swapon - Specifies additional disk partitions for paging
and swapping
/sbin/swapon [-a | -v | -p | -s | -d | -F] [-D
device] [-l size] [-h size] filename
Installs all paging partitions specified in the
/etc/sysconfigtab file. Generates verbose output. Specifies
the filename given in the command is the preferred
paging device. Displays swap space utilization. For each
swap partition, this option displays the total amount of
allocated swap space, the amount of swap space that is
being used, and the amount of free swap space. Sets the
first specified swap device as the system dump device,
providing the system dump device was not previously set.
Force the use of the specified swap device, even if either
of the following conditions are true: You specified a partition
that is currently in use (that is, the partition
contains a valid file system). The device contains other
file partitions that are currently in use.
If you do not specify the -F option and the partition
is in use, the swapon command displays a partition
check warning message. It then gives you an
opportunity to override the partition check.
Explicitly sets the system dump device to be the
specified device, even if the system dump device
was previously set. Specifies the low water mark.
Specifies the high water mark.
Specifies the device special file name.
The swapon command is used to specify additional disk partitions
for paging and swapping. A paging partition is a
block special device. (Tru64 UNIX does not currently support
paging and swapping to a regular file. All paging
and swapping areas must be block special devices.) The
swapon command uses a priority default of 4 for block special
devices. Calls to swapon normally occur in the system
multiuser state initialization.
When you make more swap space available with the swapon
command, the additional swap space is available until the
system is rebooted. To make additional swap space permanent,
you must specify the swap device entry in the
/etc/sysconfigtab file.
The swapon command options can override the partition
specifications in the /etc/sysconfigtab file. You must be
superuser or have the mount command authorization to run
the swapon command. System administrators and operators
(users with the sysadmin and operator command authorizations,
respectively) usually are given mount command
authorization. See dop(8) for information about giving
certain users authorization to issue privileged commands
without knowing the root password.
You can use Logical Storage Manager (LSM) volumes for
additional swap space. For high system availability, you
can mirror the LSM volumes. The Logical Storage Manager
manual describes how to use the swapon command to configure
an LSM mirrored volume as additional swap space.
There are two strategies for swap space allocation: immediate
mode and deferred or over-commitment mode. The two
strategies differ in the point in time at which swap space
is allocated. If immediate mode is used, swap space is
allocated when modifiable virtual address space is created.
If deferred mode is used, swap space is not allocated
until the system needs to write a modified virtual
page to swap space. Immediate mode is the default swap
space allocation strategy.
Immediate mode is more conservative than deferred mode
because each modifiable virtual page is assigned a page of
swap space when it is created. If you use the immediate
mode of swap space allocation, you must allocate a swap
space that is at least as large as the total amount of
modifiable virtual address space that will be created on
your system. Immediate mode requires significantly more
swap space than deferred mode because it guarantees that
there will be enough swap space if every modifiable virtual
page is modified.
If you use the deferred mode of swap space allocation, you
must estimate the total amount of virtual address space
that will be both created and modified, and compare that
total amount with the size of your system's physical memory.
If this total amount is greater than the size of
physical memory, the swap space must be large enough to
hold the modified virtual pages that do not fit into your
physical memory. If your system's workload is complex and
you are unable to estimate the appropriate amount of swap
space by using this mode, you should first use the default
amount of swap space and adjust the swap space as needed.
To determine which swap space allocation mode is being
used, check the setting of the vm-swap-eager attribute in
/etc/sysconfigtab. If this value is either not specified
or set to 1, the system uses immediate swap mode. If it
is set to 0 (zero), the system uses deferred mode.
There is no way to stop paging and swapping on a partition.
It is therefore not possible to use swap devices
that can be dismounted during system operation.
Swap space is also used during a system crash dump. In
planning your swap space allocation you should also consider
your crash dump requirements. See the System Administration
manual for information on crash dumps.
special-device or an overlapping partition is open. Quitting...
Explanation:
This message indicates that you tried to add a partition
as a swap device that is actively in use by
UFS, AdvFS, swap, or LSM.
User Action:
Specify a different swap device. special-device is
marked in use for fstype in the disklabel. If you
continue with the operation you can possibly
destroy existing data. CONTINUE? [y/n]
Explanation:
This message indicates that you tried to use a partition
as a swap device that is not currently in
active use but is marked for use in the disk
label's partition map. For example, the partition
may be part of an LSM volume or an AdvFS domain.
User Action:
Specify a different swap device or override the
warning.
If you know that the partition you specified to
swapon does not contain any data, you can choose to
override the warning. In this case, the fstype in
the disk label will be modified to swap.
Note that you can use the disklabel -s command to
set the fstype in the disk label to unused for partitions
that do not contain any valid data. See
disklabel(8) for more information. Partition(s)
which overlap special-device are marked in use If
you continue with the operation you can possibly
destroy existing data. CONTINUE? [y/n]
Explanation:
This message indicates that the partition you specified
is not marked for use, but other, overlapping
partitions on the disk are marked for use.
User Action:
Specify a different swap device or override the
warning.
If you override this warning, the fstype in the
disk's label will be modified. The partition you
specified to swapon will be marked as in use as a
swap device and all overlapping partitions will be
marked UNUSED.
Entering the swapon comand with no parameters displays the
following help message: # swapon usage: swapon [-avpsdF]
[-D device] [-l size] [-h size] filename The following
example shows a swap device entry in an /etc/sysconfigtab
file:
vm:
swapdevice=/dev/disk/dsk0b,/dev/disk/dsk1b The
following example adds the /dev/disk/dsk0b block
device file as swap space: # swapon /dev/disk/dsk0b
The following example tries to add a partition that
is marked for use as a swap device: #
/usr/sbin/swapon /dev/disk/dsk11g
/dev/disk/dsk11g disk is marked in use for LSMpubl
in the disklabel. If you continue with the operation
you can possibly destroy existing data. CONTINUE?
[y/n]
Partition g of disk dsk11 is part of a disk marked
for use by LSM. If LSM is not actively using this
partition and the partition does not contain any
data, you may want to override this warning, by
answering y. In this case, partition g will be
marked as swap in the disk label. The following
example tries to add a partition as a swap device
whose overlapping partitions are marked for use: #
/usr/sbin/swapon /dev/disk/dsk11c
Partition(s) which overlap /dev/disk/dsk11c are
marked in use. If you continue with the operation
you can possibly destroy existing data. CONTINUE?
[y/n]
If you answer yes, partition c on disk dsk11 will
be marked swap in the disk label and all partitions
that overlap c will be marked UNUSED. The following
example tries to add a partition that is currently
in use as a swap device: # /usr/sbin/swapon
/dev/disk/dsk11g
/dev/disk/dsk11g or an overlapping partition is
open. Quitting... The following example tries to
add a partition that does not have a disk label as
a swap device: # /usr/sbin/swapon /dev/disk/dsk11c
The disklabel for /dev/disk/dsk11c does not exist
or is corrupted. Quitting...
See disklabel(8) for information on installing a
disk label on a disk.
Specifies the command path. Specifies information about
file systems and swap devices.
Commands: dop(8), savecore(8)
Functions: swapon(2)
Others: sys_attrs(5), sys_attrs_vm(5)
System Administration
Logical Storage Manager
Security
swapon(8)
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