Manual Pages for UNIX Operating System command usage for man swap

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 Pri-
         mary Administrator role. swapname is  the  name  of  the
         swap  area  or regular file. For example, on system run-
         ning 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  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  multiple  of  2  pagesize
         bytes.  The  size  of  a  page  of  memory  is  machine-
         dependent.




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System Administration Commands                           swap(1M)



         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 sys-
         tem 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.



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System Administration Commands                           swap(1M)



         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 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



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System Administration Commands                           swap(1M)



         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



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System Administration Commands                           swap(1M)



     LC_MESSAGE.

ATTRIBUTES
     See attributes(5) for descriptions of the  following  attri-
     butes:



     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Availability                | SUNWcs                      |
    |_____________________________|_____________________________|


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.





























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