#! /bin/sh
# /sbin/dphys-swapfile - automatically set up an swapfile
# author franklin, last modification 2004.06.11
# This script is copyright ETH Zuerich Physics Departement,
#   use under either BSD or GPL license

# get ready to work
PATH=/sbin:/bin:/usr/sbin:/usr/bin
export PATH

# what we are
NAME=dphys-swapfile

# this is what we want, 2 times RAM size
SWAPFACTOR=2
# this is a (outdated?) kernel limit (in MBytes), do not overrun it
MAXSWAP=2048

# where we want the swapfile to be, this is the default
CONF_SWAPFILE=/var/swap

# check user config file(s), let user overwride settings, swap file filename
CONFFILE=/etc/${NAME}
DCONFFILE=/etc/default/${NAME}
if [ -f ${CONFFILE} ] ; then
  . ${CONFFILE}
fi
if [ -f ${DCONFFILE} ] ; then
  . ${DCONFFILE}
fi


case "$1" in

  setup)
    # (re-)size/-generate

    # compute automatic optimal size
    /bin/echo -n "computing size"
    # this seems to be the nearest to physical RAM size, lacks about 60k
    KCORESIZE=`/bin/ls -l /proc/kcore | /usr/bin/awk '{ print $5 }'`
    # make MBytes which rounded down will be exactly 1 too few, so add 1
    MEMSIZE=`/usr/bin/expr ${KCORESIZE} / 1048576 + 1`
    # default, without config file overwriding, swap=2*RAM
    CONF_SWAPSIZE=`/usr/bin/expr ${MEMSIZE} '*' ${SWAPFACTOR}`

    # re-check user config file(s), so late so can overwrite computed size
    if [ -f ${CONFFILE} ] ; then
      . ${CONFFILE}
    fi
    if [ -f ${DCONFFILE} ] ; then
      . ${DCONFFILE}
    fi

    # announce end resulting config
    /bin/echo -n ": want ${CONF_SWAPFILE}=${CONF_SWAPSIZE}MByte"

    # check for legitimate swap size and restrict to it
    if [ ${CONF_SWAPSIZE} -gt ${MAXSWAP} ] ; then
      /bin/echo -n ", limiting to kernel limit: ${MAXSWAP}MBytes"
      CONF_SWAPSIZE=${MAXSWAP}
    fi


    # we will be later starting, and in between possible deleting/rebuilding
    #   so switch off any allready running swapfile, to avoid errors
    #   test here for running, as else also error from swapoff
    if [ x`/sbin/swapon -s | /bin/grep ${CONF_SWAPFILE} | \
         /usr/bin/cut -f 1 -d " "` != x ] ; then
      /sbin/swapoff ${CONF_SWAPFILE} 2>&1 > /dev/null
    fi


    # compare existing swapfile (if one exists) to see if it needs replacing
    if [ -f ${CONF_SWAPFILE} ] ; then

      /bin/echo -n ", checking existing"

      # we need bytes for comparing with existing swap file
      SWAPBYTES=`/usr/bin/expr ${CONF_SWAPSIZE} '*' 1048576`

      FILEBYTES=`/bin/ls -l ${CONF_SWAPFILE} | /usr/bin/awk '{ print $5 }'`

      # wrong size, get rid of existing swapfile, after remake
      if [ x${FILEBYTES} != x${SWAPBYTES} ] ; then

        # updates to this section need duplicating in postrm script
        #   can not simply make subroutine here and call that from postrm
        #     as this script is deleted before  postrm purge  is called

        /bin/echo -n ": deleting wrong size file (${FILEBYTES})"

        # deactivate before deleting
        $0 swapoff

        # and the file is also gone ...
        /bin/rm ${CONF_SWAPFILE}

        # remove any entry for mounting existing swapfile from /etc/fstab
        #   do this first, so no deadlock if reboot and attempted swapon
        /bin/grep -v "^${CONF_SWAPFILE}" /etc/fstab > /etc/.fstab
        /bin/mv /etc/.fstab /etc/fstab

      else

        /bin/echo -n ": keeping it"

      fi
    fi

    # if no swapfile (or possibly old one got deleted) make one
    if [ ! -f ${CONF_SWAPFILE} ] ; then

      /bin/echo -n ", generating swapfile ..."

      # first deleting existing mount lines, if any there (same code as above)
      /bin/grep -v "^${CONF_SWAPFILE}" /etc/fstab > /etc/.fstab
      /bin/mv /etc/.fstab /etc/fstab

      /bin/dd if=/dev/zero of=${CONF_SWAPFILE} bs=1048576 \
        count=${CONF_SWAPSIZE} 2> /dev/null
      /sbin/mkswap ${CONF_SWAPFILE} > /dev/null

      # ensure that only root can read possibly critical stuff going in here
      /bin/chmod 600 ${CONF_SWAPFILE}

      # do not mount swapfile via fstab, because S35mountall.sh is already done
      #   so just add warning comment line that swapfile is not in fstab
      #     and so gets mounted by this script
      # get rid of possibly existing comment about swapfile mounted by script
      /bin/grep -v "^# a swapfile" /etc/fstab > /etc/.fstab
      /bin/grep -v ${NAME} /etc/.fstab > /etc/fstab
      # add new comment about this
      /bin/echo -e "# a swapfile is not a swappartition, no swapon|off" \
        "from here, use  ${NAME} swap[on|off]  for that" >> /etc/fstab

      # and inform user what we did
      /bin/echo -n " of ${CONF_SWAPSIZE}MBytes"

    fi

    /bin/echo

    ;;


  swapon)
    # as there can be no swapon in /etc/fstab, do it from here
    #   this is due to no possible insertion of code (at least in Debian)
    #     between mounting of /var (where swap file most likely resides)
    #     and executing swapon, where the file already needs to be existing

    if [ -f ${CONF_SWAPFILE} ] ; then
      /sbin/swapon ${CONF_SWAPFILE} 2>&1 > /dev/null
    else
      /bin/echo "$0: ERROR: swap file ${CONF_SWAPFILE} missing!"
    fi

    ;;


  swapoff)
    # as there can also be no swapoff in /etc/fstab, do it from here

    if [ x`/sbin/swapon -s | /bin/grep ${CONF_SWAPFILE} | \
         /usr/bin/cut -f 1 -d " "` != x ] ; then
      /sbin/swapoff ${CONF_SWAPFILE} 2>&1 > /dev/null
    fi

    ;;


  uninstall)
    # note: there is no install), as setup) can run from any blank system
    #   it auto-installs as side effect of recomputing and checking size

    # deactivate before deleting
    $0 swapoff

    if [ -f ${CONF_SWAPFILE} ] ; then
      # reclaim the file space
      /bin/rm ${CONF_SWAPFILE}
    fi

    # and get rid of comment about swapfile mounting
    /bin/grep -v "^# a swapfile" /etc/fstab > /etc/.fstab
    /bin/grep -v ${NAME} /etc/.fstab > /etc/fstab

    ;;


 *)
    /bin/echo "Usage: $0 {setup|swapon|swapoff|uninstall}"

    exit 1
    ;;

esac

exit 0