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 October 21, 2016 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 unlimited. 64There is no priority mechanism. 65.Pp 66The 67.Nm swapon 68utility adds the specified swap devices to the system. 69If the 70.Fl a 71option is used, all swap devices in 72.Pa /etc/fstab 73will be added, unless their 74.Dq noauto 75or 76.Dq late 77option is also set. 78If the 79.Fl L 80option is specified, 81swap devices with the 82.Dq late 83option will be added as well as ones with no option. 84If the 85.Fl q 86option is used, 87informational messages will not be 88written to standard output when a swap device is added. 89.Pp 90The 91.Nm swapoff 92utility removes the specified swap devices from the system. 93If the 94.Fl a 95option is used, all swap devices in 96.Pa /etc/fstab 97will be removed, unless their 98.Dq noauto 99option is also set. 100If the 101.Fl L 102option is specified, 103only swap devices with the 104.Dq late 105option will be removed. 106If the 107.Fl q 108option is used, 109informational messages will not be 110written to standard output when a swap device is removed. 111Note that 112.Nm swapoff 113will fail and refuse to remove a swap device if there is insufficient 114VM (memory + remaining swap devices) to run the system. 115The 116.Nm swapoff 117utility 118must move swapped pages out of the device being removed which could 119lead to high system loads for a period of time, depending on how 120much data has been swapped out to that device. 121.Pp 122Other options supported by both 123.Nm swapon 124and 125.Nm swapoff 126are as follows: 127.Bl -tag -width indent 128.It Fl F Ar fstab 129Specify the 130.Pa fstab 131file to use. 132.El 133.Pp 134The 135.Nm swapctl 136utility exists primarily for those familiar with other 137.Bx Ns s 138and may be 139used to add, remove, or list swap devices. 140Note that the 141.Fl a 142option is used differently in 143.Nm swapctl 144and indicates that a specific list of devices should be added. 145The 146.Fl d 147option indicates that a specific list should be removed. 148The 149.Fl A 150and 151.Fl U 152options to 153.Nm swapctl 154operate on all swap entries in 155.Pa /etc/fstab 156which do not have their 157.Dq noauto 158option set. 159.Pp 160Swap information can be generated using the 161.Xr swapinfo 8 162utility, 163.Nm pstat 164.Fl s , 165or 166.Nm swapctl 167.Fl l . 168The 169.Nm swapctl 170utility has the following options for listing swap: 171.Bl -tag -width indent 172.It Fl h 173Output values in human-readable form. 174.It Fl g 175Output values in gigabytes. 176.It Fl k 177Output values in kilobytes. 178.It Fl m 179Output values in megabytes. 180.It Fl l 181List the devices making up system swap. 182.It Fl s 183Print a summary line for system swap. 184.Pp 185The 186.Ev BLOCKSIZE 187environment variable is used if not specifically 188overridden. 189512 byte blocks are used by default. 190.El 191.Sh FILES 192.Bl -tag -width ".Pa /dev/{ada,da}?s?b" -compact 193.It Pa /dev/{ada,da}?s?b 194standard paging devices 195.It Pa /dev/md? 196memory disk devices 197.It Pa /etc/fstab 198.Tn ASCII 199file system description table 200.El 201.Sh DIAGNOSTICS 202These utilities may fail for the reasons described in 203.Xr swapon 2 . 204.Sh SEE ALSO 205.Xr swapon 2 , 206.Xr fstab 5 , 207.Xr init 8 , 208.Xr mdconfig 8 , 209.Xr pstat 8 , 210.Xr rc 8 211.Sh HISTORY 212The 213.Nm swapon 214utility appeared in 215.Bx 4.0 . 216The 217.Nm swapoff 218and 219.Nm swapctl 220utilities appeared in 221.Fx 5.1 . 222