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.\" $FreeBSD$ 34.\" 35.Dd December 28, 2002 36.Dt SWAPON 8 37.Os 38.Sh NAME 39.Nm swapon , swapoff , swapctl 40.Nd "specify devices for paging and swapping" 41.Sh SYNOPSIS 42.Nm swapon Ar 43.Nm swapon Fl a 44.Nm swapoff Ar 45.Nm swapoff Fl a 46.Nm swapctl 47.Op Fl AhklsU 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 specified by the kernel configuration option 64.Dv NSWAPDEV , 65which is typically set to 4. 66There is no priority mechanism. 67.Pp 68The 69.Nm swapon 70utility adds the specified swap devices to the system. 71If the 72.Fl a 73option is used, all swap devices in 74.Pa /etc/fstab 75will be added, unless their 76.Dq noauto 77option is also set. 78.Pp 79The 80.Nm swapoff 81utility removes the specified swap devices from the system. 82If the 83.Fl a 84option is used, all swap devices in 85.Pa /etc/fstab 86will be removed, unless their 87.Dq noauto 88option is also set. 89Note that 90.Nm swapoff 91will fail and refuse to remove a swap device if there is insufficient 92VM (memory + remaining swap devices) to run the system. 93The 94.Nm swapoff 95utility 96must move swapped pages out of the device being removed which could 97lead to high system loads for a period of time, depending on how 98much data has been swapped out to that device. 99.Pp 100The 101.Nm swapctl 102utility exists primarily for those familiar with other 103.Bx Ns s 104and may be 105used to add, remove, or list swap devices. 106Note that the 107.Fl a 108option is used differently in 109.Nm swapctl 110and indicates that a specific list of devices should be added. 111The 112.Fl d 113option indicates that a specific list should be removed. 114The 115.Fl A 116and 117.Fl U 118options to 119.Nm swapctl 120operate on all swap entries in 121.Pa /etc/fstab 122which do not have their 123.Dq noauto 124option set. 125.Pp 126Swap information can be generated using the 127.Xr swapinfo 8 128utility, 129.Nm pstat 130.Fl s , 131or 132.Nm swapctl 133.Fl l . 134The 135.Nm swapctl 136utility has the following options for listing swap: 137.Bl -tag -width indent 138.It Fl h 139Output values in megabytes. 140.It Fl k 141Output values in kilobytes. 142.It Fl l 143List the devices making up system swap. 144.It Fl s 145Print a summary line for system swap. 146.Pp 147The 148.Ev BLOCKSIZE 149environment variable is used if not specifically 150overridden. 151512 byte blocks are used by default. 152.El 153.Sh DIAGNOSTICS 154These utilities may fail for the reasons described in 155.Xr swapon 2 . 156.Sh SEE ALSO 157.Xr swapon 2 , 158.Xr fstab 5 , 159.Xr init 8 , 160.Xr mdconfig 8 , 161.Xr pstat 8 , 162.Xr rc 8 163.Sh FILES 164.Bl -tag -width ".Pa /dev/{ad,da}?s?b" -compact 165.It Pa /dev/{ad,da}?s?b 166standard paging devices 167.It Pa /dev/md? 168memory disk devices 169.It Pa /etc/fstab 170.Tn ASCII 171file system description table 172.El 173.Sh HISTORY 174The 175.Nm swapon 176utility appeared in 177.Bx 4.0 . 178The 179.Nm swapoff 180and 181.Nm swapctl 182utilities appeared in 183.Fx 5.1 . 184