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 April 29, 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 a | Ar 39.Nm swapoff Fl a | 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. 72.Pp 73The 74.Nm swapoff 75utility removes the specified swap devices from the system. 76If the 77.Fl a 78option is used, all swap devices in 79.Pa /etc/fstab 80will be removed, unless their 81.Dq noauto 82option is also set. 83Note that 84.Nm swapoff 85will fail and refuse to remove a swap device if there is insufficient 86VM (memory + remaining swap devices) to run the system. 87The 88.Nm swapoff 89utility 90must move swapped pages out of the device being removed which could 91lead to high system loads for a period of time, depending on how 92much data has been swapped out to that device. 93.Pp 94The 95.Nm swapctl 96utility exists primarily for those familiar with other 97.Bx Ns s 98and may be 99used to add, remove, or list swap devices. 100Note that the 101.Fl a 102option is used differently in 103.Nm swapctl 104and indicates that a specific list of devices should be added. 105The 106.Fl d 107option indicates that a specific list should be removed. 108The 109.Fl A 110and 111.Fl U 112options to 113.Nm swapctl 114operate on all swap entries in 115.Pa /etc/fstab 116which do not have their 117.Dq noauto 118option set. 119.Pp 120Swap information can be generated using the 121.Xr swapinfo 8 122utility, 123.Nm pstat 124.Fl s , 125or 126.Nm swapctl 127.Fl l . 128The 129.Nm swapctl 130utility has the following options for listing swap: 131.Bl -tag -width indent 132.It Fl h 133Output values in human-readable form. 134.It Fl g 135Output values in gigabytes. 136.It Fl k 137Output values in kilobytes. 138.It Fl m 139Output values in megabytes. 140.It Fl l 141List the devices making up system swap. 142.It Fl s 143Print a summary line for system swap. 144.Pp 145The 146.Ev BLOCKSIZE 147environment variable is used if not specifically 148overridden. 149512 byte blocks are used by default. 150.El 151.Sh FILES 152.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact 153.It Pa /dev/{ad,da}?s?b 154standard paging devices 155.It Pa /dev/md? 156memory disk devices 157.It Pa /etc/fstab 158.Tn ASCII 159file system description table 160.El 161.Sh DIAGNOSTICS 162These utilities may fail for the reasons described in 163.Xr swapon 2 . 164.Sh SEE ALSO 165.Xr swapon 2 , 166.Xr fstab 5 , 167.Xr init 8 , 168.Xr mdconfig 8 , 169.Xr pstat 8 , 170.Xr rc 8 171.Sh HISTORY 172The 173.Nm swapon 174utility appeared in 175.Bx 4.0 . 176The 177.Nm swapoff 178and 179.Nm swapctl 180utilities appeared in 181.Fx 5.1 . 182