i just notices that there is 'overlay file system' option in 'raspi-config'. It must be some sort of new feature as did not notice that before.
My question is. If overlay in enabled, what folders are write protected?
Is it entire SD card or just part of it?
What about USB drive connected?
This feature would make my life much easier for testing purposes but i would like to be sure that if for example i will install tons of software while overlay is enabled, then after reboot my Raspbian will exaclty in the same state like it was before i turned overlay on.
Thanks for any clues in that matter.