LOSETUP(8)                   System Administration                  LOSETUP(8)
NAME
       losetup - set up and control loop devices

SYNOPSIS
       Get info:

            losetup loopdev

            losetup -l [-a]

            losetup -j file [-o offset]

       Detach a loop device:

            losetup -d loopdev...

       Detach all associated loop devices:

            losetup -D

       Print the name of the first unused loop device:

            losetup -f

       Set up a loop device:

            losetup [-o offset] [--sizelimit size]
                    [-Pr] [--show] -f|loopdev file

       Resize a loop device:

            losetup -c loopdev

DESCRIPTION
       losetup  is  used to associate loop devices with regular files or block
       devices, to detach loop devices, and to query  the  status  of  a  loop
       device.   If only the loopdev argument is given, the status of the cor-
       responding loop device is shown.  If  no  option  is  given,  all  loop
       devices are shown.

       Note  that the old output format (i.e. losetup -a) with comma-delimited
       strings is deprecated in favour of the --list output format.

OPTIONS
       The size and offset arguments 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")  or  the suffixes KB (=1000), MB (=1000*1000), and so on for
       GB, TB, PB, EB, ZB and YB.

       -a, --all
              Show the status of all loop devices.  Note that not all informa-
              tion  is  accessible  for non-root users.  See also --list.  The
              old output format (as printed without --list) is deprecated.

       -c, --set-capacity loopdev
              Force the loop driver to reread the size of the file  associated
              with the specified loop device.

       -d, --detach loopdev...
              Detach  the  file  or  device associated with the specified loop
              device(s).

       -D, --detach-all
              Detach all associated loop devices.

       -f, --find
              Find the first unused  loop  device.   If  a  file  argument  is
              present,  use  the found device as loop device.  Otherwise, just
              print its name.

       -j, --associated file
              Show the status of all loop devices associated  with  the  given
              file.

       -J, --json
              Use JSON format for --list output.

       -l, --list
              If  a  loop  device  or  the  -a  option is specified, print the
              default columns for either the specified loop device or all loop
              devices;  the  default  is to print info about all devices.  See
              also --output, --noheadings --json and --raw.

       -n, --noheadings
              Don't print headings for --list output format.

       -o, --offset offset
              The data start is moved offset bytes into the specified file  or
              device.

       -O, --output columns
              Specify  the  columns that are to be printed for the --list out-
              put.

       -P, --partscan
              Force the kernel to scan the partition table on a newly  created
              loop device.

       --raw  Use the raw --list output format.

       -r, --read-only
              Set up a read-only loop device.

       --sizelimit size
              The  data  end  is set to no more than size bytes after the data
              start.

       --show Display the name of the assigned loop device if  the  -f  option
              and a file argument are present.

       -v, --verbose
              Verbose mode.

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

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

ENCRYPTION
       Cryptoloop  is  no  longer  supported  in  favor of dm-crypt.  For more
       details see cryptsetup (8).

RETURN VALUE
       losetup returns 0 on success, nonzero on failure.   When  losetup  dis-
       plays  the  status  of a loop device, it returns 1 if the device is not
       configured and 2 if an error occurred which prevented  determining  the
       status of the device.

FILES
       /dev/loop[0..N]
              loop block devices

       /dev/loop-control
              loop control device

EXAMPLE
       The  following  commands  can  be  used as an example of using the loop
       device.

              # dd if=/dev/zero of=~/file.img bs=1MiB count=10
              # losetup --find --show ~/file.img
              /dev/loop0
              # mkfs -t ext2 /dev/loop0
              # mount /dev/loop0 /mnt
               ...
              # umount /dev/loop0
              # losetup --detach /dev/loop0

ENVIRONMENT
       LOOPDEV_DEBUG=all
              enables debug output.

AUTHORS
       Karel  Zak  <kzak@redhat.com>,  based  on  the  original  version  from
       Theodore Ts'o <tytso@athena.mit.edu>

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

util-linux                         July 2014                        LOSETUP(8)