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.\" 3. 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: src/sbin/swapon/swapon.8,v 1.15.2.2 2001/12/14 15:17:56 ru Exp $ 30.\" 31.Dd September 7, 2010 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 aeiq | Ar 39.Nm swapoff Fl aq | Ar 40.Nm swapctl 41.Op Fl AeghklmsU 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. 76If the 77.Fl e 78option is used, the device will be trimmed if 79it supports trim and the trim_enabled sysctl is on. 80The 81.Fl i 82option asks user confirmation before adding a swap device. 83.Pp 84The 85.Nm swapoff 86utility removes the specified swap devices from the system. 87If the 88.Fl a 89option is used, all swap devices in 90.Pa /etc/fstab 91will be removed, unless their 92.Dq noauto 93option is also set. 94If the 95.Fl q 96option is used informational messages will not be 97written to standard output when a swap device is removed. 98Note that 99.Nm swapoff 100will fail and refuse to remove a swap device if there is insufficient 101VM (memory + remaining swap devices) to run the system. 102The 103.Nm swapoff 104utility 105must move swapped pages out of the device being removed which could 106lead to high system loads for a period of time, depending on how 107much data has been swapped out to that device. 108.Pp 109The 110.Nm swapctl 111utility exists primarily for those familiar with other 112.Bx Ns s 113and may be 114used to add, remove, or list swap devices. 115Note that the 116.Fl a 117option is used differently in 118.Nm swapctl 119and indicates that a specific list of devices should be added. 120The 121.Fl d 122option indicates that a specific list should be removed. 123The 124.Fl A 125and 126.Fl U 127options to 128.Nm swapctl 129operate on all swap entries in 130.Pa /etc/fstab 131which do not have their 132.Dq noauto 133option set. 134.Pp 135Swap information can be generated using the 136.Xr swapinfo 8 137utility, 138.Nm pstat 139.Fl s , 140or 141.Nm swapctl 142.Fl l . 143The 144.Nm swapctl 145utility has the following options for listing swap: 146.Bl -tag -width indent 147.It Fl h 148Output values in human-readable form. 149.It Fl g 150Output values in gigabytes. 151.It Fl k 152Output values in kilobytes. 153.It Fl m 154Output values in megabytes. 155.It Fl l 156List the devices making up system swap. 157.It Fl s 158Print a summary line for system swap. 159.It Fl e 160Attempts to Trim the device if -[Aa] is used. 161.It Fl i 162Asks user confirmation when -a is used. 163.Pp 164The 165.Ev BLOCKSIZE 166environment variable is used if not specifically 167overridden. 1681K blocks are used by default. 169.El 170.Sh FILES 171.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact 172.It Pa /dev/{ad,da}?s?b 173standard paging devices 174.It Pa /dev/vn?s?b 175vnode disk paging device 176.It Pa /etc/fstab 177ASCII filesystem description table 178.It Pa /etc/vntab 179ASCII vnode file table 180.El 181.Sh DIAGNOSTICS 182These utilities may fail for the reasons described in 183.Xr swapon 2 . 184.Sh SEE ALSO 185.Xr swapon 2 , 186.Xr fstab 5 , 187.Xr init 8 , 188.Xr pstat 8 , 189.Xr rc 8 , 190.Xr vnconfig 8 191.Sh HISTORY 192The 193.Nm swapon 194utility appeared in 195.Bx 4.0 . 196The 197.Nm swapoff 198and 199.Nm swapctl 200utilities appeared in 201.Fx 5.1 202and were later ported to 203.Dx 2.7 . 204