Seth Woolley's Man Viewer

losetup(8) - losetup, losetup - set up and control loop devices - man 8 losetup

([section] manual, -k keyword, -K [section] search, -f whatis)
man plain no title

LOSETUP(8)                   MAINTENANCE COMMANDS                   LOSETUP(8)

       losetup - set(7,n,1 builtins) up and control loop devices

       Get info:

            losetup loop_device

       Delete loop:

            losetup -d loop_device

       Print name of first unused loop device:

            losetup -f

       Setup loop device:

            losetup [{-e|-E} encryption] [-o offset] [-p pfd]
                    {-f|loop_device} file(1,n)

       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.

       It is possible to specify transfer functions (for encryption/decryption
       or  other  purposes) using one of the -E and -e options.  There are two
       mechanisms to specify the desired encryption: by number and by name. If
       an encryption is specified by number then one has to make sure that the
       Linux kernel knows about the encryption with that number,  probably  by
       patching the kernel. Standard numbers that are always present are 0 (no
       encryption) and 1 (XOR encryption).   When  the  cryptoloop  module  is
       loaded (or compiled in(1,8)), it uses number 18.  This cryptoloop module wil
       take the name of an arbitrary encryption type and finds the module that
       knows  how to perform that encryption.  (Thus, either one uses a number
       different from 18 with the -E option, or one uses a name  with  the  -e

       -d     Detach  the  file(1,n)  or  device associated with the specified loop

       -E encryption_type
              Enable data encryption with specified number.

       -e encryption_name
              Enable data encryption with specified name.

       -f     Find the first  unused  loop  device.  If  a  file(1,n)  argument  is
              present, use this device. Otherwise, print its name.

       -o offset
              The  data start is moved offset bytes into the specified file(1,n) or

       -p num Read the passphrase from file(1,n) descriptor with number num instead
              of from the terminal.

       losetup returns 0 on success, nonzero on failure. When losetup displays
       the status of a loop device, it returns 1 if(3,n) the device is not  config-
       ured  and 2 if(3,n) an error(8,n) occurred which prevented losetup from determin-
       ing the status of the device.

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

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

              # insmod loop.o

       Maybe also encryption modules are needed.

              # insmod des.o # insmod cryptoloop.o

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

              # dd if(3,n)=/dev/zero of=/file(1,n) bs=1k count=100
              # losetup -e des /dev/loop0 /file(1,n)
              Init (up to 16 hex digits):
              # mkfs -t ext2 /dev/loop0 100
              # mount(2,8) -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

              # rmmod loop

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

Linux                             2003-07-01                        LOSETUP(8)

References for this manual (incoming links)