FDISK(8)                     System Administration                    FDISK(8)
NAME
       fdisk - manipulate disk partition table

SYNOPSIS
       fdisk [options] device

       fdisk -l [device...]

DESCRIPTION
       fdisk  is a dialog-driven program for creation and manipulation of par-
       tition tables.  It understands GPT, MBR, Sun,  SGI  and  BSD  partition
       tables.

       Block devices can be divided into one or more logical disks called par-
       titions.  This division is recorded in  the  partition  table,  usually
       found in sector 0 of the disk.  (In the BSD world one talks about `disk
       slices' and a `disklabel'.)

       All partitioning is driven by  device  I/O  limits  (the  topology)  by
       default.   fdisk  is  able  to optimize the disk layout for a 4K-sector
       size and use an alignment offset on modern devices for MBR and GPT.  It
       is  always a good idea to follow fdisk's defaults as the default values
       (e.g. first and last partition sectors) and partition  sizes  specified
       by  the  +<size>{M,G,...}  notation are always aligned according to the
       device properties.

       Note that partx(8) provides a rich interface for scripts to print  disk
       layouts,  fdisk  is mostly designed for humans.  Backward compatibility
       in the output of fdisk is not guaranteed.   The  input  (the  commands)
       should always be backward compatible.

OPTIONS
       -b, --sector-size sectorsize
              Specify  the  sector  size  of  the disk.  Valid values are 512,
              1024, 2048, and 4096.  (Recent kernels  know  the  sector  size.
              Use  this option only on old kernels or to override the kernel's
              ideas.)  Since  util-linux-2.17,  fdisk  differentiates  between
              logical and physical sector size.  This option changes both sec-
              tor sizes to sectorsize.

       -B, --protect-boot
              Don't erase the begin of the first disk sector when create a new
              disk label. This feature is supported for GPT and MBR.

       -c, --compatibility[=mode]
              Specify  the compatibility mode, 'dos' or 'nondos'.  The default
              is non-DOS mode.  For backward compatibility, it is possible  to
              use  the option without the mode argument -- then the default is
              used.  Note that the optional mode argument cannot be  separated
              from  the  -c option by a space, the correct form is for example
              '-c=dos'.

       -h, --help
              Display a help text and exit.

       -L, --color[=when]
              Colorize the output.  The optional argument when  can  be  auto,
              never  or  always.  If the when argument is omitted, it defaults
              to auto.  The colors can be disabled, for the  current  built-in
              default see --help output. See also the COLORS section.

       -l, --list
              List  the  partition  tables  for the specified devices and then
              exit.  If no devices are given, those mentioned in  /proc/parti-
              tions (if that file exists) are used.

       -o, --output list
              Specify which output columns to print.  Use --help to get a list
              of all supported columns.

              The default list of columns may be extended if list is specified
              in the format +list (e.g. -o +UUID).

       -s, --getsz
              Print  the  size in 512-byte sectors of each given block device.
              This option is DEPRECATED in favour of blockdev(1).

       -t, --type type
              Enable support only for disklabels of the  specified  type,  and
              disable support for all other types.

       -u, --units[=unit]
              When  listing  partition  tables,  show sizes in 'sectors' or in
              'cylinders'.  The default is to  show  sizes  in  sectors.   For
              backward compatibility, it is possible to use the option without
              the unit argument -- then the default is used.   Note  that  the
              optional unit argument cannot be separated from the -u option by
              a space, the correct form is for example '-u=cylinders'.

       -C, --cylinders number
              Specify the number of cylinders of the disk.  I have no idea why
              anybody would want to do so.

       -H, --heads number
              Specify the number of heads of the disk.  (Not the physical num-
              ber, of course, but the number used for partition tables.)  Rea-
              sonable values are 255 and 16.

       -S, --sectors number
              Specify  the  number of sectors per track of the disk.  (Not the
              physical number, of course, but the number  used  for  partition
              tables.) A reasonable value is 63.

       -V, --version
              Display version information and exit.

DEVICES
       The  device  is usually /dev/sda, /dev/sdb or so.  A device name refers
       to the entire disk.  Old systems without libata (a library used  inside
       the  Linux  kernel  to support ATA host controllers and devices) make a
       difference between IDE and SCSI disks.  In such cases the  device  name
       will be /dev/hd* (IDE) or /dev/sd* (SCSI).

