Update 'README.md'

README.md

@@ -55,10 +55,24 @@ FROMSSHPORT=22                    # The ssh port of the system from which the
 ```
 
 ### Crontab example
-Create a backup every two hours:
+Create a backup every two hours (use flock to prevent duplicate scripts from running):
 
 ```bash
-0 */2 * * * ~/backup.sh
+0 */2 * * * flock -n ~/backup.lock ~/backup.sh
+```
+
+### Exclude file example
+This example can be used for a full system backup (use only "/" as source for a full system backup). Copied from the [Arch Wiki](https://wiki.archlinux.org/index.php/rsync#Full_system_backup).
+
+```
+/dev/*
+/proc/*
+/sys/*
+/tmp/*
+/run/*
+/mnt/*
+/media/*
+/lost+found
 ```
 
 ## Inspiration