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 example, 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 determined by using the pagesize com-
mand. 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 multiple 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 starting 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 during 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 lines 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 speci-
fied, the area will be deleted starting at the second
page. When the command completes, swap blocks can no
longer be allocated 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 particu-
lar 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 map-
pings 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 reservation 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
Only the first 2 Gbyte of a block device larger than 2 Gbyte
in size can be used for swap in swapfs on a 32-bit operating
system. With a 64-bit operating system, a block device
larger than 2 Gbyte 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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