Support for read-only partitions

[terra-yuri]

Hi,

Will this work seamlessly if the boot/system partitions are read-only (as in, in the input OS image they are set to ro in fstab), or is there any part in the workflow that requires it to be r/w?

Thank you!

[tdewey-rpi]

I think this will depend on your mounting scheme.

Currently, rpi-sb-provisioner assumes you're using a vfat + ext4 partition layout - which is the standard image pi-gen produces. If you are performing a read-only remount as part of Init, I can't see a problem.

However, if you're using a different filesystem, or are expecting the fstab parsing to handle the initial mount & pivot from the initramfs, then I think you're in for a surprise. The pre-boot authentication image does not mount the rootfs as readonly - though we could explore adding support if the early-boot remount-readonly is unviable.

[terra-yuri]

Thank you for the response.

If my mounting scheme is to setup read only mode by including "ro" in /boot/cmdline.txt as well as setting it up in /etc/fstab for / and /boot - is it expected to work?

In case the answer is no, can you please elaborate on how to achieve a read-only rebound as part of init (where it is expected to work)?