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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]
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 depre-
cated 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). Note that
since Linux v3.7 kernel uses "lazy device destruction". The detach operation does
not return EBUSY error anymore if device is actively used by system, but it is
marked by autoclear flag and destroyed later.
-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 crypt-
setup(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 AT redhat.com>, based on original version from Theodore Ts'o
<tytso AT athena.edu>
AVAILABILITY
The losetup command is part of the util-linux package and is available from ftp://ftp.ker-
nel.org/pub/linux/utils/util-linux/.
util-linux July 2003 LOSETUP(8)
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On Apache/2.4.6 (CentOS)
Under GNU General Public License
2025-06-23 22:04 @127.0.0.1 CrawledBy Wget/1.21.2