*/5 * * * * user /pathToCronJob/backUp.sh
The backUp.sh file contained:
########## This file does some synchronization very five minutes
rsync -alhprtXH --port=80 --rsh='ssh -p80' --delete --numeric-ids /sourceFolder/ /destinationFolder
80 was the port number I used for the port allowed in the firewall. --delete meant deleting the files in the destinationFolder if they are not found in the sourceFolder.
If not automated
The rsync script did not display anything. To display the progress, I used the command below without the task being automated:
rsync -avlhprtXH --port=80 --rsh='ssh -p80' --delete --progress --numeric-ids /sourceFolder/ /destinationFolder
I could see the progress made.
To be safe
I created the backups on a separate physical disk. If one disk failed, the other disk could help. The chance that two disks failed at the same time was small.