1LOSETUP(8)                   System Administration                  LOSETUP(8)
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NAME

6       losetup - set up and control loop devices
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SYNOPSIS

9       Get info:
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11            losetup loopdev
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13            losetup -l [-a]
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15            losetup -j file [-o offset]
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17       Delete loop:
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19            losetup -d loopdev...
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21       Delete all used loop devices:
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23            losetup -D
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25       Print name of first unused loop device:
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27            losetup -f
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29       Set up a loop device:
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31            losetup [-o offset] [--sizelimit size]
32                    [-Pr] [--show] -f|loopdev file
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34       Resize loop device:
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36            losetup -c loopdev
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DESCRIPTION

39       losetup  is  used to associate loop devices with regular files or block
40       devices, to detach loop devices and to  query  the  status  of  a  loop
41       device. If only the loopdev argument is given, the status of the corre‐
42       sponding loop device is shown.
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44       Note that the old output format (e.g. losetup -a) with comma  delimited
45       strings  is deprecated in favour of the --list output format (e.g. los‐
46       etup -a -l).
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OPTIONS

49       +The size and offset arguments may be followed  by  the  multiplicative
50       +suffixes  KiB=1024,  MiB=1024*1024,  and so on for GiB, TiB, PiB, EiB,
51       ZiB and YiB +(the "iB" is optional, e.g. "K" has the  same  meaning  as
52       "KiB")  or  the  suffixes +KB=1000, MB=1000*1000, and so on for GB, TB,
53       PB, EB, ZB and YB.
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56       -a, --all
57              show status of all loop devices. Note that not  all  information
58              are accessible for non-root users. See also --list. The old out‐
59              put format (as printed without --list) is deprecated.
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61       -c, --set-capacity loopdev
62              force loop driver to reread size of the file associated with the
63              specified loop device
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65       -d, --detach loopdev...
66              detach  the  file  or  device associated with the specified loop
67              device(s). Note that since Linux v3.7 kernel uses  "lazy  device
68              destruction".   The detach operation does not return EBUSY error
69              anymore if device is actively used by system, but it  is  marked
70              by autoclear flag and destroyed later.
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72       -D, --detach-all
73              detach all associated loop devices
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75       -f, --find
76              find  the  first  unused  loop  device.  If  a  file argument is
77              present, use this device. Otherwise, print its name
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79       -h, --help
80              print help
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82       -j, --associated file
83              show status of all loop devices associated with given file
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85       -l, --list
86              if a loop device or the -a option is  specified,  print  default
87              columns  for  either  the  specified  loop  device  or  all loop
88              devices, default is to print info about all devices.
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90       -o, --offset offset
91              the data start is moved offset bytes into the specified file  or
92              device
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94       -O, --output columns
95              specify which columns are to be printed for the --list output
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97       --sizelimit size
98              the  data  end  is set to no more than size bytes after the data
99              start
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101       -P, --partscan
102              force kernel to scan  partition  table  on  newly  created  loop
103              device
104
105       -r, --read-only
106              setup read-only loop device
107
108       --show print  device  name  if  the  -f  option and a file argument are
109              present.
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111       -v, --verbose
112              verbose mode
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ENCRYPTION

116       Cryptoloop is no longer  supported  in  favor  of  dm-crypt.  For  more
117       details see cryptsetup(8).
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RETURN VALUE

121       losetup returns 0 on success, nonzero on failure. When losetup displays
122       the status of a loop device, it returns 1 if the device is not  config‐
123       ured  and  2  if an error occurred which prevented from determining the
124       status of the device.
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126

FILES

128       /dev/loop[0..N]
129              loop block devices
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131       /dev/loop-cotrol
132              loop control device
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134

EXAMPLE

136       The following commands can be used as an  example  of  using  the  loop
137       device.
138
139              # dd if=/dev/zero of=~/file.img bs=1MiB count=10
140              # losetup --find --show ~/file.img
141              /dev/loop0
142              # mkfs -t ext2 /dev/loop0
143              # mount /dev/loop0 /mnt
144               ...
145              # umount /dev/loop0
146              # losetup --detach /dev/loop0
147

AUTHORS

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

153       The losetup command is part of the util-linux package and is  available
154       from ftp://ftp.kernel.org/pub/linux/utils/util-linux/.
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158util-linux                         July 2003                        LOSETUP(8)
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