losetup(8) - phpMan

LOSETUP(8)                            System Administration                            LOSETUP(8)



NAME
       losetup - set up and control loop devices

SYNOPSIS
       Get info:

            losetup loopdev

            losetup -l [-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

       Set up a loop device:

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

       Resize 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  loopdev  argument  is
       given, the status of the corresponding loop device is shown.

       Note  that  the old output format (e.g. losetup -a) with comma delimited strings is depre-
       cated in favour of the --list output format (e.g. losetup -a -l).

OPTIONS
       +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, --all
              show  status  of all loop devices. Note that not all information are accessible for
              non-root users. See also --list. The old output format (as printed without  --list)
              is deprecated.

       -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).  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.

       -D, --detach-all
              detach all associated loop devices

       -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

       -l, --list
              if a loop device or the -a option is specified, print default  columns  for  either
              the  specified  loop device or all loop devices, default is to print info about all
              devices.

       -o, --offset offset
              the data start is moved offset bytes into the specified file or device

       -O, --output columns
              specify which columns are to be printed for the --list output

       --sizelimit size
              the data end is set to no more than size bytes after the data start

       -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 no longer supported in favor  of  dm-crypt.  For  more  details  see  crypt-
       setup(8).


RETURN VALUE
       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 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 AT redhat.com>,   based   on   original   version   from   Theodore  Ts'o
       <tytso AT athena.edu>

AVAILABILITY
       The losetup command is part of the util-linux package and is available from ftp://ftp.ker-
       nel.org/pub/linux/utils/util-linux/.



util-linux                                  July 2003                                  LOSETUP(8)

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