NAME

       dphys-swapfile - set up, mount/unmount, and delete an swap file

SYNOPSIS

       dphys-swapfile setup|install|swapon|swapoff|uninstall

DESCRIPTION

       dphys-swapfile  computes  the  size for an optimal swap file (and resizes an existing swap
       file if necessary), mounts an swap file, unmounts it, and deletes it it is not wanted  any
       more.

OPTIONS

       There is only one parameter, an command, which can be either of these:

       setup  and  install  Both  tell  dphys-swapfile  to compute the optimal swap file size and
              (re-)generate an fitting swap file. Default it 2 times RAM size. This can be called
              at  boot  time, so the file allways stays the right size for current RAM, or run by
              hand whenever RAM size has changed.

       swapon and swapoff These run the swapon and swapoff commands on the  swapfile.  Note  that
              direct  swapon/off from /etc/fstab is not possible, as that is (at least on Debian)
              done in the same script that mounts /var (which is where the swap file most  likely
              resides).  And  we  need  to  do  our setup between those actions. So we pass up on
              /etc/fstab, and do our own swapon/off here.

       uninstall
              Gets rid of an unwanted swap file, reclaiming its disk space.

CONFIG

       The config file /etc/dphys-swapfile allows the user to set up the working environment  for
       dphys-swapfile.

       This  config  file is a sh script fragment full of assignments, which is sourced. Standard
       sh syntax rules apply. Assignments are:

       CONF_SWAPFILE
              Set where the swap file should be placed. Defaults to  /var/swap.  It  is  unlikely
              that  you  will need to change this, unless you have very strange partitioning, and
              then you will most likely be using an swap partition anyway.

       CONF_SWAPSIZE
              Set size to this absolute value, in  MBytes.  Leaving  this  empty  (which  is  the
              Default)  uses  an  computed  value  as  size  instead. This is unlikely to ever be
              needed, unless in some strange diskspace situations. Note, that  swap  enabled  and
              size   smaller   than   RAM   may   causes  kernal-internal  VM  troubles  on  some
              kernels/systems.

       CONF_SWAPFACTOR
              Set size to computed value. Uses this value  times  RAM  size.  It  so  dynamically
              adapts  to RAM size, guarantees enough swap on large RAM, without going into excess
              diskspace on small RAM (and disk?) systems. Defaults to 2, which gives swap size  =
              2 * RAM size.

       CONF_MAXDISK_PCT
              Sets  the  maximal percentage of the remaining disk space which may be used for the
              swap file. Takes potentially existing dphys-swapfile swap files into account,  i.e.
              adds  their  size  to  the  available disk space before calculating the percentage.
              Defaults to 50. Set it to the empty string to disable this check.

       CONF_MAXSWAP
              Set size restriction  of  maximal  computed  and  absolute(!)  values,  in  MBytes.
              Defaults to 2048 which was a former 32bit kernel limit for the swapfile size and is
              now a limit to prevent unusually and senselessly big swap files on systems  with  a
              lot of RAM.

FILES

       /etc/dphys-swapfile
              user config

       $CONF_SWAPFILE
              the swap file, target of the whole action (defaults to /var/swap)

EXAMPLES

       dphys-swapfile  is  usually  run  at  system  startup and shutdown from an /etc/init.d (or
       /etc/rc.d) script, such as this (minimal) one:

       #!/bin/sh
       # /etc/init.d/dphys-swapfile - automatically set up an swapfile
       # author franklin, last modification 2004.06.04
       # This script is copyright ETH Zuerich Physics Departement,
       #   use under either modified/non-advertising BSD or GPL license
       case "$1" in
         start)
           /sbin/dphys-swapfile setup
           /sbin/dphys-swapfile swapon
           ;;
         stop)
           /sbin/dphys-swapfile swapoff
           ;;
       esac
       exit 0

       If an sysadmin wants to have the swapfile in another place, say /var/tmp/swap, he can use:

       In /etc/dphys-swapfile:

       CONF_SWAPFILE=/var/tmp/swap

AUTHOR

       neil@franklin.ch, http://neil.franklin.ch/