losetup - Unix, Linux Command

NAME

losetup: set up and control loop devices.

SYNOPSIS

 losetup loopdev

    losetup -l [-a]

    losetup -j file [-o offset]

       Detach a loop device:

        losetup -d loopdev...

       Detach all associated loop devices:

            losetup -D

       Print the name of the first unused loop device:

            losetup -f

       Set up a loop device:

            losetup [-o offset] [--sizelimit size]
                    [-Pr] [--show] -f|loopdev file

       Resize a loop device:

            losetup -c loopdev

DESCRIPTION

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 loop_device argument is given, the status of the corresponding loop deviceis shown.

Options

Tag	Description
-a, --all	show status of all loop devices.
-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 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 limit	the data end is set to no more than sizelimit bytes after the data start.
-p, --pass-fd num	read the passphrase from file descriptor with number num instead of from the terminal.
-r, --read-only	setup read-only loop device.
--show	print device name if the -f option and a file argument are present.The short form of this option (-s) is deprecated. This short form could be in collision with Loop-AES implementation where the same option is used for --sizelimit..
-v, --verbose	verbose mode.

EXAMPLES

Example-1:

To detach file or device associated with loop device :

# losetup -e des /dev/loop0 /file

# losetup -d /dev/loop0

Example-2:

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

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