losetup − set up and control loop devices
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
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).
+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
Cryptoloop is no longer supported in favor of dm-crypt. For more details see cryptsetup(8).
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.
/dev/loop[0..N]
loop block devices
/dev/loop-cotrol
loop control device
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
Karel Zak <kzak@redhat.com>, based on original version from Theodore Ts’o <tytso@athena.mit.edu>
The losetup command is part of the util-linux package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.