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.2 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/sys/swapon.2,v 1.6.2.6 2001/12/14 18:34:01 ru Exp $ 30.\" $DragonFly: src/lib/libc/sys/swapon.2,v 1.3 2006/02/17 19:35:06 swildner Exp $ 31.\" 32.Dd September 7, 2010 33.Dt SWAPON 2 34.Os 35.Sh NAME 36.Nm swapon , swapoff 37.Nd control devices for interleaved paging/swapping 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In unistd.h 42.Ft int 43.Fn swapon "const char *special" 44.Ft int 45.Fn swapoff "const char *special" 46.Sh DESCRIPTION 47The 48.Fn swapon 49system call 50makes the block device 51.Fa special 52available to the system for 53allocation for paging and swapping. 54The names of potentially 55available devices are known to the system and defined at system 56configuration time. 57The size of the swap area on 58.Fa special 59is calculated at the time the device is first made available 60for swapping. 61.Pp 62The 63.Fn swapoff 64system call disables paging and swapping on the given device. 65All associated swap metadata are deallocated, and the device 66is made available for other purposes. 67.Sh RETURN VALUES 68If an error has occurred, a value of -1 is returned and 69.Va errno 70is set to indicate the error. 71.Sh ERRORS 72Both 73.Fn swapon 74and 75.Fn swapoff 76can fail if: 77.Bl -tag -width Er 78.It Bq Er ENOTDIR 79A component of the path prefix is not a directory. 80.It Bq Er ENAMETOOLONG 81A component of a pathname exceeded 255 characters, 82or an entire path name exceeded 1023 characters. 83.It Bq Er ENOENT 84The named device does not exist. 85.It Bq Er EACCES 86Search permission is denied for a component of the path prefix. 87.It Bq Er ELOOP 88Too many symbolic links were encountered in translating the pathname. 89.It Bq Er EPERM 90The caller is not the super-user. 91.It Bq Er EFAULT 92The 93.Fa special 94argument 95points outside the process's allocated address space. 96.El 97.Pp 98Additionally, 99.Fn swapon 100can fail for the following reasons: 101.Bl -tag -width Er 102.It Bq Er EINVAL 103The system has reached the boot-time limit on the number of 104swap devices, 105.Va vm.nswapdev . 106.It Bq Er ENOTBLK 107The 108.Fa special 109argument 110is not a block device. 111.It Bq Er EBUSY 112The device specified by 113.Fa special 114has already 115been made available for swapping 116.It Bq Er ENXIO 117The major device number of 118.Fa special 119is out of range (this indicates no device driver exists 120for the associated hardware). 121.It Bq Er EIO 122An I/O error occurred while opening the swap device. 123.El 124.Pp 125Lastly, 126.Fn swapoff 127can fail if: 128.Bl -tag -width Er 129.It Bq Er EINVAL 130The system is not currently swapping to 131.Fa special . 132.It Bq Er ENOMEM 133Not enough virtual memory is available to safely disable 134paging and swapping to the given device. 135.El 136.Sh SEE ALSO 137.Xr config 8 , 138.Xr swapon 8 , 139.Xr sysctl 8 140.Sh HISTORY 141The 142.Fn swapon 143system call appeared in 144.Bx 4.0 . 145The 146.Fn swapoff 147system call appeared in 148.Fx 5.0 149and was later ported to 150.Dx 2.7 . 151