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. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)swapon.8 8.1 (Berkeley) 6/5/93 33.\" $FreeBSD: src/sbin/swapon/swapon.8,v 1.15.2.2 2001/12/14 15:17:56 ru Exp $ 34.\" $DragonFly: src/sbin/swapon/swapon.8,v 1.4 2007/08/10 18:28:27 swildner Exp $ 35.\" 36.Dd September 7, 2010 37.Dt SWAPON 8 38.Os 39.Sh NAME 40.Nm swapon , swapoff , swapctl 41.Nd "specify devices for paging and swapping" 42.Sh SYNOPSIS 43.Nm swapon Fl aq | Ar 44.Nm swapoff Fl aq | Ar 45.Nm swapctl 46.Op Fl AghklmsU 47.Oo 48.Fl a Ar 49| 50.Fl d Ar 51.Oc 52.Sh DESCRIPTION 53The 54.Nm swapon , swapoff 55and 56.Nm swapctl 57utilities are used to control swap devices in the system. 58At boot time all swap entries in 59.Pa /etc/fstab 60are added automatically when the system goes multi-user. 61Swap devices use a fixed interleave; the maximum number of devices 62is specified by the kernel configuration option 63.Dv NSWAPDEV , 64which is typically set to 4. 65There is no priority mechanism. 66.Pp 67The 68.Nm swapon 69utility adds the specified swap devices to the system. 70If the 71.Fl a 72option is used, all swap devices in 73.Pa /etc/fstab 74will be added, unless their 75.Dq noauto 76option is also set. 77If the 78.Fl q 79option is used informational messages will not be 80written to standard output when a swap device is added. 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.Pp 158The 159.Ev BLOCKSIZE 160environment variable is used if not specifically 161overridden. 1621K blocks are used by default. 163.El 164.Sh FILES 165.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact 166.It Pa /dev/{ad,da}?s?b 167standard paging devices 168.It Pa /dev/vn?s?b 169vnode disk paging device 170.It Pa /etc/fstab 171ASCII filesystem description table 172.It Pa /etc/vntab 173ASCII vnode file table 174.El 175.Sh DIAGNOSTICS 176These utilities may fail for the reasons described in 177.Xr swapon 2 . 178.Sh SEE ALSO 179.Xr swapon 2 , 180.Xr fstab 5 , 181.Xr init 8 , 182.Xr pstat 8 , 183.Xr rc 8 , 184.Xr vnconfig 8 185.Sh HISTORY 186The 187.Nm swapon 188utility appeared in 189.Bx 4.0 . 190The 191.Nm swapoff 192and 193.Nm swapctl 194utilities appeared in 195.Fx 5.1 196and were later ported to 197.Dx 2.7 . 198