[Pkg-raspi-maintainers] Bug#996915: raspi-firmware: hook breaks label-based booting

[Cyril Brulebois]

Package: raspi-firmware
Version: 1.20210303+ds-2
Severity: important

Hi,

Building bullseye images using raspi-team/image-specs[1] for the Pi 4 B
or PI CM4 devices (`make raspi_4_bullseye.img`), I've been getting weird
things…

 1. https://salsa.debian.org/raspi-team/image-specs

Sometimes the boot would stop after a few seconds (last kernel log with
a timestamp around 6 seconds shown on HDMI), sometimes one would get a
prompt about a missing root filesystem, and be dropped inside an
initramfs prompt. (I've no certain answer at this point, but it seems
that the order of console= parameters in cmdline.txt might explain that
the prompt goes to the screen or the serial console; namely going to the
serial console during the first boot, and on screen for further boots,
due to the switched order after initial reconfiguration…)

Anyway, let's focus on the raspi-firmware issue:
 - image-specs generates a label-based booting, using this cmdline
   parameter: root=LABEL=RASPIROOT (similar to root=UUID=…).
 - The first boot ensures the raspi-firmware hook is called:
   /etc/kernel/postinst.d/z50-raspi-firmware
 - Running this hook results in the root= parameter's being replaced
   with the /dev/mmcblkNp2 du jour (it might be /dev/mmcblk0p2, it might
   be /dev/mmcblk1p2).
 - Further boots might see the same device come up with a different ID,
   leading to the root= vs. actual /dev/mmcblkNp2 mismatch that prevents
   booting.

In passing, the workaround in such cases is quite simple (when the
actual error messages are accessible, and one has access to a keyboard
or a serial console depending on cases):
 - symlink /dev/mmcblkXp2 to /dev/mmcblkYp2
 - exit the initramfs shell

and booting continues.


I think I'd prefer it if raspi-firmware wouldn't touch an existing root=
parameter. This would probably fix the very similar #984691 (about btrfs
booting).


Cheers,
-- 
Cyril Brulebois -- Debian Consultant @ DEBAMAX -- https://debamax.com/