mount/losetup.8

   1 .TH LOSETUP 8 "Nov 24 1993" "Linux" "MAINTENANCE COMMANDS"
   2 .SH NAME
   3 losetup \- set up and control loop devices
   4 .SH SYNOPSIS
   5 .ad l
   6 .B losetup
   7 [
   8 .B \-e
   9 .I encryption
  10 ] [
  11 .B \-o
  12 .I offset
  13 ]
  14 .I loop_device file
  15 .br
  16 .B losetup
  17 [
  18 .B \-d
  19 ]
  20 .I loop_device
  21 .ad b
  22 .SH DESCRIPTION
  23 .B losetup
  24 is used to associate loop devices with regular files or block devices,
  25 to detach loop devices and to query the status of a loop device. If only the
  26 \fIloop_device\fP argument is given, the status of the corresponding loop
  27 device is shown.
  28 .SH OPTIONS
  29 .IP \fB\-d\fP
  30 detach the file or device associated with the specified loop device.
  31 .IP "\fB\-e \fIencryption\fP"
  32 .RS
  33 enable data encryption. The following keywords are recognized:
  34 .IP \fBNONE\fP
  35 use no encryption (default).
  36 .PD 0
  37 .IP \fBXOR\fP
  38 use a simple XOR encryption.
  39 .IP \fBDES\fP
  40 use DES encryption. DES encryption is only available if the optional
  41 DES package has been added to the kernel. DES encryption uses an additional
  42 start value that is used to protect passwords against dictionary
  43 attacks.
  44 .PD
  45 .RE
  46 .IP "\fB\-o \fIoffset\fP"
  47 the data start is moved \fIoffset\fP bytes into the specified file or
  48 device.
  49 .SH RETURN VALUE
  50 .B losetup
  51 returns 0 on success, nonzero on failure. When
  52 .B losetup
  53 displays the status of a loop device, it returns 1 if the device
  54 is not configured and 2 if an error occurred which prevented
  55 .B losetup
  56 from determining the status of the device.
  57
  58 .SH FILES
  59 .nf
  60 /dev/loop0,/dev/loop1,...   loop devices (major=7)
  61 .fi
  62 .SH EXAMPLE
  63 If you are using the loadable module you must have the module loaded
  64 first with the command
  65 .IP
  66 # insmod loop.o
  67 .LP
  68 The following commands can be used as an example of using the loop device.
  69 .nf
  70 .IP
  71 dd if=/dev/zero of=/file bs=1k count=100
  72 losetup -e des /dev/loop0 /file
  73 Password:
  74 Init (up to 16 hex digits):
  75 mkfs -t ext2 /dev/loop0 100
  76 mount -t ext2 /dev/loop0 /mnt
  77  ...
  78 umount /dev/loop0
  79 losetup -d /dev/loop0
  80 .fi
  81 .LP
  82 If you are using the loadable module you may remove the module with
  83 the command
  84 .IP
  85 # rmmod loop
  86 .LP
  87 .fi
  88 .SH RESTRICTION
  89 DES encryption is painfully slow. On the other hand, XOR is terribly weak.
  90 .SH AUTHORS
  91 .nf
  92 Original version: Theodore Ts'o <tytso@athena.mit.edu>
  93 Original DES by: Eric Young <eay@psych.psy.uq.oz.au>
  94 .fi