)

              pgdeactivate (since Linux 2.6.0)

              pgfault (since Linux 2.6.0)

              pgmajfault (since Linux 2.6.0)

              pgrefill_dma (since Linux 2.6.5)

              pgrefill_dma32 (since Linux 2.6.16)

              pgrefill_normal (since Linux 2.6.5)

              pgrefill_high (since Linux 2.6.5)

              pgrefill_movable (since Linux 2.6.23)

              pgsteal_kswapd_dma (since Linux 3.4)

              pgsteal_kswapd_dma32 (since Linux 3.4)

              pgsteal_kswapd_normal (since Linux 3.4)

              pgsteal_kswapd_high (since Linux 3.4)

              pgsteal_kswapd_movable (since Linux 3.4)

              pgsteal_direct_dma

              pgsteal_direct_dma32 (since Linux 3.4)

              pgsteal_direct_normal (since Linux 3.4)

              pgsteal_direct_high (since Linux 3.4)

              pgsteal_direct_movable (since Linux 2.6.23)

              pgscan_kswapd_dma

              pgscan_kswapd_dma32 (since Linux 2.6.16)

              pgscan_kswapd_normal (since Linux 2.6.5)

              pgscan_kswapd_high

              pgscan_kswapd_movable (since Linux 2.6.23)

              pgscan_direct_dma

              pgscan_direct_dma32 (since Linux 2.6.16)

              pgscan_direct_normal

              pgscan_direct_high

              pgscan_direct_movable (since Linux 2.6.23)

              pgscan_direct_throttle (since Linux 3.6)

              zone_reclaim_failed (since linux 2.6.31)

              pginodesteal (since linux 2.6.0)

              slabs_scanned (since linux 2.6.5)

              kswapd_inodesteal (since linux 2.6.0)

              kswapd_low_wmark_hit_quickly (since 2.6.33)

              kswapd_high_wmark_hit_quickly (since 2.6.33)

              pageoutrun (since Linux 2.6.0)

              allocstall (since Linux 2.6.0)

              pgrotated (since Linux 2.6.0)

              drop_pagecache (since Linux 3.15)

              drop_slab (since Linux 3.15)

              numa_pte_updates (since Linux 3.8)

              numa_huge_pte_updates (since Linux 3.13)

              numa_hint_faults (since Linux 3.8)

              numa_hint_faults_local (since Linux 3.8)

              numa_pages_migrated (since Linux 3.8)

              pgmigrate_success (since Linux 3.8)

              pgmigrate_fail (since Linux 3.8)

              compact_migrate_scanned (since Linux 3.8)

              compact_free_scanned (since Linux 3.8)

              compact_isolated (since Linux 3.8)

              compact_stall (since Linux 2.6.35)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              compact_fail (since Linux 2.6.35)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              compact_success (since Linux 2.6.35)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              htlb_buddy_alloc_success (since Linux 2.6.26)

              htlb_buddy_alloc_fail (since Linux 2.6.26)

              unevictable_pgs_culled (since Linux 2.6.28)

              unevictable_pgs_scanned (since Linux 2.6.28)

              unevictable_pgs_rescued (since Linux 2.6.28)

              unevictable_pgs_mlocked (since Linux 2.6.28)

              unevictable_pgs_munlocked (since Linux 2.6.28)

              unevictable_pgs_cleared (since Linux 2.6.28)

              unevictable_pgs_stranded (since Linux 2.6.28)

              thp_fault_alloc (since Linux 2.6.39)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              thp_fault_fallback (since Linux 2.6.39)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              thp_collapse_alloc (since Linux 2.6.39)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              thp_collapse_alloc_failed (since Linux 2.6.39)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              thp_split (since Linux 2.6.39)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              thp_zero_page_alloc (since Linux 3.8)
                     See   the   kernel   source  file  Documentation/vm/tran-
                     shuge.txt.

              thp_zero_page_alloc_failed (since Linux 3.8)
                     See  the  kernel   source   file   Documentation/vm/tran-
                     shuge.txt.

              balloon_inflate (since Linux 3.18)

              balloon_deflate (since Linux 3.18)

              balloon_migrate (since Linux 3.18)

              nr_tlb_remote_flush (since Linux 3.12)

              nr_tlb_remote_flush_received (since Linux 3.12)

              nr_tlb_local_flush_all (since Linux 3.12)

              nr_tlb_local_flush_one (since Linux 3.12)

              vmacache_find_calls (since Linux 3.16)

              vmacache_find_hits (since Linux 3.16)

              vmacache_full_flushes (since Linux 3.19)

       /proc/zoneinfo (since Linux 2.6.13)
              This  file display information about memory zones.  This is use-
              ful for analyzing virtual memory behavior.

NOTES
       Many strings (i.e., the environment and command line) are in the inter-
       nal  format, with subfields terminated by null bytes ('\0'), so you may
       find that things are more readable if you use od -c or tr  "\000"  "\n"
       to read them.  Alternatively, echo `cat <file>` works well.

       This manual page is incomplete, possibly inaccurate, and is the kind of
       thing that needs to be updated very often.

SEE ALSO
       cat(1), dmesg(1), find(1), free(1), ps(1), tr(1), uptime(1), chroot(2),
       mmap(2),  readlink(2),  syslog(2), slabinfo(5), hier(7), namespaces(7),
       time(7), arp(8), hdparm(8), ifconfig(8), init(1),  lsmod(8),  lspci(8),
       mount(8), netstat(8), procinfo(8), route(8), sysctl(8)

       The Linux kernel source files: Documentation/filesystems/proc.txt Docu-
       mentation/sysctl/fs.txt,  Documentation/sysctl/kernel.txt,   Documenta-
       tion/sysctl/net.txt, and Documentation/sysctl/vm.txt.

COLOPHON
       This  page  is  part of release 4.04 of the Linux man-pages project.  A
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       http://www.kernel.org/doc/man-pages/.

Linux                             2015-12-05                           PROC(5)