.\" Copyright (c) 1980, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)swapon.8 8.1 (Berkeley) 6/5/93 .\" $FreeBSD: src/sbin/swapon/swapon.8,v 1.15.2.2 2001/12/14 15:17:56 ru Exp $ .\" .Dd September 7, 2010 .Dt SWAPON 8 .Os .Sh NAME .Nm swapon , swapoff , swapctl .Nd "specify devices for paging and swapping" .Sh SYNOPSIS .Nm swapon Fl acEiq | Ar .Nm swapoff Fl aq | Ar .Nm swapctl .Op Fl AeghklmsU .Oo .Fl a Ar | .Fl d Ar .Oc .Sh DESCRIPTION The .Nm swapon , swapoff and .Nm swapctl utilities are used to control swap devices in the system. At boot time all swap entries in .Pa /etc/fstab are added automatically when the system goes multi-user. Swap devices use a fixed interleave; the maximum number of devices is specified by the kernel configuration option .Dv NSWAPDEV , which is typically set to 4. There is no priority mechanism. .Pp The .Nm swapon utility adds the specified swap devices to the system. If the .Fl a option is used, all swap devices in .Pa /etc/fstab will be added. The following options are supported: .Bl -tag -width indent .It Dq noauto The device is ignored and will not be added or removed with this option. .It Dq crypt Swap will be encrpted with a random key using a /dev/mapper name of swap- , for example 'swap-da0s1b'. This will also load the dm_target_crypt module if necessary. .It Dq trim Swap will be TRIMed if the device supports it, otherwise this option will be ignored. .El .Pp If the .Fl q option is used informational messages will not be written to standard output when a swap device is added. If the .Fl c option is used, the device will be encrypted with a random key. If the .Fl E option is used, the device will be trimmed if it supports trim and the trim_enabled sysctl is on. The .Fl i option asks user confirmation before adding a swap device. .Pp The .Nm swapoff utility removes the specified swap devices from the system. If the .Fl a option is used, all swap devices in .Pa /etc/fstab will be removed, unless their .Dq noauto option is also set. If the .Fl c option is used the device is mapped to the appropriate crypto device and the crypto device is removed as well. If this option is specified in .Nm swapon then it should also be specified in .Nm swapoff . If the .Fl q option is used informational messages will not be written to standard output when a swap device is removed. Note that .Nm swapoff will fail and refuse to remove a swap device if there is insufficient VM (memory + remaining swap devices) to run the system. The .Nm swapoff utility must move swapped pages out of the device being removed which could lead to high system loads for a period of time, depending on how much data has been swapped out to that device. .Pp The .Nm swapctl utility exists primarily for those familiar with other .Bx Ns s and may be used to add, remove, or list swap devices. Note that the .Fl a option is used differently in .Nm swapctl and indicates that a specific list of devices should be added. The .Fl d option indicates that a specific list should be removed. The .Fl A and .Fl U options to .Nm swapctl operate on all swap entries in .Pa /etc/fstab which do not have their .Dq noauto option set. .Pp Swap information can be generated using the .Xr swapinfo 8 utility, .Nm pstat .Fl s , or .Nm swapctl .Fl l . The .Nm swapctl utility has the following options for listing swap: .Bl -tag -width indent .It Fl h Output values in human-readable form. .It Fl g Output values in gigabytes. .It Fl k Output values in kilobytes. .It Fl m Output values in megabytes. .It Fl l List the devices making up system swap. .It Fl s Print a summary line for system swap. .It Fl c The swap is or should be crypted. .It Fl e , Fl E Attempts to Trim the device if -[Aa] is used. The lower-case version of this option is deprecated. .It Fl i Asks user confirmation when -a is used. .It Fl q Less noisy output. .Pp The .Ev BLOCKSIZE environment variable is used if not specifically overridden. 1K blocks are used by default. .El .Sh FILES .Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact .It Pa /dev/{ad,da}?s?b standard paging devices .It Pa /dev/vn?s?b vnode disk paging device .It Pa /etc/fstab ASCII filesystem description table .It Pa /etc/vntab ASCII vnode file table .El .Sh DIAGNOSTICS These utilities may fail for the reasons described in .Xr swapon 2 . .Sh SEE ALSO .Xr swapon 2 , .Xr fstab 5 , .Xr init 8 , .Xr pstat 8 , .Xr rc 8 , .Xr vnconfig 8 .Sh HISTORY The .Nm swapon utility appeared in .Bx 4.0 . The .Nm swapoff and .Nm swapctl utilities appeared in .Fx 5.1 and were later ported to .Dx 2.7 .