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


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


       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.


       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

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


       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:

              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.

              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

              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

              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.


              user config

              the   swap  file,  target  of  the  whole  action  (defaults  to


       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:

       # /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
           /sbin/dphys-swapfile setup
           /sbin/dphys-swapfile swapon
           /sbin/dphys-swapfile swapoff
       exit 0

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

       In /etc/dphys-swapfile:



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