I'm currently tasked with bringing up a existing server to (at least more) professional standards - with as little disruption as possible to end-users. To have a proper rollback, I need to backup the existing server's root fs, which is currently ext4 inside a primary disk partition - not LVM, which would make the whole show a mere finger excercise. I'd like to avoid shutting down the server.
Is it even possible under these circumstances?