dpkg-squashfs.sh

#! /bin/sh
### BEGIN INIT INFO
# Provides:          dpkg-squashfs
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: Squashfsed /var/lib/dpkg
# Description:       Use squashfs to speedup dpkg cold start.
#                    Required kernel modules: aufs, squashfs
#                    Required packages: squashfs-tools
### END INIT INFO

PATH=/sbin:/usr/sbin:/bin:/usr/bin
DESC="Squashfsed dpkg directory"
SCRIPTNAME=/etc/init.d/$NAME
. /lib/lsb/init-functions

DPKG_DIR=/var/lib/dpkg
DPKG_RO=/var/lib/.dpkg.ro
DPKG_RW=/var/lib/.dpkg.rw
SQUASHFS_FILE=/var/lib/dpkg.squashfs

mount_squashfs()
{
	mkdir -p ${DPKG_RO}
	mount -r -t squashfs -o loop ${SQUASHFS_FILE} ${DPKG_RO}
}

squashfs_mounted()
{
	mount | grep -q ${DPKG_RO}
}

umount_squashfs()
{
	umount ${DPKG_RO}
}

mount_aufs()
{
	mkdir -p ${DPKG_RW}
	mount -t aufs -o noplink,br:${DPKG_RW}=rw:${DPKG_RO}=rr dpkgfs ${DPKG_DIR} > /dev/null 2>&1
}

aufs_mounted()
{
	mount | grep -q ^dpkgfs
}

umount_aufs()
{
	umount ${DPKG_DIR}
}

make_squashfs()
{
	rm -f ${SQUASHFS_FILE}.new
	mksquashfs ${DPKG_DIR} ${SQUASHFS_FILE}.new -no-progress > /dev/null 2>&1
}

silent_move()
{
	if [ -e $1 ]; then
		rm -rf $2
		mv $1 $2
	fi
}

do_start()
{
	if ! [ -e ${SQUASHFS_FILE} ]; then
		make_squashfs
		silent_move ${SQUASHFS_FILE}.new ${SQUASHFS_FILE}
	fi
	mount_squashfs && mount_aufs
}

do_stop()
{
	if aufs_mounted; then
		make_squashfs
		fuser -k -m ${DPKG_DIR}
		umount_aufs
	fi
	squashfs_mounted && umount_squashfs
	
	silent_move ${SQUASHFS_FILE}.new ${SQUASHFS_FILE}
	silent_move ${DPKG_RW} ${DPKG_RW}.old
	
	rm -rf ${DPKG_RW}.old
	rm -rf ${DPKG_RO}
	return 0
}

case "$1" in
  start)
	[ "$VERBOSE" != no ] && log_daemon_msg "Starting $DESC" "$NAME"
	do_start
	case "$?" in
		0) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
		*) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
	esac
	;;
  stop)
	[ "$VERBOSE" != no ] && log_daemon_msg "Stopping $DESC" "$NAME"
	do_stop
	case "$?" in
		0) [ "$VERBOSE" != no ] && log_end_msg 0 ;;
		*) [ "$VERBOSE" != no ] && log_end_msg 1 ;;
	esac
	;;
  status)
	mount | grep ${DPKG_DIR}
	;;
  restart|force-reload)
	log_daemon_msg "Restarting $DESC" "$NAME"
	do_stop
	case "$?" in
	  0|1)
		do_start
		case "$?" in
			0) log_end_msg 0 ;;
			1) log_end_msg 1 ;; # Old process is still running
			*) log_end_msg 1 ;; # Failed to start
		esac
		;;
	  *)
	  	# Failed to stop
		log_end_msg 1
		;;
	esac
	;;
  *)
	echo "Usage: $SCRIPTNAME {start|stop|status|restart|force-reload}" >&2
	exit 3
	;;
esac

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