--- etc/init.d/halt	2013-07-08 14:03:24.216175133 +0200
+++ etc/init.d/ltsp-halt	2013-07-08 14:04:14.208174948 +0200
@@ -84,6 +84,12 @@
     OMITARGS="$OMITARGS -o $(cat $i)"
 done
 
+# Skip unionfs
+UNION=`pgrep unionfs 2> /dev/null`
+if [ $? -eq 0 ]; then
+    OMITARGS="${OMITARGS} -o ${UNION}"
+fi
+
 #kill_all $"Sending all processes the TERM signal..." -15 $OMITARGS
 # No need to sleep and kill -9 if no processes to kill were found
 if [ "$?" == 0 ]; then