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 21, 2013 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 39.Oo Fl F Ar fstab 40.Oc 41.Fl aLq | Ar 42.Nm swapoff 43.Oo Fl F Ar fstab 44.Oc 45.Fl aLq | Ar 46.Nm swapctl 47.Op Fl AghklmsU 48.Oo 49.Fl a Ar 50| 51.Fl d Ar 52.Oc 53.Sh DESCRIPTION 54The 55.Nm swapon , swapoff 56and 57.Nm swapctl 58utilities are used to control swap devices in the system. 59At boot time all swap entries in 60.Pa /etc/fstab 61are added automatically when the system goes multi-user. 62Swap devices use a fixed interleave; the maximum number of devices 63is specified by the kernel configuration option 64.Dv NSWAPDEV , 65which is typically set to 4. 66There is no priority mechanism. 67.Pp 68The 69.Nm swapon 70utility adds the specified swap devices to the system. 71If the 72.Fl a 73option is used, all swap devices in 74.Pa /etc/fstab 75will be added, unless their 76.Dq noauto 77or 78.Dq late 79option is also set. 80If the 81.Fl L 82option is specified, 83swap devices with the 84.Dq late 85option will be added as well as ones with no option. 86If the 87.Fl q 88option is used, 89informational messages will not be 90written to standard output when a swap device is added. 91.Pp 92The 93.Nm swapoff 94utility removes the specified swap devices from the system. 95If the 96.Fl a 97option is used, all swap devices in 98.Pa /etc/fstab 99will be removed, unless their 100.Dq noauto 101or 102.Dq late 103option is also set. 104If the 105.Fl L 106option is specified, 107swap devices with the 108.Dq late 109option will be removed as well as ones with no option. 110If the 111.Fl q 112option is used, 113informational messages will not be 114written to standard output when a swap device is removed. 115Note that 116.Nm swapoff 117will fail and refuse to remove a swap device if there is insufficient 118VM (memory + remaining swap devices) to run the system. 119The 120.Nm swapoff 121utility 122must move swapped pages out of the device being removed which could 123lead to high system loads for a period of time, depending on how 124much data has been swapped out to that device. 125.Pp 126Other options supported by both 127.Nm swapon 128and 129.Nm swapoff 130are as follows: 131.Bl -tag -width indent 132.It Fl F Ar fstab 133Specify the 134.Pa fstab 135file to use. 136.El 137.Pp 138The 139.Nm swapctl 140utility exists primarily for those familiar with other 141.Bx Ns s 142and may be 143used to add, remove, or list swap devices. 144Note that the 145.Fl a 146option is used differently in 147.Nm swapctl 148and indicates that a specific list of devices should be added. 149The 150.Fl d 151option indicates that a specific list should be removed. 152The 153.Fl A 154and 155.Fl U 156options to 157.Nm swapctl 158operate on all swap entries in 159.Pa /etc/fstab 160which do not have their 161.Dq noauto 162option set. 163.Pp 164Swap information can be generated using the 165.Xr swapinfo 8 166utility, 167.Nm pstat 168.Fl s , 169or 170.Nm swapctl 171.Fl l . 172The 173.Nm swapctl 174utility has the following options for listing swap: 175.Bl -tag -width indent 176.It Fl h 177Output values in human-readable form. 178.It Fl g 179Output values in gigabytes. 180.It Fl k 181Output values in kilobytes. 182.It Fl m 183Output values in megabytes. 184.It Fl l 185List the devices making up system swap. 186.It Fl s 187Print a summary line for system swap. 188.Pp 189The 190.Ev BLOCKSIZE 191environment variable is used if not specifically 192overridden. 193512 byte blocks are used by default. 194.El 195.Sh FILES 196.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact 197.It Pa /dev/{ad,da}?s?b 198standard paging devices 199.It Pa /dev/md? 200memory disk devices 201.It Pa /etc/fstab 202.Tn ASCII 203file system description table 204.El 205.Sh DIAGNOSTICS 206These utilities may fail for the reasons described in 207.Xr swapon 2 . 208.Sh SEE ALSO 209.Xr swapon 2 , 210.Xr fstab 5 , 211.Xr init 8 , 212.Xr mdconfig 8 , 213.Xr pstat 8 , 214.Xr rc 8 215.Sh HISTORY 216The 217.Nm swapon 218utility appeared in 219.Bx 4.0 . 220The 221.Nm swapoff 222and 223.Nm swapctl 224utilities appeared in 225.Fx 5.1 . 226