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: src/sbin/swapon/swapon.8,v 1.15.2.2 2001/12/14 15:17:56 ru Exp $ 30.\" 31.Dd September 7, 2010 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 Fl acEiq | Ar 39.Nm swapoff Fl aq | Ar 40.Nm swapctl 41.Op Fl AeghklmsU 42.Oo 43.Fl a Ar 44| 45.Fl d Ar 46.Oc 47.Sh DESCRIPTION 48The 49.Nm swapon , swapoff 50and 51.Nm swapctl 52utilities are used to control swap devices in the system. 53At boot time all swap entries in 54.Pa /etc/fstab 55are added automatically when the system goes multi-user. 56Swap devices use a fixed interleave; the maximum number of devices 57is specified by the kernel configuration option 58.Dv NSWAPDEV , 59which is typically set to 4. 60There is no priority mechanism. 61.Pp 62The 63.Nm swapon 64utility adds the specified swap devices to the system. 65If the 66.Fl a 67option is used, all swap devices in 68.Pa /etc/fstab 69will be added. 70The following options are supported: 71.Bl -tag -width indent 72.It Dq noauto 73The device is ignored and will not be added or removed with this option. 74.It Dq crypt 75Swap will be encrpted with a random key using a /dev/mapper name of 76swap-<device> , 77for example 'swap-da0s1b'. 78This will also load the dm_target_crypt module if necessary. 79.It Dq trim 80Swap will be TRIMed if the device supports it, otherwise this option 81will be ignored. 82.El 83.Pp 84If the 85.Fl q 86option is used informational messages will not be 87written to standard output when a swap device is added. 88If the 89.Fl c 90option is used, the device will be encrypted with a random 91key. 92If the 93.Fl E 94option is used, the device will be trimmed if 95it supports trim and the trim_enabled sysctl is on. 96The 97.Fl i 98option asks user confirmation before adding a swap device. 99.Pp 100The 101.Nm swapoff 102utility removes the specified swap devices from the system. 103If the 104.Fl a 105option is used, all swap devices in 106.Pa /etc/fstab 107will be removed, unless their 108.Dq noauto 109option is also set. 110If the 111.Fl c 112option is used the device is mapped to the appropriate crypto device 113and the crypto device is removed as well. 114If this option is specified in 115.Nm swapon 116then it should also be specified in 117.Nm swapoff . 118If the 119.Fl q 120option is used informational messages will not be 121written to standard output when a swap device is removed. 122Note that 123.Nm swapoff 124will fail and refuse to remove a swap device if there is insufficient 125VM (memory + remaining swap devices) to run the system. 126The 127.Nm swapoff 128utility 129must move swapped pages out of the device being removed which could 130lead to high system loads for a period of time, depending on how 131much data has been swapped out to that device. 132.Pp 133The 134.Nm swapctl 135utility exists primarily for those familiar with other 136.Bx Ns s 137and may be 138used to add, remove, or list swap devices. 139Note that the 140.Fl a 141option is used differently in 142.Nm swapctl 143and indicates that a specific list of devices should be added. 144The 145.Fl d 146option indicates that a specific list should be removed. 147The 148.Fl A 149and 150.Fl U 151options to 152.Nm swapctl 153operate on all swap entries in 154.Pa /etc/fstab 155which do not have their 156.Dq noauto 157option set. 158.Pp 159Swap information can be generated using the 160.Xr swapinfo 8 161utility, 162.Nm pstat 163.Fl s , 164or 165.Nm swapctl 166.Fl l . 167The 168.Nm swapctl 169utility has the following options for listing swap: 170.Bl -tag -width indent 171.It Fl h 172Output values in human-readable form. 173.It Fl g 174Output values in gigabytes. 175.It Fl k 176Output values in kilobytes. 177.It Fl m 178Output values in megabytes. 179.It Fl l 180List the devices making up system swap. 181.It Fl s 182Print a summary line for system swap. 183.It Fl c 184The swap is or should be crypted. 185.It Fl e , Fl E 186Attempts to Trim the device if -[Aa] is used. The lower-case version 187of this option is deprecated. 188.It Fl i 189Asks user confirmation when -a is used. 190.It Fl q 191Less noisy output. 192.Pp 193The 194.Ev BLOCKSIZE 195environment variable is used if not specifically 196overridden. 1971K blocks are used by default. 198.El 199.Sh FILES 200.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact 201.It Pa /dev/{ad,da}?s?b 202standard paging devices 203.It Pa /dev/vn?s?b 204vnode disk paging device 205.It Pa /etc/fstab 206ASCII filesystem description table 207.It Pa /etc/vntab 208ASCII vnode file table 209.El 210.Sh DIAGNOSTICS 211These utilities may fail for the reasons described in 212.Xr swapon 2 . 213.Sh SEE ALSO 214.Xr swapon 2 , 215.Xr fstab 5 , 216.Xr init 8 , 217.Xr pstat 8 , 218.Xr rc 8 , 219.Xr vnconfig 8 220.Sh HISTORY 221The 222.Nm swapon 223utility appeared in 224.Bx 4.0 . 225The 226.Nm swapoff 227and 228.Nm swapctl 229utilities appeared in 230.Fx 5.1 231and were later ported to 232.Dx 2.7 . 233