System Administration Commands swap(1M)
NAME
swap - swap administrative interface
SYNOPSIS
/usr/sbin/swap -a swapname [swaplow] [swaplen]
/usr/sbin/swap -d swapname [swaplow]
/usr/sbin/swap -l
/usr/sbin/swap -s
DESCRIPTION
The swap utility provides a method of adding, deleting, and
monitoring the system swap areas used by the memory manager.
OPTIONS
The following options are supported:
-a swapname Add the specified swap area. This option can
only be used by the super-user. swapname is
the name of the swap file: for example,
/dev/dsk/c0t0d0s1 or a regular file. swaplow
is the offset in 512-byte blocks into the
file where the swap area should begin.
swaplen is the desired length of the swap
area in 512-byte blocks. The value of
swaplen can not be less than 16. For exam-
ple, if n blocks are specified, then (n-1)
blocks would be the actual swap length.
swaplen must be at least one page in length.
The size of a page of memory can be deter-
mined by using the pagesize command. See
pagesize(1). Since the first page of a swap
file is automatically skipped, and a swap
file needs to be at least one page in
length, the minimum size should be a multi-
ple of 2 pagesize bytes. The size of a page
of memory is machine dependent.
swaplow + swaplen must be less than or equal
to the size of the swap file. If swaplen is
not specified, an area will be added start-
ing at swaplow and extending to the end of
the designated file. If neither swaplow nor
swaplen are specified, the whole file will
be used except for the first page. Swap
areas are normally added automatically dur-
ing system startup by the /sbin/swapadd
script. This script adds all swap areas
which have been specified in the /etc/vfstab
file; for the syntax of these
specifications, see vfstab(4).
To use an NFS or local file-system swapname,
you should first create a file using
mkfile(1M). A local file-system swap file
can now be added to the running system by
just running the swap -a command. For NFS
mounted swap files, the server needs to
export the file. Do this by performing the
following steps:
1. Add the following line to
/etc/dfs/dfstab:
share -F nfs -o rw=clientname,root=clientname path-to-swap-file
2. Run shareall(1M).
3. Have the client add the following
line to /etc/vfstab:
server:path-to-swap-file - local-path-to-swap-filenfs \
--- local-path-to-swap-file -- swap ---
4. Have the client run mount:
# mount local-path-to-swap-file
5. The client can then run swap -a to
add the swap space:
# swap -a local-path-to-swap-file
-d swapname Delete the specified swap area. This option
can only be used by the super-user. swapname
is the name of the swap file: for example,
/dev/dsk/c0t0d0s1 or a regular file. swaplow
is the offset in 512-byte blocks into the
swap area to be deleted. If swaplow is not
specified, the area will be deleted starting
at the second page. When the command com-
pletes, swap blocks can no longer be allo-
cated from this area and all swap blocks
previously in use in this swap area have
been moved to other swap areas.
-l List the status of all the swap areas. The
output has five columns:
path The path name for the swap area.
dev The major/minor device number in
decimal if it is a block special
device; zeroes otherwise.
swaplo The swaplow value for the area in
512-byte blocks.
blocks The swaplen value for the area in
512-byte blocks.
free The number of 512-byte blocks in
this area that are not currently
allocated.
The list does not include swap space in the
form of physical memory because this space
is not associated with a particular swap
area.
If swap -l is run while swapname is in the
process of being deleted (by swap -d), the
string INDEL will appear in a sixth column
of the swap stats.
-s Print summary information about total swap
space usage and availability:
allocated The total amount of swap
space in bytes currently
allocated for use as backing
store.
reserved The total amount of swap
space in bytes not currently
allocated, but claimed by
memory mappings for possible
future use.
used The total amount of swap
space in bytes that is
either allocated or
reserved.
available The total swap space in
bytes that is currently
available for future reser-
vation and allocation.
These numbers include swap space from all
configured swap areas as listed by the -l
option, as well swap space in the form of
physical memory.
USAGE
On the 32-bit operating system, only the first 2 Gbytes -1
are used for swap devices greater than or equal to 2 Gbytes
in size. On the 64-bit operating system, a block device
larger than 2 Gbytes can be fully utilized for swap up to 2
**63 -1 bytes.
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment
variables that affect the execution of swap: LC_CTYPE and
LC_MESSAGE.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________|_____________________________|
| Availability | SUNWcsu |
|_____________________________|_____________________________|
SEE ALSO
pagesize(1), mkfile(1M), shareall(1M), getpagesize(3C),
vfstab(4), attributes(5), largefile(5)
WARNINGS
No check is done to determine if a swap area being added
overlaps with an existing file system.
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