LOSETUP(8)

NAME
losetup - set up and control loop devices

SYNOPSIS
Get info:

losetup loopdev

losetup -l [-a]

losetup -j file [-o offset]

Delete loop:

losetup -d loopdev...

Delete all used loop devices:

losetup -D

Print name of first unused loop device:

losetup -f

Set up a loop device:

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

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

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 status of all loop devices. Note that not all information are accessible for non-root users. See also --list. The old output format (as printed without --list) is deprecated.

-c, --set-capacity loopdev
    force loop driver to reread 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 this device. Otherwise, print its name

-h, --help
    print help

-j, --associated file
    show status of all loop devices associated with given file

-l, --list
    if a loop device or the -a option is specified, print default columns for either the specified loop device or all loop devices, default is to print info about all devices.

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

-O, --output columns
    specify which columns are to be printed for the --list output

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

-P, --partscan
    force kernel to scan partition table on newly created loop device

-r, --read-only
    setup read-only loop device

--show
    print device name if the -f option and a file argument are present.

-v, --verbose
    verbose mode

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 from determining the status of the device.

FILES

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

/dev/loop-cotrol
    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

AUTHORS
Karel Zak <kzak@redhat.com>, based on 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/.