Pi 5 Bookworm 64bit cannot set filesystem to read only

Support Raspberry Pi
1

Unable to make SD card filesystem read-only on PI5 with 64bit Bookworm OS.

  • tried using raspi-config…performance…overlay…and read-only boot settings. It doesnt work. I can still, for example, create a file on the desktop, and after reboot or power-up, the file remains. I have rebooted after setting the raspi-config settings, several times, before testing.

Am I missing something, or is this facility now broken? If broken, is there a work-around?

Thanks in advance for any help.

2

Hi @joseph256683

Welcome to the forum!

This comment thread on the Bookworm github might point you in the right direction for getting your issue sorted.

3

Hi Dan,

Unfortunately, that thread does not deal with the same issue. I have found that I can set the file system to read-only using the 32 bit OS, but not with the 64 bit OS.

Has anybody successfully implemented the read-only file system using the full 64 bit Bookworm OS using the prescribed rasppi-config settings?

4

Hey @joseph256683,

From what I can gather from that thread Dan shared, the file system not locking correctly is a known issue on more recent Pi OS versions. The method that involves changing settings using raspi-config still works but only to lock the root partition, not the user-accessible section of the SD card like the desktop.

It seems like the line overlayroot="tmpfs" in /etc/overlayroot.local.conf and overlayroot=tmpfs in /boot/cmdline.txt are responsible for controlling this behaviour although I couldn’t find a combination of settings for these values that successfully locked the file system on the most recent version of Bookworm on a Pi 5.

The cmdline.txt file has moved from /boot/cmdline.txt to /boot/firmware/cmdline.txt at some point between versions so this could be responsible for this problem in some way.

Hopefully someone else has more luck getting this to work.