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
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
-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 con-
figured 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/.
util-linux July 2003 LOSETUP(8)