I have an elderly relative who always seems to manage to accidentally mess up the computer. (it's really hard to make a computer accident(=idiot)-proof.)
what I need is that I can set up a computer (e.g., skype, browser, email, with credentials already input) and when the computer is rebooted, it is exactly back to how it was, no matter almost whatever this person has done. I trust that this person won't figure out how to mount an unmounted volume. I presume that I will need to update the software (browser, security patches, skype, etc.) once a year or so.
I see a few possible approaches:
on bootup, everything important on root '/' is copied to a RAM disk, control is passed to it, and the real '/' is unmounted.
on bootup, an rsync from a stored image copy on another partition forces the root partition back to the same state.
on bootup, the root partition turns into ro and all file activity goes to an overlay file system.
snapshots as in a VM are probably not a great idea, because VMs are slow and themselves corruptible, possibly exposable to the user, too. making the user folder RO could result in error message, which would be endlessly confusing to my user, so this is not possible.
recommendations for macos appreciated.