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.Dd December 8, 2021 29.Dt SWAPON 2 30.Os 31.Sh NAME 32.Nm swapon , swapoff 33.Nd control devices for interleaved paging/swapping 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In vm/vm_param.h 38.In vm/swap_pager.h 39.Pp 40.In unistd.h 41.Ft int 42.Fn swapon "const char *special" 43.Ft int 44.Fn swapoff "const char *special" "u_int flags" 45.Sh DESCRIPTION 46The 47.Fn swapon 48system call 49makes the block device 50.Fa special 51available to the system for 52allocation for paging and swapping. 53The names of potentially 54available devices are known to the system and defined at system 55configuration time. 56The size of the swap area on 57.Fa special 58is calculated at the time the device is first made available 59for swapping. 60.Pp 61The 62.Fn swapoff 63system call disables paging and swapping on the given device. 64All associated swap metadata are deallocated, and the device 65is made available for other purposes. 66.Pp 67The 68.Fa special 69argument points to the name of the device or file used for swapping. 70The 71.Va flags 72argument takes the following flags: 73.Bl -tag -width SWAPOFF_FORCE 74.It Dv SWAPOFF_FORCE 75Overrides a very conservative check that prevents swapoff 76if the total amount of free memory and remaining swap 77devices space might be unsufficient for the system to continue 78operating. 79.El 80.Sh RETURN VALUES 81If an error has occurred, a value of -1 is returned and 82.Va errno 83is set to indicate the error. 84.Sh ERRORS 85Both 86.Fn swapon 87and 88.Fn swapoff 89can fail if: 90.Bl -tag -width Er 91.It Bq Er ENOTDIR 92A component of the path prefix is not a directory. 93.It Bq Er ENAMETOOLONG 94A component of a pathname exceeded 255 characters, 95or an entire path name exceeded 1023 characters. 96.It Bq Er ENOENT 97The named device does not exist. 98.It Bq Er EACCES 99Search permission is denied for a component of the path prefix. 100.It Bq Er ELOOP 101Too many symbolic links were encountered in translating the pathname. 102.It Bq Er EPERM 103The caller is not the super-user. 104.It Bq Er EFAULT 105The 106.Fa special 107argument 108points outside the process's allocated address space. 109.El 110.Pp 111Additionally, 112.Fn swapon 113can fail for the following reasons: 114.Bl -tag -width Er 115.It Bq Er ENOTBLK 116The 117.Fa special 118argument 119is not a block device. 120.It Bq Er EBUSY 121The device specified by 122.Fa special 123has already 124been made available for swapping 125.It Bq Er ENXIO 126The major device number of 127.Fa special 128is out of range (this indicates no device driver exists 129for the associated hardware). 130.It Bq Er EIO 131An I/O error occurred while opening the swap device. 132.It Bq Er EINTEGRITY 133Corrupted data was detected while reading from the file system to open the 134swap device. 135.El 136.Pp 137Lastly, 138.Fn swapoff 139can fail if: 140.Bl -tag -width Er 141.It Bq Er EINVAL 142The system is not currently swapping to 143.Fa special . 144.It Bq Er ENOMEM 145Not enough virtual memory is available to safely disable 146paging and swapping to the given device. 147.El 148.Sh SEE ALSO 149.Xr config 8 , 150.Xr swapon 8 , 151.Xr sysctl 8 152.Sh HISTORY 153The 154.Fn swapon 155system call appeared in 156.Bx 4.0 . 157The 158.Fn swapoff 159system call appeared in 160.Fx 5.1 . 161