Section 0: losetup
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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 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.
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
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LOSETUP(8) MAINTENANCE COMMANDS LOSETUP(8)
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.
-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)
/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.
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LOSETUP(8) MAINTENANCE COMMANDS LOSETUP(8)
BUGS
CAST, DES, RC5 and Twofish are currently broken and cannot
be used.
AUTHORS
Original version: Theodore Ts'o
Maintained by: Werner Almesberger
Original DES by: Eric Young
Modularized and updated 28-5-94: Mitch DSouza
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