NAME    [Toc]    [Back]

       losetup - set up and control loop devices

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

       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    [Toc]    [Back]

       --delete, --detach, -d
	      detach the file or device associated  with  the  specified  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 specified 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    [Toc]    [Back]

       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    [Toc]    [Back]

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

EXAMPLE    [Toc]    [Back]

       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    [Toc]    [Back]

       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    [Toc]    [Back]

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

AUTHORS    [Toc]    [Back]

       Original version: Theodore Ts'o <[email protected]>
       Original DES by: Eric Young <[email protected]>



Linux				  Nov 24 1993			    LOSETUP(8)