losetup manpage

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LOSETUP(8)		     System Administration		    LOSETUP(8)

       losetup - set up and control loop devices

       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

       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 corre-
       sponding loop device is shown.

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

       +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 out-
	      put 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

       -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

       -P, --partscan
	      force kernel to scan  partition  table  on  newly	 created  loop

       -r, --read-only
	      setup read-only loop device

       --show print  device  name  if  the  -f	option and a file argument are

       -v, --verbose
	      verbose mode

       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  config-
       ured  and  2  if an error occurred which prevented from determining the
       status of the device.

	      loop block devices

	      loop control 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

       Karel  Zak  <kzak@redhat.com>,  based on original version from Theodore
       Ts'o <tytso@athena.mit.edu>

       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)