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/