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SWAPON(2) FreeBSD 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, u_int flags);
DESCRIPTION
The swapon() system call makes the block device special available to the
system for allocation for paging and swapping. The names of potentially
available devices are known to the system and defined at system
configuration time. The size of the swap area on special is calculated
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.
The special argument points to the name of the device or file used for
swapping. flags argument takes the following flags:
SWAPOFF_FORCE Overrides a very conservative check that prevents swapoff
if the total amount of free memory and remaining swap
devices space might be unsufficient for the system to
continue operating.
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
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.
[EINTEGRITY] Corrupted data was detected while reading from the
file system to open 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.
FreeBSD 14.0-RELEASE-p11 December 8, 2021 FreeBSD 14.0-RELEASE-p11