       The  partition  is  a  device name followed by a partition number.  For
       example, /dev/sda1 is the first partition on the first hard disk in the
       system.    See   also   Linux   kernel  documentation  (the  Documenta-
       tion/devices.txt file).

SIZES
       The "last sector" dialog accepts partition size specified by number  of
       sectors or by +<size>{K,B,M,G,...} notation.

       If  the  size is prefixed by  '+' then it is interpreted as relative to
       the partition first sector. In this case the size is expected in  bytes
       and the number may be followed by the multiplicative suffixes KiB=1024,
       MiB=1024*1024, and so on for GiB, TiB, PiB, EiB, ZiB and YiB. The  "iB"
       is optional, e.g. "K" has the same meaning as "KiB".

       The  relative  sizes are always aligned according to device I/O limits.
       The +<size>{K,B,M,G,...} notation is recommended.

       For backward compatibility fdisk also  accepts  the  suffixes  KB=1000,
       MB=1000*1000,  and so on for GB, TB, PB, EB, ZB and YB. These 10^N suf-
       fixes are deprecated.

SCRIPT FILES
       fdisk allows to read (by 'I' command) sfdisk compatible  script  files.
       The script is applied to in-memory partition table, and then it is pos-
       sible to modify the partition table before you write it to the device.

       And vice-versa it is possible to write the current in-memory disk  lay-
       out to the script file by command 'O'.

       The  script  files  are  compatible  between  cfdisk, sfdisk, fdisk and
       another libfdisk applications. For more details see sfdisk(8).

DISK LABELS
       GPT (GUID Partition Table)
              GPT is modern standard for the layout of  the  partition  table.
              GPT  uses  64-bit  logical block addresses, checksums, UUIDs and
              names for partitions  and  an  unlimited  number  of  partitions
              (although  the number of partitions is usually restricted to 128
              in many partitioning tools).

              Note that the first sector is still reserved  for  a  protective
              MBR in the GPT specification.  It prevents MBR-only partitioning
              tools from mis-recognizing and overwriting GPT disks.

              GPT is always a better choice than  MBR,  especially  on  modern
              hardware with a UEFI boot loader.

       DOS-type (MBR)
              A  DOS-type  partition table can describe an unlimited number of
              partitions.  In sector 0 there is room for the description of  4
              partitions  (called `primary').  One of these may be an extended
              partition; this  is  a  box  holding  logical  partitions,  with
              descriptors  found  in  a linked list of sectors, each preceding
              the corresponding logical partitions.  The four  primary  parti-
              tions,  present or not, get numbers 1-4.  Logical partitions are
              numbered starting from 5.

              In a DOS-type partition table the starting offset and  the  size
              of  each  partition is stored in two ways: as an absolute number
              of sectors (given in 32 bits), and as a  Cylinders/Heads/Sectors
              triple  (given  in  10+8+6  bits).   The  former  is  OK -- with
              512-byte sectors this will work up to 2 TB.  The latter has  two
              problems.  First, these C/H/S fields can be filled only when the
              number of heads and the number of sectors per track  are  known.
              And second, even if we know what these numbers should be, the 24
              bits that are available do not suffice.  DOS  uses  C/H/S  only,
              Windows uses both, Linux never uses C/H/S.  The C/H/S addressing
              is deprecated and may be unsupported in some  later  fdisk  ver-
              sion.

              Please,  read  the  DOS-mode  section if you want DOS-compatible
              partitions.  fdisk does not care about  cylinder  boundaries  by
              default.

       BSD/Sun-type
              A  BSD/Sun  disklabel  can  describe  8 partitions, the third of
              which should be a `whole disk' partition.  Do not start a parti-
              tion that actually uses its first sector (like a swap partition)
              at cylinder 0, since that will destroy the disklabel.  Note that
              a BSD label is usually nested within a DOS partition.

       IRIX/SGI-type
              An  IRIX/SGI  disklabel can describe 16 partitions, the eleventh
              of which should be an entire `volume' partition, while the ninth
              should  be labeled `volume header'.  The volume header will also
              cover the partition table, i.e., it starts  at  block  zero  and
              extends  by default over five cylinders.  The remaining space in
              the volume header may be used by header directory  entries.   No
              partitions  may  overlap  with  the  volume header.  Also do not
              change its type or make some filesystem on it,  since  you  will
              lose  the  partition  table.   Use  this type of label only when
              working with Linux on IRIX/SGI machines or IRIX/SGI disks  under
              Linux.

