I have a virtual server that is constantly running, lately we tried to do a backup for it and we were surprised that the modification date of all the image files is a couple weeks old. We are trying to take a backup of the server VM image every 6 hours while keeping the server running but since the files are not being modified we are not sure how to force VM to update the server files so we can back them up.
EDIT: Just wanted to add that the VM in question is an Ubuntu Server VMWare Workstation image.
EDIT2: A screenshot of the directory that contains the VM files is shown below. Note that we restarted the host machine on September 9th and since then the files did not change although the VM has been up and running for two days now.