SWAPCTL(8)              OpenBSD System Manager's Manual             SWAPCTL(8)

NAME
     swapctl, swapon - system swap management tool

SYNOPSIS
     swapctl -A [-p priority] [-t blk|noblk]
     swapctl -a [-p priority] path
     swapctl -c -p priority path
     swapctl -d path
     swapctl -l | -s [-k]
     swapon -a | path
     swapoff path

DESCRIPTION
     The swapctl program adds, removes, lists and prioritizes swap devices and
     files for the system.  The swapon program acts the same as the swapctl
     program, as if called with the -a option, except if swapon itself is
     called with -a in which case, swapon acts as swapctl with the -A option.

     The options are as follows:

     -A      This option causes swapctl to read the /etc/fstab file for de-
             vices and files with an ``sw'' type, and adds all these entries
             as swap devices.  If no swap devices are configured, swapctl will
             exit with an error code.

     -a      The -a option requires that a path also be in the argument list.
             The path is added to the kernel's list of swap devices using the
             swapctl(2) system call.  When using the swapon form of this com-
             mand, the -a option is treated the same as the -A option, for
             backwards compatibility.

     -c      The -c option changes the priority of the listed swap device or
             file.

     -d path
             The -d option removes the listed path from the kernel's list of
             swap devices or files.

     -l      The -l option lists the current swap devices and files, and their
             usage statistics.

     -s      The -s option displays a single line summary of current swap
             statistics.

     -p priority
             The -p option sets the priority of swap devices or files to the
             priority argument.  This works with the -a, -c and -l options.

     -k      The -k option uses 1024 byte blocks instead of the default 512
             byte.

     -t blk|noblk
             This flag modifies the function of the -A option.  The -t option
             allows the type of device to add to be specified.  An argument of
             blk causes all block devices in /etc/fstab to be added.  An argu-
             ment of noblk causes all non-block devices in /etc/fstab to be
             added.  This option is useful in early system startup, where
             swapping may be needed before all file systems are available,
             such as during disk checks of large file systems.

SWAP OPTIONS
     When parsing the /etc/fstab file for swap devices, lines such as the fol-
     lowing specify additional swap devices:

           /dev/sd1b none swap sw 0 0

     Additional flags include:

     priority=N      This option sets the priority of the specified swap de-
                     vice to N.  The highest priority is 0, second priority is
                     1, etc.
     nfsmntpt=/path  This option is useful for swapping to NFS files.  It
                     specifies the local mount point to mount an NFS filesys-
                     tem.  Typically, once this mount has succeeded, the file
                     to be used for swapping on will be available under this
                     point mount.  For example:

                     server:/export/swap/client none swap sw,nfsmntpt=/swap

WARNINGS
     Local and remote swap files cannot be configured until the file systems
     they reside on are mounted read/write.  The system startup scripts need
     to fsck(8) all local file systems before this can happen.  This process
     requires substantial amounts of memory on some systems.  If you configure
     no local block swap devices on a machine that has local file systems to
     check and rely only on swap files, the machine will have no swap space at
     all during system fsck(8) and may run out of real memory, causing fsck to
     abnormally exit and startup scripts to fail.

SEE ALSO
     swapctl(2), fstab(5), mount_nfs(8), vnconfig(8)

HISTORY
     The swapctl program was originally developed in NetBSD 1.3.  It was port-
     ed to OpenBSD 2.6 by Tobias Weingartner.  The original swapon program,
     provided for backwards compatibility, appeared in 4.0BSD.

AUTHORS
     The swapctl program was written by Matthew R. Green <mrg@eterna.com.au>.

OpenBSD 3.0                      June 12, 1997                               2
