latest Arch kernel/modules boot issue on my computer

[wiak]

Built a new WDL_Arch64 a week or so ago using new f_plugin - booted fine. Modified that plugin but slightly (to include a few alternative apps and remove some others) and built new WDL_Arch64 today. Odd... last week's fine, this week Kernel panic...

Known major dIfference: kernel/modules; last week's used kernel/modules version 5.12.15-arch1-1, the newest uses 5.13.5-arch1-1

Certainly the newest build works fine as long as I swap kernel/modules (in the initrd.gz and firstrib_rootfs) back to 5.12.15-arch1-1 and reboot.

However, may or may not be the kernel itself that is the problem. I note a major difference in packaging - Arch now providing the modules in compressed .zst form, previously used .xz

My latest build initrd.gz certainly seems to modprobe the main module list okay (watched via wd_debug grub kernel addition), but didn't find the boot partition so modules not loaded correctly actually (and also said (later in initrd/init script) that overlay module was 'wrong format' (that's when I checked and noticed zstd compressed). Not sure at the moment if the kernel is at fault (or somehow, but unlikely I feel, incompatible with my computer) - thought it might instead by busybox modprobe not being able to handle the .zst compressed module, but swapped the busybox.net one for the latest official arch static busybox and still same errors trying to boot with kernel/modules 5.13.5-arch1-1. The Arch Linux kernels have themselves supported zstd for some time. In the probably unlikely event Arch themselves have blundered in the xz to zstd format changeover for modules compression I'll wait a bit and see if any online reports (and probably try another new build next week). For now will just use the new build with the older kernel since working fine.

If no go, later I'll try using Arch's mkinitcpio (along with Arch's initrd special non-static busybox from mkinitcpio-busybox package) and experiment with simply using WDL init/w_init in there - may be a better way to do it anyway. EDIT: Actually, I'm looking into that alternative now, and yes, I think that is the likely issue - Arch's official initramfs uses kmod and not busybox modprobe and kmod includes zstd support. I'll try modifying that initramfs to use WDL init and w_init, which may prove to be a good solution.

[rockedge]

@wiak
I will also test this out. Interesting and glad you are looking into it!

[wiak]

@wiak
I will also test this out. Interesting and glad you are looking into it!

Though it may yet turn out to not be a zstd compressed modules issue, if it does, I expect similar issues may turn up in other distros since it looks likely that from kernel 5.13 onwards upstream packagers might all start releasing modules in that compressed format. At the moment I am not entirely sure about the issue - it was late last night so my quick fix attempts were not sufficient and I'm short of time at the moment otherwise I'd try an official Arch installation and see how there initramfs handles things - I'll do that sometime but other things I need to do non-computer related for the next few days. I don't know if busybox modprobe can handle zstd at the moment or not - no doubt busybox will cover that base later if needed anyway.

[wiak]

Per my PM to you @rockedge, WDL_Arch64 now booting and working fine with latest Arch Linux kernel 5.13.5.

As I suspected the issue was that the modules are now zstd compressed.

Now that I have it booting and working fine with a manually modified initrd.gz I'll be working on build_weedog_initramfs to automate the necessary changes for me. I suspect other distros will also eventually move to providing modules compressed in similar fashion, which may as I said cause some booting issues that these others will also need to address.

wiak

[wiak]

I have little doubt, that, assuming I don't need/want some extra lib functions from official Arch initramfs (via mkinitcpio) that it will be easier, and smaller build, to simply convert zstd compressed modules to other format for use inside the initramfs/initrd - smallest being uncompressed individually, but then whole lot compressed in one go with say xz in this case. Main rootfs can just keep them as zstd compressed however (since makes upgrading them easier). Otherwise, I currently need to patch current build_weedog_initrd-created WDL initrd with several extra libs; no big deal though - doing that does work, and probably simplest to do.