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[thirdparty/util-linux.git] / mount / swapon.8

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.\"     @(#)swapon.8	6.3 (Berkeley) 3/16/91
.\"
.\" Sun Dec 27 12:31:30 1992: Modified by faith@cs.unc.edu
.\" Sat Mar  6 20:46:02 1993: Modified by faith@cs.unc.edu
.\" Sat Oct  9 09:35:30 1993: Converted to man format by faith@cs.unc.edu
.\" Sat Nov 27 20:22:42 1993: Updated authorship information, faith@cs.unc.edu
.\" Mon Sep 25 14:12:38 1995: Added -v and -p information
.\" Tue Apr 30 03:32:07 1996: Added some text from A. Koppenhoefer
.\"
.TH SWAPON 8 "25 September 1995" "Linux 1.x" "Linux Programmer's Manual"
.SH NAME
swapon, swapoff \- enable/disable devices and files for paging and swapping
.SH SYNOPSIS
.B /sbin/swapon [\-h \-V]
.br
.B /sbin/swapon \-a [\-v] [\-e]
.br
.BI "/sbin/swapon [\-v] [\-p " "priority" "] " " specialfile " ...
.br
.B /sbin/swapon [\-s]
.br
.B /sbin/swapoff [\-h \-V]
.br
.B /sbin/swapoff \-a
.br
.BI /sbin/swapoff " specialfile " ...
.SH DESCRIPTION
.B Swapon
is used to specify devices on which paging and swapping are to take place.

The device or file used is given by the
.I specialfile
parameter. It may be of the form
.BI \-L " label"
or
.BI \-U " uuid"
to indicate a device by label or uuid.

Calls to
.B swapon
normally occur in the system multi-user initialization file
.I /etc/rc
making all swap devices available, so that the paging and swapping activity
is interleaved across several devices and files.

Normally, the first form is used:
.TP
.B \-a
All devices marked as ``swap'' swap devices in
.I /etc/fstab
are made available, except for those with the ``noauto'' option.
Devices that are already running as swap are silently skipped.
.TP 
.B \-e
When 
.B \-a 
is used with swapon, 
.B \-e 
makes swapon silently skip devices that do not exist.
.TP
.B \-h
Provide help
.TP
.BI \-L " label"
Use the partition that has the specified
.IR label .
(For this, access to
.I /proc/partitions
is needed.)
.TP
.BI \-p " priority"
Specify priority for
.BR swapon .
This option is only available if
.B swapon
was compiled under and is used under a 1.3.2 or later kernel.
.I priority
is a value between 0 and 32767. Higher numbers indicate higher
priority. See
.BR swapon (2)
for a full description of swap priorities. Add
.BI pri= value
to the option field of
.I /etc/fstab
for use with
.BR "swapon -a" .
.TP
.B \-s
Display swap usage summary by device. Equivalent to "cat /proc/swaps".
Not available before Linux 2.1.25.
.TP
.BI \-U " uuid"
Use the partition that has the specified
.IR uuid .
(For this, access to
.I /proc/partitions
is needed.)
.TP
.B \-v
Be verbose.
.TP
.B \-V
Display version
.PP
.B Swapoff
disables swapping on the specified devices and files.
When the
.B \-a
flag is given, swapping is disabled on all known swap devices and files
(as found in
.I /proc/swaps
or
.IR /etc/fstab ).
.SH NOTE
You should not use
.B swapon
on a file with holes.
Swap over NFS may not work.
.SH SEE ALSO
.BR swapon (2),
.BR swapoff (2),
.BR fstab (5),
.BR init (8),
.BR mkswap (8),
.BR rc (8),
.BR mount (8)
.SH FILES
.I /dev/hd??
standard paging devices
.br
.I /dev/sd??
standard (SCSI) paging devices
.br
.I /etc/fstab
ascii filesystem description table
.SH HISTORY
The
.B swapon
command appeared in 4.0BSD.