       A  sync()  and  an ioctl(BLKRRPART) (rereading the partition table from
       disk) are performed before exiting when the partition  table  has  been
       updated.

DOS mode and DOS 6.x WARNING
       Note  that  all this is deprecated. You don't have to care about things
       like geometry and cylinders on modern operating systems. If you  really
       want  DOS-compatible  partitioning then you have to enable DOS mode and
       cylinder units by using the '-c=dos  -u=cylinders'  fdisk  command-line
       options.

       The DOS 6.x FORMAT command looks for some information in the first sec-
       tor of the data area of the partition, and treats this  information  as
       more  reliable than the information in the partition table.  DOS FORMAT
       expects DOS FDISK to clear the first 512 bytes of the data  area  of  a
       partition  whenever a size change occurs.  DOS FORMAT will look at this
       extra information even if the /U flag is given -- we  consider  this  a
       bug in DOS FORMAT and DOS FDISK.

       The  bottom  line is that if you use fdisk or cfdisk to change the size
       of a DOS partition table entry, then you must also use  dd(1)  to  zero
       the first 512 bytes of that partition before using DOS FORMAT to format
       the partition.  For example, if you were using fdisk to make a DOS par-
       tition table entry for /dev/sda1, then (after exiting fdisk and reboot-
       ing Linux so that the partition table information is valid)  you  would
       use  the  command "dd if=/dev/zero of=/dev/sda1 bs=512 count=1" to zero
       the first 512 bytes of the partition.

       fdisk usually obtains the disk geometry  automatically.   This  is  not
       necessarily  the  physical  disk  geometry (indeed, modern disks do not
       really have anything like a physical geometry, certainly not  something
       that  can be described in the simplistic Cylinders/Heads/Sectors form),
       but it is the disk geometry that MS-DOS uses for the partition table.

       Usually all goes well by default, and there are no problems if Linux is
       the  only  system  on  the disk.  However, if the disk has to be shared
       with other operating systems, it is often a good idea to let  an  fdisk
       from  another operating system make at least one partition.  When Linux
       boots it looks at the partition table, and tries to deduce what  (fake)
       geometry is required for good cooperation with other systems.

       Whenever  a  partition  table is printed out in DOS mode, a consistency
       check is performed on the partition table entries.  This check verifies
       that  the  physical and logical start and end points are identical, and
       that each partition starts and ends on a cylinder boundary (except  for
       the first partition).

       Some  versions  of MS-DOS create a first partition which does not begin
       on a cylinder boundary, but on sector 2 of the first cylinder.   Parti-
       tions  beginning in cylinder 1 cannot begin on a cylinder boundary, but
       this is unlikely to cause difficulty  unless  you  have  OS/2  on  your
       machine.

       For  best results, you should always use an OS-specific partition table
       program.  For example, you should make  DOS  partitions  with  the  DOS
       FDISK program and Linux partitions with the Linux fdisk or Linux cfdisk
       programs.

COLORS
       Implicit coloring can be disabled by an empty  file  /etc/terminal-col-
       ors.d/fdisk.disable.

       See terminal-colors.d(5) for more details about colorization configura-
       tion. The logical color names supported by fdisk are:

       header The header of the output tables.

       help-title
              The help section titles.

       warn   The warning messages.

       welcome
              The welcome message.

AUTHORS
       Karel Zak <kzak@redhat.com>
       Davidlohr Bueso <dave@gnu.org>

       The original version was written by Andries E. Brouwer, A. V. Le  Blanc
       and others.

ENVIRONMENT
       FDISK_DEBUG=all
              enables fdisk debug output.

       LIBFDISK_DEBUG=all
              enables libfdisk debug output.

       LIBBLKID_DEBUG=all
              enables libblkid debug output.

       LIBSMARTCOLS_DEBUG=all
              enables libsmartcols debug output.

SEE ALSO
       cfdisk(8), sfdisk(8), mkfs(8), partx(8)

AVAILABILITY
       The  fdisk  command  is part of the util-linux package and is available
       from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.

util-linux                      September 2013                        FDISK(8)