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 a very conservative
check does not conclude that there is sufficient VM (memory +
remaining swap devices) to run the system.
The
-f
option turns off this check, which could deadlock the system
if there is insufficient swap space remaining.
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.
|
|
