#!/bin/sh
#mount all filesystems in /etc/fstab not marked "noauto"
#create /var and /tmp directories and ensure that they are on
#writable filesystems.

prunePath() {
#prune non-existant components from the specified filesystem path
  path=$1
  until [ -e "$path" ]; do
    newPath=`dirname $path` || return 2
    [ "$newPath" = "$path" ] && return 1
    path=$newPath
  done
  echo $path
}

redoIfRO() {
#try command $2 writing to directory $1
#retry cmd after remounting fs rw if command $2 reports read-only filesystem
  dir=$1; shift
  err=`eval "$@" 2>&1` || {  #test for cmd trying to write to r/o fs 
    echo $err | grep -q Read-only && target=`prunePath $dir` && {
      df $target | {
        read header && read dev blks used avail use mntpt extra &&
          echo "Making $mntpt writable because it will contain $dir" >&2 &&
          mount -oremount,rw,noatime $dev $mntpt
      } && eval "$@"
    }
  }
}

realPath() {
#like busybox realpath,
# but return name of non-existent path at end of a symlink chain
#beware: this may change $PWD
  firstPath=$1
  path=$1
  maxLinks=100
  while newPath=`readlink $path 2>/dev/null`; do 
    let maxLinks=$maxLinks-1
    [ $maxLinks -lt 0 ] && {
      echo "sysmount: Too many levels of symbolic links for $firstPath" >&2
      return 1
    }
    [ $newPath = ${newPath#/} ] && {
      cd `dirname $path`      
      newPath=$PWD/$newPath
    }
    path=$newPath
  done
  echo $path
}


case "$1" in
    start)
      echo "Mounting filesystems and swapfiles defined in /etc/fstab"      
      mount -a
      swapon -a 2>/dev/null

      #Set up temporary directories, preserves existing symlinks
      tmp=`realPath /tmp` &&
        redoIfRO "$tmp" "rm -rf $tmp && mkdir -p $tmp && chmod 1777 $tmp"
      var=`realPath /var` && {
        cd $var 2>/dev/null || {
          redoIfRO "$var" "mkdir -p $var && touch $var" && cd $var
        } && {
          log=`realPath $var/log` &&
            redoIfRO $log "mkdir -p $log && chgrp log $log && chmod g+w $log"
          etc=`realPath $var/etc/ppp` &&
            redoIfRO $etc "mkdir -p $etc && touch $etc"
          run=`realPath $var/run` &&
            redoIfRO $run \
             "rm -rf $run/* $run/.[^.]* && mkdir -p $run && touch $run"
          lock=`realPath $var/lock` &&
            redoIfRO $lock \
             "rm -rf $lock/* $lock/.[^.]* && mkdir -p $lock && chgrp tty $lock"
        }
      }
       ;;
                         
    stop)
      echo -n "Unmounting file systems ... "
      swapoff -a 2>/dev/null
      umount -ar 2>&1 | grep -v "none busy"
      echo "Done!"
       ;;
       
    *)
       echo "usage: start|stop"
       echo "on start:  mount all filesystems in fstab not marked \"noauto\""
       echo "on stop:  umount all filesystems (except proc and root)"
       ;;
esac