LOSETUP(P)             MAINTENANCE COMMANDS            LOSETUP(P)



NAME
       losetup - set up and control loop devices

SYNOPSIS
       losetup [ -e encryption ] [ -o offset ] [ -p num ]
       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
       --delete, --detach, -d
              detach the file or device associated with the spec-
              ified loop device.

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

              NONE   use no encryption (default).
              XOR    use a simple XOR encryption.
              AES    use Advanced Encryption Standard encryption.
                     AES  encryption is only available if you are
                     using  the  international  kernel  and   AES
                     encryption  has  been  enabled in the Crypto
                     API.  enabled in the Crypto API.
              Blowfish
                     use Blowfish encryption. Blowfish encryption
                     is  only  available  if  you  are  using the
                     international kernel and Blowfish encryption
                     has been enabled in the Crypto API.
              Twofish
                     use  Twofish  encryption. Twofish encryption
                     is only  available  if  you  are  using  the
                     international  kernel and Twofish encryption
                     has been enabled in the Crypto API.
              CAST   use CAST encryption. CAST encryption is only
                     available if you are using the international
                     kernel and CAST encryption has been  enabled
                     in the Crypto API.
              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. Use of DES is deprecated.
              DFC    use DFC encryption. DFC encryption  is  only
                     available if you are using the international
                     kernel and DFC encryption has  been  enabled
                     in the Crypto API.
              IDEA   use IDEA encryption. IDEA encryption is only
                     available if you are using the international
                     kernel  and IDEA encryption has been enabled
                     in the Crypto API.
              MARS   use MARS encryption. MARS encryption is only
                     available if you are using the international
                     kernel and MARS encryption has been  enabled
                     in the Crypto API.
              RC5    use  RC5  encryption. RC5 encryption is only
                     available if you are using the international
                     kernel  and  RC5 encryption has been enabled
                     in the Crypto API.
              RC6    use RC6 encryption. RC6 encryption  is  only
                     available if you are using the international
                     kernel and RC6 encryption has  been  enabled
                     in the Crypto API.
              Serpent
                     use  Serpent  encryption. Serpent encryption
                     is only  available  if  you  are  using  the
                     international  kernel and Serpent encryption
                     has been enabled in the Crypto API.

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

       --pass-fd, -p num
              read   the  passphrase  from  file  descriptor  num
              instead of the terminal.

       --keybits, -k num
              set the number of bits to use in key to num.

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 configured and 2 if an error occurred
       which prevented losetup from determining the status of the
       device.


FILES
       /dev/loop0,/dev/loop1,...   loop devices (major=7)
       /proc/cipher/*              available ciphers

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 blowfish /dev/loop0 /file
              Password :
              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


RESTRICTIONS
       DES  encryption  is painfully slow. On the other hand, XOR
       is terribly weak. Both are insecure nowadays. Some ciphers
       require a licence for you to be allowed to use them.

BUGS
       CAST, DES, RC5 and Twofish are currently broken and cannot
       be used.

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(P)