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.TH LOSETUP 8 "Nov 24 1993" "Linux" "MAINTENANCE COMMANDS"
.SH NAME
losetup \- set up and control loop devices
.SH SYNOPSIS
.ad l
.B losetup
[
.B \-e
.I encryption
] [
.B \-o
.I offset
]
.I loop_device file
.br
.B losetup
[
.B \-d
]
.I loop_device
.ad b
.SH DESCRIPTION
.B 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
\fIloop_device\fP argument is given, the status of the corresponding loop
device is shown.
.SH OPTIONS
.IP \fB\-d\fP
detach the file or device associated with the specified loop device.
.IP "\fB\-e \fIencryption\fP"
.RS
enable data encryption. The following keywords are recognized:
.IP \fBNONE\fP
use no encryption (default).
.PD 0
.IP \fBXOR\fP
use a simple XOR encryption.
.IP \fBDES\fP
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.
.PD
.RE
.IP "\fB\-o \fIoffset\fP"
the data start is moved \fIoffset\fP bytes into the specified file or
device.
.SH RETURN VALUE
.B losetup
returns 0 on success, nonzero on failure. When
.B 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
.B losetup
from determining the status of the device.
.SH FILES
.nf
/dev/loop0,/dev/loop1,... loop devices (major=7)
.fi
.SH EXAMPLE
If you are using the loadable module you must have the module loaded
first with the command
.IP
# insmod loop.o
.LP
The following commands can be used as an example of using the loop device.
.nf
.IP
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
.fi
.LP
If you are using the loadable module you may remove the module with
the command
.IP
# rmmod loop
.LP
.fi
.SH RESTRICTION
DES encryption is painfully slow. On the other hand, XOR is terribly weak.
.SH AUTHORS
.nf
Original version: Theodore Ts'o <tytso@athena.mit.edu>
Original DES by: Eric Young <eay@psych.psy.uq.oz.au>
.fi
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