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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 02:42:50 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-06 02:42:50 +0000
commit8cb83eee5a58b1fad74c34094ce3afb9e430b5a4 (patch)
treea9b2e7baeca1be40eb734371e3c8b11b02294497 /sys-utils/losetup.8
parentInitial commit. (diff)
downloadutil-linux-8cb83eee5a58b1fad74c34094ce3afb9e430b5a4.tar.xz
util-linux-8cb83eee5a58b1fad74c34094ce3afb9e430b5a4.zip
Adding upstream version 2.33.1.upstream/2.33.1upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.TH LOSETUP 8 "November 2015" "util-linux" "System Administration"
+.SH NAME
+losetup \- set up and control loop devices
+.SH SYNOPSIS
+.ad l
+Get info:
+.sp
+.in +5
+.B losetup
+[\fIloopdev\fP]
+.sp
+.B losetup -l
+.RB [ \-a ]
+.sp
+.B losetup -j
+.I file
+.RB [ \-o
+.IR offset ]
+.sp
+.in -5
+Detach a loop device:
+.sp
+.in +5
+.B "losetup \-d"
+.IR loopdev ...
+.sp
+.in -5
+Detach all associated loop devices:
+.sp
+.in +5
+.B "losetup \-D"
+.sp
+.in -5
+Set up a loop device:
+.sp
+.in +5
+.B losetup
+.RB [ \-o
+.IR offset ]
+.RB [ \-\-sizelimit
+.IR size ]
+.RB [ \-\-sector\-size
+.IR size ]
+.in +8
+.RB [ \-Pr ]
+.RB [ \-\-show ] " \-f" | \fIloopdev\fP
+.I file
+.sp
+.in -13
+Resize a 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.
+.sp
+Note that the old output format (i.e., \fBlosetup -a\fR) with comma-delimited
+strings is deprecated in favour of the \fB--list\fR output format.
+.sp
+It's possible to create more independent loop devices for the same backing
+file.
+.B This setup may be dangerous, can cause data loss, corruption and overwrites.
+Use \fB\-\-nooverlap\fR with \fB\-\-find\fR during setup to avoid this problem.
+
+.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.
+
+.TP
+.BR \-a , " \-\-all"
+Show the status of all loop devices. Note that not all information is accessible
+for non-root users. See also \fB\-\-list\fR. The old output format (as printed
+without \fB--list)\fR is deprecated.
+.TP
+.BR \-d , " \-\-detach " \fIloopdev\fR...
+Detach the file or device associated with the specified loop device(s). Note
+that since Linux v3.7 kernel uses "lazy device destruction". The detach
+operation does not return EBUSY error anymore if device is actively used by
+system, but it is marked by autoclear flag and destroyed later.
+.TP
+.BR \-D , " \-\-detach\-all"
+Detach all associated loop devices.
+.TP
+.BR \-f , " \-\-find " "\fR[\fIfile\fR]"
+Find the first unused loop device. If a \fIfile\fR argument is present, use
+the found device as loop device. Otherwise, just print its name.
+.IP "\fB\-\-show\fP"
+Display the name of the assigned loop device if the \fB\-f\fP option and a
+\fIfile\fP argument are present.
+.TP
+.BR \-L , " \-\-nooverlap"
+Check for conflicts between loop devices to avoid situation when the same
+backing file is shared between more loop devices. If the file is already used
+by another device then re-use the device rather than a new one. The option
+makes sense only with \fB\-\-find\fP.
+.TP
+.BR \-j , " \-\-associated " \fIfile\fR " \fR[\fB\-o \fIoffset\fR]"
+Show the status of all loop devices associated with the given \fIfile\fR.
+.TP
+.BR \-o , " \-\-offset " \fIoffset
+The data start is moved \fIoffset\fP bytes into the specified file or device. The \fIoffset\fP
+may be followed by the multiplicative suffixes; see above.
+.IP "\fB\-\-sizelimit \fIsize\fP"
+The data end is set to no more than \fIsize\fP bytes after the data start. The \fIsize\fP
+may be followed by the multiplicative suffixes; see above.
+.TP
+.BR \-b , " \-\-sector-size " \fIsize
+Set the logical sector size of the loop device in bytes (since Linux 4.14). The
+option may be used when create a new loop device as well as stand-alone command
+to modify sector size of the already existing loop device.
+.TP
+.BR \-c , " \-\-set\-capacity " \fIloopdev
+Force the loop driver to reread the size of the file associated with the
+specified loop device.
+.TP
+.BR \-P , " \-\-partscan"
+Force the kernel to scan the partition table on a newly created loop device.
+.TP
+.BR \-r , " \-\-read\-only"
+Set up a read-only loop device.
+.TP
+.BR \-\-direct\-io [ =on | off ]
+Enable or disable direct I/O for the backing file. The optional argument
+can be either \fBon\fR or \fBoff\fR. If the argument is omitted, it defaults
+to \fBon\fR.
+.TP
+.BR \-v , " \-\-verbose"
+Verbose mode.
+.TP
+.BR \-l , " \-\-list"
+If a loop device or the \fB-a\fR option is specified, print the default columns
+for either the specified loop device or all loop devices; the default is to
+print info about all devices. See also \fB\-\-output\fP, \fB\-\-noheadings\fP,
+\fB\-\-raw\fP, and \fB\-\-json\fP.
+.TP
+.BR \-O , " \-\-output " \fIcolumn\fR[,\fIcolumn\fR]...
+Specify the columns that are to be printed for the \fB\-\-list\fP output.
+Use \fB\-\-help\fR to get a list of all supported columns.
+.TP
+.B \-\-output\-all
+Output all available columns.
+.TP
+.BR \-n , " \-\-noheadings"
+Don't print headings for \fB\-\-list\fP output format.
+.IP "\fB\-\-raw\fP"
+Use the raw \fB\-\-list\fP output format.
+.TP
+.BR \-J , " \-\-json"
+Use JSON format for \fB\-\-list\fP output.
+.TP
+.BR \-V , " \-\-version"
+Display version information and exit.
+.TP
+.BR \-h , " \-\-help"
+Display help text and exit.
+
+.SH ENCRYPTION
+.B Cryptoloop is no longer supported in favor of dm-crypt.
+.B For more details see 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
+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=1024k 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 ENVIRONMENT
+.IP LOOPDEV_DEBUG=all
+enables debug output.
+.SH AUTHORS
+Karel Zak <kzak@redhat.com>, based on the 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
+https://www.kernel.org/pub/linux/utils/util-linux/.