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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)swapon.8 8.1 (Berkeley) 6/5/93 33.\" $FreeBSD: src/sbin/swapon/swapon.8,v 1.15.2.2 2001/12/14 15:17:56 ru Exp $ 34.\" $DragonFly: src/sbin/swapon/swapon.8,v 1.4 2007/08/10 18:28:27 swildner Exp $ 35.\" 36.Dd September 7, 2010 37.Dt SWAPON 8 38.Os 39.Sh NAME 40.Nm swapon , swapoff , swapctl 41.Nd "specify devices for paging and swapping" 42.Sh SYNOPSIS 43.Nm swapon Fl aeq | Ar 44.Nm swapoff Fl aq | Ar 45.Nm swapctl 46.Op Fl AeghklmsU 47.Oo 48.Fl a Ar 49| 50.Fl d Ar 51.Oc 52.Sh DESCRIPTION 53The 54.Nm swapon , swapoff 55and 56.Nm swapctl 57utilities are used to control swap devices in the system. 58At boot time all swap entries in 59.Pa /etc/fstab 60are added automatically when the system goes multi-user. 61Swap devices use a fixed interleave; the maximum number of devices 62is specified by the kernel configuration option 63.Dv NSWAPDEV , 64which is typically set to 4. 65There is no priority mechanism. 66.Pp 67The 68.Nm swapon 69utility adds the specified swap devices to the system. 70If the 71.Fl a 72option is used, all swap devices in 73.Pa /etc/fstab 74will be added, unless their 75.Dq noauto 76option is also set. 77If the 78.Fl q 79option is used informational messages will not be 80written to standard output when a swap device is added. 81If the 82.Fl e 83option is used, the device will be trimmed if 84it supports trim and the trim_enabled sysctl is on. 85.Pp 86The 87.Nm swapoff 88utility removes the specified swap devices from the system. 89If the 90.Fl a 91option is used, all swap devices in 92.Pa /etc/fstab 93will be removed, unless their 94.Dq noauto 95option is also set. 96If the 97.Fl q 98option is used informational messages will not be 99written to standard output when a swap device is removed. 100Note that 101.Nm swapoff 102will fail and refuse to remove a swap device if there is insufficient 103VM (memory + remaining swap devices) to run the system. 104The 105.Nm swapoff 106utility 107must move swapped pages out of the device being removed which could 108lead to high system loads for a period of time, depending on how 109much data has been swapped out to that device. 110.Pp 111The 112.Nm swapctl 113utility exists primarily for those familiar with other 114.Bx Ns s 115and may be 116used to add, remove, or list swap devices. 117Note that the 118.Fl a 119option is used differently in 120.Nm swapctl 121and indicates that a specific list of devices should be added. 122The 123.Fl d 124option indicates that a specific list should be removed. 125The 126.Fl A 127and 128.Fl U 129options to 130.Nm swapctl 131operate on all swap entries in 132.Pa /etc/fstab 133which do not have their 134.Dq noauto 135option set. 136.Pp 137Swap information can be generated using the 138.Xr swapinfo 8 139utility, 140.Nm pstat 141.Fl s , 142or 143.Nm swapctl 144.Fl l . 145The 146.Nm swapctl 147utility has the following options for listing swap: 148.Bl -tag -width indent 149.It Fl h 150Output values in human-readable form. 151.It Fl g 152Output values in gigabytes. 153.It Fl k 154Output values in kilobytes. 155.It Fl m 156Output values in megabytes. 157.It Fl l 158List the devices making up system swap. 159.It Fl s 160Print a summary line for system swap. 161.It Fl e 162Attempts to Trim the device if -[Aa] 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