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.\" $DragonFly: src/sbin/swapon/swapon.8,v 1.4 2007/08/10 18:28:27 swildner Exp $ 31.\" 32.Dd September 7, 2010 33.Dt SWAPON 8 34.Os 35.Sh NAME 36.Nm swapon , swapoff , swapctl 37.Nd "specify devices for paging and swapping" 38.Sh SYNOPSIS 39.Nm swapon Fl aeq | Ar 40.Nm swapoff Fl aq | Ar 41.Nm swapctl 42.Op Fl AeghklmsU 43.Oo 44.Fl a Ar 45| 46.Fl d Ar 47.Oc 48.Sh DESCRIPTION 49The 50.Nm swapon , swapoff 51and 52.Nm swapctl 53utilities are used to control swap devices in the system. 54At boot time all swap entries in 55.Pa /etc/fstab 56are added automatically when the system goes multi-user. 57Swap devices use a fixed interleave; the maximum number of devices 58is specified by the kernel configuration option 59.Dv NSWAPDEV , 60which is typically set to 4. 61There is no priority mechanism. 62.Pp 63The 64.Nm swapon 65utility adds the specified swap devices to the system. 66If the 67.Fl a 68option is used, all swap devices in 69.Pa /etc/fstab 70will be added, unless their 71.Dq noauto 72option is also set. 73If the 74.Fl q 75option is used informational messages will not be 76written to standard output when a swap device is added. 77If the 78.Fl e 79option is used, the device will be trimmed if 80it supports trim and the trim_enabled sysctl is on. 81.Pp 82The 83.Nm swapoff 84utility removes the specified swap devices from the system. 85If the 86.Fl a 87option is used, all swap devices in 88.Pa /etc/fstab 89will be removed, unless their 90.Dq noauto 91option is also set. 92If the 93.Fl q 94option is used informational messages will not be 95written to standard output when a swap device is removed. 96Note that 97.Nm swapoff 98will fail and refuse to remove a swap device if there is insufficient 99VM (memory + remaining swap devices) to run the system. 100The 101.Nm swapoff 102utility 103must move swapped pages out of the device being removed which could 104lead to high system loads for a period of time, depending on how 105much data has been swapped out to that device. 106.Pp 107The 108.Nm swapctl 109utility exists primarily for those familiar with other 110.Bx Ns s 111and may be 112used to add, remove, or list swap devices. 113Note that the 114.Fl a 115option is used differently in 116.Nm swapctl 117and indicates that a specific list of devices should be added. 118The 119.Fl d 120option indicates that a specific list should be removed. 121The 122.Fl A 123and 124.Fl U 125options to 126.Nm swapctl 127operate on all swap entries in 128.Pa /etc/fstab 129which do not have their 130.Dq noauto 131option set. 132.Pp 133Swap information can be generated using the 134.Xr swapinfo 8 135utility, 136.Nm pstat 137.Fl s , 138or 139.Nm swapctl 140.Fl l . 141The 142.Nm swapctl 143utility has the following options for listing swap: 144.Bl -tag -width indent 145.It Fl h 146Output values in human-readable form. 147.It Fl g 148Output values in gigabytes. 149.It Fl k 150Output values in kilobytes. 151.It Fl m 152Output values in megabytes. 153.It Fl l 154List the devices making up system swap. 155.It Fl s 156Print a summary line for system swap. 157.It Fl e 158Attempts to Trim the device if -[Aa] is used. 159.Pp 160The 161.Ev BLOCKSIZE 162environment variable is used if not specifically 163overridden. 1641K blocks are used by default. 165.El 166.Sh FILES 167.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact 168.It Pa /dev/{ad,da}?s?b 169standard paging devices 170.It Pa /dev/vn?s?b 171vnode disk paging device 172.It Pa /etc/fstab 173ASCII filesystem description table 174.It Pa /etc/vntab 175ASCII vnode file table 176.El 177.Sh DIAGNOSTICS 178These utilities may fail for the reasons described in 179.Xr swapon 2 . 180.Sh SEE ALSO 181.Xr swapon 2 , 182.Xr fstab 5 , 183.Xr init 8 , 184.Xr pstat 8 , 185.Xr rc 8 , 186.Xr vnconfig 8 187.Sh HISTORY 188The 189.Nm swapon 190utility appeared in 191.Bx 4.0 . 192The 193.Nm swapoff 194and 195.Nm swapctl 196utilities appeared in 197.Fx 5.1 198and were later ported to 199.Dx 2.7 . 200