losetup loopdevlosetup -l [-a]
losetup -j file [-o offset]
Detach a loop device:
losetup -d loopdev...
Detach all associated loop devices:
Print the name of the first unused loop device:
Set up a loop device:
losetup [-o offset] [--sizelimit size]
[-Pr] [--show] -f|loopdev file
Resize a 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. 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
It's possible to create more independent loop devices for the same
backing file. This setup may be dangerous, can cause data loss,corruption and overwrites. Use --nooverlap to avoid this problem.
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.
Show 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
-c, --set-capacity loopdev
Force 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
Detach all associated loop devices.
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.
Find the first unused loop device. If a file argument is
present, use the found device as loop device. Otherwise, just
print its name.
Check for conflicts between loop devices to avoid situation
when the same backing file is shared between more loop
devices. If the file is already used by another device then
re-use the device rather than a new one. The option makes
sense only with --find.
-j, --associated file
Show the status of all loop devices associated with the given
Use JSON format for --list output.
If 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.
Don't print headings for --list output format.
-o, --offset offset
The data start is moved offset bytes into the specified file
-O, --output columns
Specify the columns that are to be printed for the --list
Force the kernel to scan the partition table on a newly
created loop device.
--raw Use the raw --list output format.
Set up a read-only loop device.
The data end is set to no more than size bytes after the data
--show Display the name of the assigned loop device if the -f option
and a file argument are present.
Display version information and exit.
Display help text and exit.
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
# dd if=/dev/zero of=~/file.img bs=1MiB count=10
# losetup --find --show ~/file.img
# mkfs -t ext2 /dev/loop0
# mount /dev/loop0 /mnt
# umount /dev/loop0
# losetup --detach /dev/loop0
This page is part of the util-linux (a random collection of Linux
utilities) project. Information about the project can be found at
⟨https://www.kernel.org/pub/linux/utils/util-linux/⟩. If you have a
bug report for this manual page, send it to
email@example.com. This page was obtained from the
project's upstream Git repository
2016-10-04. If you discover any rendering problems in this HTML ver‐
sion of the page, or you believe there is a better or more up-to-date
source for the page, or you have corrections or improvements to the
information in this COLOPHON (which is not part of the original man‐
ual page), send a mail to firstname.lastname@example.org
util-linux November 2015 LOSETUP(8)