SWAPCTL(8) | System Manager's Manual | SWAPCTL(8) |
swapctl
, swapon
— system swap management tool
swapctl |
-A [-p
priority] [-t
blk | noblk ] |
swapctl |
-a [-p
priority] path |
swapctl |
-c -p
priority path |
swapctl |
-d path |
swapctl |
[[-l ] | -s ]
[-k ] |
swapon |
-a | path |
The swapctl
program adds, removes, lists
and prioritizes swap devices and files for the system. The
swapon
program acts the same as
swapctl -a
, except if swapon
itself is called with -a
, in which case it acts as
swapctl -A
.
The options are as follows:
-A
swapctl
to read the
/etc/fstab file for devices and files with an
“sw” type, and adds all these entries as swap devices. If no
swap devices are configured, swapctl
will exit
with an error code.-a
-a
option requires that a
path also be in the argument list. The
path is added to the kernel's list of swap devices
using the swapctl(2) system call. When
using the swapon
form of this command, the
-a
option is treated the same as the
-A
option, for backwards compatibility.-c
-c
option changes the priority of the listed
swap device or file.-d
path-d
option removes the listed
path from the kernel's list of swap devices or
files.-k
-k
option uses 1024 byte blocks instead of the
default 512 byte.-l
-l
option lists the current swap devices and
files, and their usage statistics.-p
priority-p
option sets the priority of swap devices or
files to the priority argument.-s
-s
option displays a single line summary of
current swap statistics.-t
blk
|
noblk
-A
option.
The -t
option allows the type of device to add to
be specified. An argument of blk
causes all block
devices in /etc/fstab to be added. An argument of
noblk
causes all non-block devices in
/etc/fstab to be added. This option is useful in
early system startup, where swapping may be needed before all file systems
are available, such as during disk checks of large file systems.Lines such as the following specify swap devices in /etc/fstab:
/dev/sd1b none swap sw d48d0e3fc1c39531.k none swap sw
The initial swap device (root disk, partition b) need not appear in /etc/fstab, though it is not an error for it to do so.
Additional flags include:
server:/export/swap/client none swap sw,nfsmntpt=/swap
The swapctl
utility exits 0 on
success, and >0 if an error occurs.
The swapctl
program was originally
developed in NetBSD 1.3. It was ported to
OpenBSD 2.6 by Tobias Weingartner. The original
swapon
program, provided for backwards
compatibility, appeared in 4.0BSD.
The swapctl
program was written by
Matthew R. Green
<mrg@eterna.com.au>.
Local and remote swap files cannot be configured until the file systems they reside on are mounted read/write. The system startup scripts need to fsck(8) all local file systems before this can happen. This process requires substantial amounts of memory on some systems. If one configures no local block swap devices on a machine that has local file systems to check and rely only on swap files, the machine will have no swap space at all during system fsck(8) and may run out of real memory, causing fsck to abnormally exit and startup scripts to fail.
August 24, 2021 | OpenBSD-current |