losetup

LOSETUP(8)                   MAINTENANCE COMMANDS                   LOSETUP(8)



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  specified  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 specified file  or
              device.

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  config-
       ured  and 2 if an error occurred which prevented losetup from determin-
       ing the status of the 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>
       Original DES by: Eric Young <eay@psych.psy.uq.oz.au>



Linux                             Nov 24 1993                       LOSETUP(8)