Section (8) losetup
losetup — set up and control loop devices
- Get info:
- Detach a loop device:
- Detach all associated loop devices:
- Set up a loop device:
−ooffset ] [
−−sizelimitsize ] [
−−sector−sizesize ] [
−f| loopdev file
- Resize a loop device:
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.
It_zsingle_quotesz_s possible to create more independent loop devices for
the same backing file. This setup
may be dangerous, can cause data loss, corruption and
−−find during setup to avoid this
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
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.
Detach all associated loop devices.
−f, −−find [
Find the first unused loop device. If a
fileargument is present, use the found device as loop device. Otherwise, just print its name.
Display the name of the assigned loop device if the
−foption and a
fileargument are present.
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
Show the status of all loop devices associated with the given
The data start is moved
offsetbytes into the specified file or device. The
offsetmay be followed by the multiplicative suffixes; see above.
The data end is set to no more than
sizebytes after the data start. The
sizemay be followed by the multiplicative suffixes; see above.
Set the logical sector size of the loop device in bytes (since Linux 4.14). The option may be used when create a new loop device as well as stand-alone command to modify sector size of the already existing loop device.
Force the loop driver to reread the size of the file associated with the specified loop device.
Force the kernel to scan the partition table on a newly created loop device.
Set up a read-only loop device.
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.
If a loop device or the
−aoption 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
Specify the columns that are to be printed for the
−−helpto get a list of all supported columns.
Output all available columns.
Don_zsingle_quotesz_t print headings for
Use the raw
Use JSON format for
Display version information and exit.
Display 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=1024k 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