losetup — set up and control loop devices
losetup loopdev
losetup −l [−a]
losetup −j file [ −o offset ]
losetup −d loopdev...
losetup −D
losetup −f
losetup [
−o offset ] [
−−sizelimit
size ] [−Pr]
[−−show]
−f | loopdev
file
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. If no
option is given, all loop devices are shown.
Note that the old output format (i.e. losetup -a) with comma-delimited
strings is deprecated in favour of the −−list output format.
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,
−−allShow the status of all loop devices. Note that not
all information is accessible for non-root users. See
also −−list.
The old output format (as printed without −−list) is deprecated.
−c,
−−set−capacity loopdevForce the loop driver to reread the 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−allDetach all associated loop devices.
−−direct−io[=on|off]Enable or disable direct I/O for the backing file. The optional argument can be either on or off. If the argument is omitted, it defaults to on.
−f,
−−findFind the first unused loop device. If a file argument is present,
use the found device as loop device. Otherwise, just
print its name.
−j,
−−associated fileShow the status of all loop devices associated with
the given file.
−J,
−−jsonUse JSON format for −−list output.
−l,
−−listIf a loop device or the −a option is
specified, print the default columns for either the
specified loop device or all loop devices; the default
is to print info about all devices. See also
−−output,
−−noheadings
−−json and
−−raw.
−n,
−−noheadingsDon't print headings for −−list output format.
−o,
−−offset offsetThe data start is moved offset bytes into the
specified file or device.
−O,
−−output columnsSpecify the columns that are to be printed for the
−−list
output.
−P,
−−partscanForce the kernel to scan the partition table on a newly created loop device.
−−rawUse the raw −−list output format.
−r,
−−read−onlySet up a read-only loop device.
−−sizelimit sizeThe data end is set to no more than size bytes after the data
start.
−−showDisplay the name of the assigned loop device if the
−f option and a
file argument
are present.
−v,
−−verboseVerbose mode.
−V,
−−versionDisplay version information and exit.
−h,
−−helpDisplay help text and exit.
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 determining the status of the 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