After updating to bookworm enabling overlayfs via raspi-config seems to have changed its behaviour.
Before the update, it only affected the sd card filesystem but now it also changes my external usb drives into read-only. Is there any way to prevent this and make it only affect the SD card again? I'm a bit lost so any help would be appreciated.
After much hacking and googling on this:
raspi-config adds overlayroot=tmpfs in cmdline.txt to switch the overlayfs on.
If you change that to overlayroot=tmpfs:recurse=0 then the overlay file system will behave like before.
You can see all the options in /etc/overlayroot.conf
Also see:https://github.com/raspberrypi/bookworm-feedback/issues/137
update-initramfs: Generating /boot/initrd.img........when enabling the overlay. That message is no longer there and the system takes a while to reboot afterwards which makes me think the overlay is actually generated in the next boot if that makes any sense... I keep looking for any cluesoverlayfshas been around for a while, and offers promises of "good things"... But I get the feeling that it's not "ready for prime time". What do you think? A search suggests that it's not a well-understood subject here on RPi SE. And so you may be in "pioneer mode" - which may necessitate lots of trial-and-error on your part :)