1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 4. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)swapon.8 8.1 (Berkeley) 6/5/93 29.\" $FreeBSD$ 30.\" 31.Dd June 23, 2008 32.Dt SWAPON 8 33.Os 34.Sh NAME 35.Nm swapon , swapoff , swapctl 36.Nd "specify devices for paging and swapping" 37.Sh SYNOPSIS 38.Nm swapon Fl aq | Ar 39.Nm swapoff Fl aq | Ar 40.Nm swapctl 41.Op Fl AghklmsU 42.Oo 43.Fl a Ar 44| 45.Fl d Ar 46.Oc 47.Sh DESCRIPTION 48The 49.Nm swapon , swapoff 50and 51.Nm swapctl 52utilities are used to control swap devices in the system. 53At boot time all swap entries in 54.Pa /etc/fstab 55are added automatically when the system goes multi-user. 56Swap devices use a fixed interleave; the maximum number of devices 57is specified by the kernel configuration option 58.Dv NSWAPDEV , 59which is typically set to 4. 60There is no priority mechanism. 61.Pp 62The 63.Nm swapon 64utility adds the specified swap devices to the system. 65If the 66.Fl a 67option is used, all swap devices in 68.Pa /etc/fstab 69will be added, unless their 70.Dq noauto 71option is also set. 72If the 73.Fl q 74option is used informational messages will not be 75written to standard output when a swap device is added. 76.Pp 77The 78.Nm swapoff 79utility removes the specified swap devices from the system. 80If the 81.Fl a 82option is used, all swap devices in 83.Pa /etc/fstab 84will be removed, unless their 85.Dq noauto 86option is also set. 87If the 88.Fl q 89option is used informational messages will not be 90written to standard output when a swap device is removed. 91Note that 92.Nm swapoff 93will fail and refuse to remove a swap device if there is insufficient 94VM (memory + remaining swap devices) to run the system. 95The 96.Nm swapoff 97utility 98must move swapped pages out of the device being removed which could 99lead to high system loads for a period of time, depending on how 100much data has been swapped out to that device. 101.Pp 102The 103.Nm swapctl 104utility exists primarily for those familiar with other 105.Bx Ns s 106and may be 107used to add, remove, or list swap devices. 108Note that the 109.Fl a 110option is used differently in 111.Nm swapctl 112and indicates that a specific list of devices should be added. 113The 114.Fl d 115option indicates that a specific list should be removed. 116The 117.Fl A 118and 119.Fl U 120options to 121.Nm swapctl 122operate on all swap entries in 123.Pa /etc/fstab 124which do not have their 125.Dq noauto 126option set. 127.Pp 128Swap information can be generated using the 129.Xr swapinfo 8 130utility, 131.Nm pstat 132.Fl s , 133or 134.Nm swapctl 135.Fl l . 136The 137.Nm swapctl 138utility has the following options for listing swap: 139.Bl -tag -width indent 140.It Fl h 141Output values in human-readable form. 142.It Fl g 143Output values in gigabytes. 144.It Fl k 145Output values in kilobytes. 146.It Fl m 147Output values in megabytes. 148.It Fl l 149List the devices making up system swap. 150.It Fl s 151Print a summary line for system swap. 152.Pp 153The 154.Ev BLOCKSIZE 155environment variable is used if not specifically 156overridden. 157512 byte blocks are used by default. 158.El 159.Sh FILES 160.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact 161.It Pa /dev/{ad,da}?s?b 162standard paging devices 163.It Pa /dev/md? 164memory disk devices 165.It Pa /etc/fstab 166.Tn ASCII 167file system description table 168.El 169.Sh DIAGNOSTICS 170These utilities may fail for the reasons described in 171.Xr swapon 2 . 172.Sh SEE ALSO 173.Xr swapon 2 , 174.Xr fstab 5 , 175.Xr init 8 , 176.Xr mdconfig 8 , 177.Xr pstat 8 , 178.Xr rc 8 179.Sh HISTORY 180The 181.Nm swapon 182utility appeared in 183.Bx 4.0 . 184The 185.Nm swapoff 186and 187.Nm swapctl 188utilities appeared in 189.Fx 5.1 . 190