losetup

NAME

       losetup - set up and control loop devices

SYNOPSIS

       losetup [ -e encryption ] [ -o offset ] loop_device file
       losetup [ -d ] loop_device

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
       device is shown.

OPTIONS

       -d     detach the file or device associated with the spec-
              ified loop device.

       -e encryption
              enable data encryption. The following keywords  are
              recognized:

              NONE   use no encryption (default).
              XOR    use a simple XOR encryption.
              DES    use  DES  encryption. DES encryption is only
                     available if the optional  DES  package  has
                     been  added  to  the  kernel. DES encryption
                     uses an additional start value that is  used
                     to   protect  passwords  against  dictionary
                     attacks.

       -o offset
              the data start is moved offset bytes into the spec-
              ified file or device.

FILES

       /dev/loop0,/dev/loop1,...   loop devices (major=7)

EXAMPLE

       If  you  are  using  the loadable module you must have the
       module loaded first with the command

              # insmod loop.o

       The following commands can be used as an example of  using
       the loop device.

              dd if=/dev/zero of=/file bs=1k count=100
              losetup -e des /dev/loop0 /file
              Password:
              Init (up to 16 hex digits):
              mkfs -t ext2 /dev/loop0 100
              mount -t ext2 /dev/loop0 /mnt
               ...

              umount /dev/loop0
              losetup -d /dev/loop0

       If  you  are  using the loadable module you may remove the
       module with the command

              # rmmod loop

RESTRICTION

       DES encryption is painfully slow. On the other  hand,  XOR
       is terribly weak.

AUTHORS

       Original version: Theodore Ts'o <tytso@athena.mit.edu>
       Maintained by: Werner Almesberger <almesber@bernina.ethz.ch>
       Original DES by: Eric Young <eay@psych.psy.uq.oz.au>
       Modularized and updated 28-5-94: Mitch DSouza <m.dsouza@mrc-apu.cam.ac.uk>