Update README.md

Added a hint regarding utils.sh

README.md

@@ -2,3 +2,11 @@ nagios-nrpe-check_glusterfs
 ===========================
 
 Fork of Mark Ruys' check_glusterfs from http://exchange.nagios.org/directory/Plugins/System-Metrics/File-System/GlusterFS-checks/details
+
+Hint: If you receive the error message that utils.sh is missing, you should check if the script is existing on your system and in the same folder as the check.
+
+On Debian 7, the command
+ln -s /usr/lib/nagios/plugins/utils.sh utils.sh
+will help. 
+
+An alternative would be to edit the check and adapt the line ". $PROGPATH/utils.sh" according to your needs.