.TH LOSETUP 8 "July 2003" "util-linux" "System Administration"
.SH NAME
losetup \- set up and control loop devices
.SH SYNOPSIS
.ad l
Get info:
.sp
.in +5
.B losetup
.I loopdev
.sp
.B losetup -l
.RB [ \-a ]
.sp
.B losetup -j
.I file
.RB [ \-o
.IR offset ]
.sp
.in -5
Delete loop:
.sp
.in +5
.B "losetup \-d"
.IR loopdev ...
.sp
.in -5
Delete all used loop devices:
.sp
.in +5
.B "losetup \-D"
.sp
.in -5
Print name of first unused loop device:
.sp
.in +5
.B "losetup \-f"
.sp
.in -5
Setup loop device:
.sp
.in +5
.B losetup
.RB [ \-o
.IR offset ]
.RB [ \-\-sizelimit
.IR size ]
.in +8
.RB [ \-p
.IR pfd ]
.RB [ \-rP ]
.RB { \-f [ \-\-show ]| \fIloopdev\fP }
.I file
.sp
.in -13
Resize loop device:
.sp
.in +5
.B "losetup \-c"
.I loopdev
.in -5
.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
\fIloopdev\fP argument is given, the status of the corresponding loop
device is shown.

Note that the old output format (e.g. losetup -a) with comma delimited strings is
deprecated in favour of the --list output format (e.g. losetup -a -l).
.SH OPTIONS
+The \fIsize\fR and \fIoffset\fR arguments may be followed by the multiplicative
+suffixes KiB=1024, MiB=1024*1024, and so on for GiB, TiB, PiB, EiB, ZiB and YiB
+(the "iB" is optional, e.g. "K" has the same meaning as "KiB") or the suffixes
+KB=1000, MB=1000*1000, and so on for GB, TB, PB, EB, ZB and YB.

.IP "\fB\-a, \-\-all\fP"
show status of all loop devices. Note that not all information are accessible
for non-root users. See also \fB\-\-list\fP. The old output format (as printed
without --list) is deprecated.
.IP "\fB\-c, \-\-set-capacity\fP \fIloopdev\fP
force loop driver to reread size of the file associated with the specified loop device
.IP "\fB\-d, \-\-detach\fP \fIloopdev\fP..."
detach the file or device associated with the specified loop device(s)
.IP "\fB\-D, \-\-detach-all\fP"
detach all associated loop devices
.IP "\fB\-f, \-\-find\fP"
find the first unused loop device. If a
.I file
argument is present, use this device. Otherwise, print its name
.IP "\fB\-h, \-\-help\fP"
print help
.IP "\fB\-j, \-\-associated \fIfile\fP"
show status of all loop devices associated with given
.I file
.IP "\fB\-l, \-\-list"
if a loop device or the -a option is specified, print default columns for
either the specified loop device or all loop devices, default is to print info
about all devices.  See also \fB\-\-output\fP, \fB\-\-noheadings\fP
and \fB\-\-raw\fP.
.IP "\fB\-n, \fB\-\-noheadings\fP"
don't print headings for \fB\-\-list\fP output format
.IP "\fB\-o, \-\-offset \fIoffset\fP"
the data start is moved \fIoffset\fP bytes into the specified file or
device
.IP "\fB\-O, \-\-output \fIcolumns\fP"
specify which columns are to be printed for the \fB\-\-list\fP output
.IP "\fB\-\-sizelimit \fIsize\fP"
the data end is set to no more than \fIsize\fP bytes after the data start
.IP "\fB\-P, \-\-partscan\fP"
force kernel to scan partition table on newly created loop device
.IP "\fB\-\-raw\fP"
use raw \fB\-\-list\fP output format
.IP "\fB\-r, \-\-read-only\fP"
setup read-only loop device
.IP "\fB\-\-show\fP"
print device name if the
.I -f
option and a
.I file
argument are present.
.IP "\fB\-v, \-\-verbose\fP"
verbose mode

.SH ENCRYPTION
.B Cryptoloop is no longer supported in favor of dm-crypt. For more details see
.B cryptsetup(8).

.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
from determining the status of the device.

.SH FILES
.TP
.I /dev/loop[0..N]
loop block devices
.TP
.I /dev/loop-cotrol
loop control device

.SH EXAMPLE
The following commands can be used as an example of using the loop device.
.nf
.IP
# dd if=/dev/zero of=~/file.img bs=1MiB count=10
# losetup --find --show ~/file.img
/dev/loop0
# mkfs -t ext2 /dev/loop0
# mount /dev/loop0 /mnt
 ...
# umount /dev/loop0
# losetup --detach /dev/loop0
.fi
.SH AUTHORS
Karel Zak <kzak@redhat.com>, based on original version from
Theodore Ts'o <tytso@athena.mit.edu>
.SH AVAILABILITY
The losetup command is part of the util-linux package and is available from
ftp://ftp.kernel.org/pub/linux/utils/util-linux/.