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.\" $FreeBSD$ 30.\" 31.Dd June 21, 2019 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 | E 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. 89The 90.Fl E 91option causes each of following devices to receive a 92.Dv BIO_DELETE 93command to mark all blocks as unused. 94.Pp 95The 96.Nm swapoff 97utility removes the specified swap devices from the system. 98If the 99.Fl a 100option is used, all swap devices in 101.Pa /etc/fstab 102will be removed, unless their 103.Dq noauto 104option is also set. 105If the 106.Fl L 107option is specified, 108only swap devices with the 109.Dq late 110option will be removed. 111If the 112.Fl q 113option is used, 114informational messages will not be 115written to standard output when a swap device is removed. 116Note that 117.Nm swapoff 118will fail and refuse to remove a swap device if there is insufficient 119VM (memory + remaining swap devices) to run the system. 120The 121.Nm swapoff 122utility 123must move swapped pages out of the device being removed which could 124lead to high system loads for a period of time, depending on how 125much data has been swapped out to that device. 126.Pp 127Other options supported by both 128.Nm swapon 129and 130.Nm swapoff 131are as follows: 132.Bl -tag -width indent 133.It Fl F Ar fstab 134Specify the 135.Pa fstab 136file to use. 137.El 138.Pp 139The 140.Nm swapctl 141utility exists primarily for those familiar with other 142.Bx Ns s 143and may be 144used to add, remove, or list swap devices. 145Note that the 146.Fl a 147option is used differently in 148.Nm swapctl 149and indicates that a specific list of devices should be added. 150The 151.Fl d 152option indicates that a specific list should be removed. 153The 154.Fl A 155and 156.Fl U 157options to 158.Nm swapctl 159operate on all swap entries in 160.Pa /etc/fstab 161which do not have their 162.Dq noauto 163option set. 164.Pp 165Swap information can be generated using the 166.Xr swapinfo 8 167utility, 168.Nm pstat 169.Fl s , 170or 171.Nm swapctl 172.Fl l . 173The 174.Nm swapctl 175utility has the following options for listing swap: 176.Bl -tag -width indent 177.It Fl h 178Output values in human-readable form. 179.It Fl g 180Output values in gigabytes. 181.It Fl k 182Output values in kilobytes. 183.It Fl m 184Output values in megabytes. 185.It Fl l 186List the devices making up system swap. 187.It Fl s 188Print a summary line for system swap. 189.Pp 190The 191.Ev BLOCKSIZE 192environment variable is used if not specifically 193overridden. 194512 byte blocks are used by default. 195.El 196.Sh FILES 197.Bl -tag -width ".Pa /dev/{ada,da}?s?b" -compact 198.It Pa /dev/{ada,da}?s?b 199standard paging devices 200.It Pa /dev/md? 201memory disk devices 202.It Pa /etc/fstab 203.Tn ASCII 204file system description table 205.El 206.Sh DIAGNOSTICS 207These utilities may fail for the reasons described in 208.Xr swapon 2 . 209.Sh SEE ALSO 210.Xr swapon 2 , 211.Xr fstab 5 , 212.Xr init 8 , 213.Xr mdconfig 8 , 214.Xr pstat 8 , 215.Xr rc 8 216.Sh HISTORY 217The 218.Nm swapon 219utility appeared in 220.Bx 4.0 . 221The 222.Nm swapoff 223and 224.Nm swapctl 225utilities appeared in 226.Fx 5.1 . 227