LOSETUP(8) System Administration LOSETUP(8)NAMElosetup - set up and control loop devices
SYNOPSIS
Get info:
losetup loopdev
losetup-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 [{-e|-E} encryption] [-o offset] [--sizelimit size]
[-p pfd] [-rP] {-f[--show]|loopdev} file
Resize loop device:
losetup-c loopdev
DESCRIPTIONlosetup 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 corre‐
sponding loop device is shown.
OPTIONS
The size and offset arguments may be followed by binary (2^N) suffixes
KiB, MiB, GiB, TiB, PiB and EiB (the "iB" is optional, e.g. "K" has the
same meaning as "KiB") or decimal (10^N) suffixes KB, MB, GB, PB and
EB.
-a, --all
show status of all loop devices. Note that not all information
are accessible for non-root users.
-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
-e, -E, --encryption encryption_type
enable data encryption with specified name or number
-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
-o, --offset offset
the data start is moved offset bytes into the specified file or
device
--sizelimit size
the data end is set to no more than size bytes after the data
start
-p, --pass-fd num
read the passphrase from file descriptor with number num instead
of from the terminal
-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 deprecated in favor of dm-crypt. For more details see
cryptsetup (8). It is possible that all bug reports regarding to -E/-e
options will be ignored.
It is possible to specify transfer functions (for encryption/decryption
or other purposes) using one of the -E and -e options. There are two
mechanisms to specify the desired encryption: by number and by name. If
an encryption is specified by number then one has to make sure that the
Linux kernel knows about the encryption with that number, probably by
patching the kernel. Standard numbers that are always present are 0 (no
encryption) and 1 (XOR encryption). When the cryptoloop module is
loaded (or compiled in), it uses number 18. This cryptoloop module
will take the name of an arbitrary encryption type and find the module
that knows how to perform that encryption.
RETURN VALUElosetup returns 0 on success, nonzero on failure. When losetup displays
the status of a loop device, it returns 1 if the device is not config‐
ured 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)
