note to myself and anyone with same problem who finds the thread:

stumbled on psync: A naive tool for syncing partitions using rsync which sounds like it’s at lest trying to do this task.

No documentation, no users, no project changes in 6 years… Will give it a try another time.

hmmm I think this is a bit beyond me; at this point I don’t want to create an additional side project. I might learn about the more modern spiffy file systems in a few years.

Thanks I will look at rdiff. I am not sure if rsync is able to “see inside” the *.img files to discern the individual files. If it can then it would be helpful because I could just re-write the same file over and over again and keep backups using rsync or any of the various rsync-derrived tools?

The filesystem will be cold at time of back up because I will need to shut it down, remove the card from the console and put it into my computer’s reader so no worries about that.