Rasperry Pi OS should keep previous kernel

[rkarlsba]

I just reported #217 and it seems to me that rpios is a bit too conservative on the disk usage. Currently, there doesn't seem to be a way to roll back to the previous kernel if the midden hits the windmill, so to say. It should be prominent to have a boot partition large enough to allow for at least two kernel versions in case the new one just doesn't work.

[lurch]

in case the new one just doesn't work

Mitigating against this, each new kernel-release goes through extensive testing before being pushed into the apt repo (that's what the use-at-your-own-risk rpi-update is all about), and the Raspberry Pi is fairly "fixed" from a hardware point of view.

[XECDesign]

The boot partition should currently be large enough. It's just that our kernel package isn't based on the one provided by Debian and isn't set up in a way that allows for multiple kernels.

But yes, ideally we should have a way to recover. I just can't think of one that doesn't involve taking the card out and manually fixing things on another computer, even if we do keep old kernels around.

Mitigating against this, each new kernel-release goes through extensive testing before being pushed into the apt repo (that's what the use-at-your-own-risk rpi-update is all about), and the Raspberry Pi is fairly "fixed" from a hardware point of view.

Things do slip through though. The linked issue is not something that would've been easy to spot in testing.

[lurch]

Things do slip through though. The linked issue is not something that would've been easy to spot in testing.

Yeah, but arguably "wifi not connecting" is something quite different to "the kernel not booting at all" :slightly_smiling_face: (although admittedly there's not much difference to the end-user if you're only connecting wirelessly to a headless Raspberry Pi)

[rkarlsba]

update at your own risk - heh - and here comes the next day zero bug ;)

[lurch]

Ahh, sorry if I wasn't clear in my description - it's only rpi-update that's "use at your own risk" (as noted in the documentation I linked to). rpi-update is where the pre-release kernels get tested, and only after they've gone through sufficient testing do they get labelled as a "stable" kernel and then pushed into apt. So most of the time, upgrading the kernel via apt upgrade shouldn't cause any problems.

[rkarlsba]

Appartently, #217 may not have been a kernel bug, but a bug in a dependency (regulatory.db). It still broke wifi, though (see the bug for details), so having the chance to just like in grub choose "last well know" or something would bevery practical

[lurch]

just like in grub choose "last well know"

On the RPi that might be possible with something like UBoot (?), but the way that Raspberry Pi OS works, the Linux kernel is the first thing that gets loaded by start.elf, so there's no mechanism to interactively select which kernel gets used. (more info here if you're curious, although note that on a Pi4 the job of bootcode.bin is instead done by the EEPROM bootloader)