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
Theswapon, 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” option is also set. If the
-L option is specified, only swap devices with the
“late” option will be removed. 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:
-Ffstab- 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 specific 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
BLOCKSIZEenvironment 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
HISTORY
The swapon utility appeared in
4.0BSD. The swapoff and
swapctl utilities appeared in
FreeBSD 5.1.