The
swapon
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
-E
option causes each of following devices to receive a
BIO_DELETE
command.
This command marks the device's blocks as unused, except those that
might store a disk label.
This marking can erase a crash dump.
To delay
swapon
for a device until after
savecore
has copied the crash dump to another location, use the
"late"
option.
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:
|
| -F fstab
|
| |
Specify the
fstab
file to use (in conjunction with
-a -).
|
|
The
swapctl
utility exists primarily for those familiar with other
BSD Ns s
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
BLOCKSIZE
environment variable is used if not specifically
overridden.
512 byte blocks are used by default.
|
|
