swap(1M)						  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 [-h | -k]

       /usr/sbin/swap -s [-h]

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 [swaplow] [swaplen]

	   Add	the  specified	swap area. This option can only be used by the superuser or by one who has assumed the Primary Administrator role.
	   swapname is the name of the swap area or regular file. For example, on system running a UFS root file system, specify a slice, such	as
	   /dev/dsk/c0t0d0s1,  or  a  regular  file  for  a  swap  area.  On  a  system  running  a ZFS file system, specify a ZFS volume, such as
	   /dev/zvol/dsk/rpool/swap, for a swap area. Using a regular file for swap is not supported on a ZFS file system. In addition, you cannot
	   use the same ZFS volume for both the swap area and a dump device when the system is running a ZFS root file system.

	   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 page-
	   size 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 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 line to /etc/vfstab:

			server:path-to-swap-file -  local-path-to-swap-file nfs 
			     --- 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 spec-
	   ified, 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.

       -h

	   All sizes are scaled to a human readable format. Scaling is done by repetitively dividing by 1024.

       -k

	   Write the files sizes in units of 1024 bytes.

       -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 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

       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 attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO

       pagesize(1), mkfile(1M), shareall(1M), getpagesize(3C), vfstab(4), attributes(5), largefile(5)

NOTES

       For information about setting up a swap area with ZFS, see the ZFS Administration Guide.

WARNINGS

       No check is done to determine if a swap area being added overlaps with an existing file system.

SunOS 5.11							    11 Apr 2008 							  swap(1M)