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 2, 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 q 102option is used, 103informational messages will not be 104written to standard output when a swap device is removed. 105Note that 106.Nm swapoff 107will fail and refuse to remove a swap device if there is insufficient 108VM (memory + remaining swap devices) to run the system. 109The 110.Nm swapoff 111utility 112must move swapped pages out of the device being removed which could 113lead to high system loads for a period of time, depending on how 114much data has been swapped out to that device. 115.Pp 116Other options supported by both 117.Nm swapon 118and 119.Nm swapoff 120are as follows: 121.Bl -tag -width indent 122.It Fl F Ar fstab 123Specify the 124.Pa fstab 125file to use. 126.El 127.Pp 128The 129.Nm swapctl 130utility exists primarily for those familiar with other 131.Bx Ns s 132and may be 133used to add, remove, or list swap devices. 134Note that the 135.Fl a 136option is used differently in 137.Nm swapctl 138and indicates that a specific list of devices should be added. 139The 140.Fl d 141option indicates that a specific list should be removed. 142The 143.Fl A 144and 145.Fl U 146options to 147.Nm swapctl 148operate on all swap entries in 149.Pa /etc/fstab 150which do not have their 151.Dq noauto 152option set. 153.Pp 154Swap information can be generated using the 155.Xr swapinfo 8 156utility, 157.Nm pstat 158.Fl s , 159or 160.Nm swapctl 161.Fl l . 162The 163.Nm swapctl 164utility has the following options for listing swap: 165.Bl -tag -width indent 166.It Fl h 167Output values in human-readable form. 168.It Fl g 169Output values in gigabytes. 170.It Fl k 171Output values in kilobytes. 172.It Fl m 173Output values in megabytes. 174.It Fl l 175List the devices making up system swap. 176.It Fl s 177Print a summary line for system swap. 178.Pp 179The 180.Ev BLOCKSIZE 181environment variable is used if not specifically 182overridden. 183512 byte blocks are used by default. 184.El 185.Sh FILES 186.Bl -tag -width ".Pa /dev/{ada,da}?s?b" -compact 187.It Pa /dev/{ada,da}?s?b 188standard paging devices 189.It Pa /dev/md? 190memory disk devices 191.It Pa /etc/fstab 192.Tn ASCII 193file system description table 194.El 195.Sh DIAGNOSTICS 196These utilities may fail for the reasons described in 197.Xr swapon 2 . 198.Sh SEE ALSO 199.Xr swapon 2 , 200.Xr fstab 5 , 201.Xr init 8 , 202.Xr mdconfig 8 , 203.Xr pstat 8 , 204.Xr rc 8 205.Sh HISTORY 206The 207.Nm swapon 208utility appeared in 209.Bx 4.0 . 210The 211.Nm swapoff 212and 213.Nm swapctl 214utilities appeared in 215.Fx 5.1 . 216