.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 [ \-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. If no option is given, all loop devices are shown.
Note that the old output format (e.g. losetup -a) with comma delimited strings is
deprecated in favour of the --list output format.
.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-control
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/.
