Here's an useful collection of links I have used to properly set a generic RPi OS in read/only mode in order to:
- Avoid OS data corruption on improper power loss events
- Avoid SD corruption, SD storage devices are not made for long term operations with heavy read/write events done from an OS
- Have long lasting machines dedicated to single services, when nothing changes your system is stable and keeps your services running without surprises
- Making
roa root partition is easy but it doesn't solve your problems if you don't design your system to adapt to it
- https://hallard.me/raspberry-pi-read-only/
Quite decent reference, it covers most cases and it's a good starting point for a quite common and standard system, when you customize a lot of things you're on your own - https://gist.github.com/yeokm1/8b0ffc03e622ce011010
Focused on Linux Arch but suggested hints are valid for everyone, just keeppacmanhints away if you're not using Arch - https://mtyka.github.io/hardware/2018/10/09/read-only-pi.html
Preventing SD corruption, mount everything in read-only and keep few things ontmpfs(/var/log, /var/tmp, /var/lib/, ...) quite reasonable to me - http://wiki.glidernet.org/wiki:prevent-sd-card-corruption
Prevent the write access which is the main cause for sd card corruption with OverlayFS