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
       corresponding 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 information  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 output.

       -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 displays 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)