Comment by karlding
8 hours ago
Keep in mind that overlay file systems are designed to treat the lower layer as read only. Changes made in the merged view are written to the upper layer while the original lower files are untouched.
So if you need to persist changes into the lower layers, I think you may need to do tricks like taking snapshots and then swapping the bind mount (maybe with some diffing logic) or some other offline methods.
Ah that's good to know. That makes it more complicated than I was thinking because some mods obivously write data (other than cache etc which could be dropped between runs) that they expect to have persisted. Thanks for the heads up; I'll research this some more but I think it might stop there...