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

Setup loop device:

losetup [ −o offset ] [ −−sizelimit size ] [ −p pfd ] [−rP] −f [−−show] | 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

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/.