swapon(2) [freebsd man page]
SWAPON(2) BSD System Calls Manual SWAPON(2) NAME
swapon, swapoff -- control devices for interleaved paging/swapping LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <unistd.h> int swapon(const char *special); int swapoff(const char *special); DESCRIPTION
The swapon() system call makes the block device special available to the system for allocation for paging and swapping. The names of poten- tially available devices are known to the system and defined at system configuration time. The size of the swap area on special is calcu- lated at the time the device is first made available for swapping. The swapoff() system call disables paging and swapping on the given device. All associated swap metadata are deallocated, and the device is made available for other purposes. RETURN VALUES
If an error has occurred, a value of -1 is returned and errno is set to indicate the error. ERRORS
Both swapon() and swapoff() can fail if: [ENOTDIR] A component of the path prefix is not a directory. [ENAMETOOLONG] A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters. [ENOENT] The named device does not exist. [EACCES] Search permission is denied for a component of the path prefix. [ELOOP] Too many symbolic links were encountered in translating the pathname. [EPERM] The caller is not the super-user. [EFAULT] The special argument points outside the process's allocated address space. Additionally, swapon() can fail for the following reasons: [ENOTBLK] The special argument is not a block device. [EBUSY] The device specified by special has already been made available for swapping [ENXIO] The major device number of special is out of range (this indicates no device driver exists for the associated hardware). [EIO] An I/O error occurred while opening the swap device. Lastly, swapoff() can fail if: [EINVAL] The system is not currently swapping to special. [ENOMEM] Not enough virtual memory is available to safely disable paging and swapping to the given device. SEE ALSO
config(8), swapon(8), sysctl(8) HISTORY
The swapon() system call appeared in 4.0BSD. The swapoff() system call appeared in FreeBSD 5.0. BSD
October 4, 2013 BSD
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SWAPON(8) BSD System Manager's Manual SWAPON(8) NAME
swapon, swapoff, swapctl -- specify devices for paging and swapping SYNOPSIS
swapon [-F fstab] -aLq | file ... swapoff [-F fstab] -aLq | file ... swapctl [-AghklmsU] [-a file ... | -d file ...] DESCRIPTION
The swapon, swapoff and swapctl utilities are used to control swap devices in the system. At boot time all swap entries in /etc/fstab are added automatically when the system goes multi-user. Swap devices use a fixed interleave; the maximum number of devices is unlimited. There is no priority mechanism. The swapon utility adds the specified swap devices to the system. If the -a option is used, all swap devices in /etc/fstab will be added, unless their ``noauto'' or ``late'' option is also set. If the -L option is specified, swap devices with the ``late'' option will be added as well as ones with no option. If the -q option is used, informational messages will not be written to standard output when a swap device is added. The swapoff utility removes the specified swap devices from the system. If the -a option is used, all swap devices in /etc/fstab will be removed, unless their ``noauto'' or ``late'' option is also set. If the -L option is specified, swap devices with the ``late'' option will be removed as well as ones with no option. If the -q option is used, informational messages will not be written to standard output when a swap device is removed. Note that swapoff will fail and refuse to remove a swap device if there is insufficient VM (memory + remaining swap devices) to run the system. The 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. Other options supported by both swapon and swapoff are as follows: -F fstab Specify the fstab file to use. The swapctl utility exists primarily for those familiar with other BSDs and may be used to add, remove, or list swap devices. Note that the -a option is used differently in swapctl and indicates that a specific list of devices should be added. The -d option indicates that a spe- cific list should be removed. The -A and -U options to swapctl operate on all swap entries in /etc/fstab which do not have their ``noauto'' option set. Swap information can be generated using the swapinfo(8) utility, pstat -s, or swapctl -l. The swapctl utility has the following options for listing swap: -h Output values in human-readable form. -g Output values in gigabytes. -k Output values in kilobytes. -m Output values in megabytes. -l List the devices making up system swap. -s Print a summary line for system swap. The BLOCKSIZE environment variable is used if not specifically overridden. 512 byte blocks are used by default. FILES
/dev/{ada,da}?s?b standard paging devices /dev/md? memory disk devices /etc/fstab ASCII file system description table DIAGNOSTICS
These utilities may fail for the reasons described in swapon(2). SEE ALSO
swapon(2), fstab(5), init(8), mdconfig(8), pstat(8), rc(8) HISTORY
The swapon utility appeared in 4.0BSD. The swapoff and swapctl utilities appeared in FreeBSD 5.1. BSD
November 22, 2013 BSD