#!/bin/sh
# validate /etc/fstab against the current UUID list in
# /etc/uuid_by_partition
#
. /etc/default/functions
pfile=/etc/uuid_by_partition

#
# use debug to find out what is going on
test "$1" = start -o "$1" = debug || exit 0

#
# obtain the current list of parititions with UUIDs
newlist="$(uuid_by_partition)"

if test -r "$pfile"
then
	# read the old list
	oldlist="$(cat "$pfile")"
	#
	# if it hasn't changed nothing need be done
	test "$newlist" = "$oldlist" && exit 0
	#
	# it has changed, but this only matters if
	# a previously existing uuid has moved, build
	# a list of old device vs new device for every
	# uuid which has moved
	changedlist="$(
		{	echo "$oldlist"
			echo "$newlist"
		} | awk 'device[$2] == ""{device[$2] = $1}
			device[$2] != $1{print device[$2], $1}')"

	if test -n "$changedlist"
	then
		# at least one partition has moved, scan the
		# current fstab to see if it has a reference
		# to this partition
		changedfstab="$(
			{	echo "$changedlist"
				echo '#fstab'
				cat /etc/fstab
			} | awk 'BEGIN{list=1}
				list==1 && $0=="#fstab"{list=0; continue}
				list==1{new[$1] = $2; continue}
				new[$1] != ""{print $1, new[$1]}')"

		# if this list is not empty edit the fstab
		if test -n "$changedfstab"
		then
			rm -f /tmp/fstab.$$
			# if the edit fails then do not overwrite the old
			# partition list - just exit with an error
			{	echo "$changedlist"
				echo '#fstab'
				cat /etc/fstab
			} | awk 'BEGIN{list=1}
				list==1 && $0=="#fstab"{list=0; continue}
				list==1{new[$1] = $2; continue}
				new[$1] != ""{$1 = new[$1]}
				{print}' >/tmp/fstab.$$ || {
				if test "$1" = start
				then
					logger -s "/etc/init.d/fixfstab: /tmp/fstab.$$: awk failed"
				else
					echo "debug: awk script failed with:" >&2
					echo "$changedlist" >&2
					echo "output in /tmp/fstab.$$" >&2
				fi
				exit 1
			}

			if test "$1" = start
			then
				mv /tmp/fstab.$$ /etc/fstab || {
					logger -s "/etc/init.d/fixfstab: /tmp/fstab.$$: update failed"
					exit 1
				}
			else
				echo "debug: fstab changed:"
				diff -u /etc/fstab /tmp/fstab.$$
			fi
		fi
	fi
fi

# write the new list to the file, only if we
# are doing something...
test "$1" = start && echo "$newlist" >"$pfile"

exit 0