ArchLinux - mkinitcpio v38 upgrade

With the release of mkinitcpio v38, mkinitcpio hook migration and early microcode has been announced (04/03/2024). But how to migrate?

For a setup similar to mine, the steps are as follows.

Note: If it's already too late, and you can't boot anymore (blocked by a kernel panic), then this article will help you boot from an AL USB key and rescue your system.

First, upgrade the system. (it may fail at mkinitcpio stage, but we'll fix that)

pacman -Syu

Then, remove all kernel mkinitcpio presets because they contain old directives that will make mkinitcpio fail when trying to build initramfs.

rm /etc/mkinitcpio.d/linux*.preset

Then in order to re-generate new presets, we'll have to re-install kernel packages in order to trigger the pacman post-transaction hook that generates them.

pacman -S linux linux-lts linux-zen

Now let's edit mkinitcpio configuration (/etc/mkinitcpio.conf or a drop-in /etc/mkinitcpio.conf.d/hooks.conf) to add the new microcode hook:

-HOOKS=(base udev autodetect modconf kms keyboard keymap consolefont block encrypt lvm2 resume filesystems fsck)
+HOOKS=(base udev autodetect microcode modconf kms keyboard keymap consolefont block encrypt lvm2 resume filesystems fsck)

Now we can edit the bootloader configuration, e.g. for rEFInd /efi/EFI/arch/refind_linux.conf, and remove the microcode initrd that is no longer required as it's now packed together with the main initramfs image:

-"Boot with default options"  "cryptdevice=UUID=2fe657fa-3e5d-46db-9f2e-54529f96150e:cryptlvm initrd=\EFI\arch\amd-ucode.img root=/dev/myvg2/root rw initrd=\EFI\arch\initramfs-%v.img resume=/dev/myvg2/swap"
+"Boot with default options"  "cryptdevice=UUID=2fe657fa-3e5d-46db-9f2e-54529f96150e:cryptlvm root=/dev/myvg2/root rw initrd=\EFI\arch\initramfs-%v.img resume=/dev/myvg2/swap"

Finally, we can rebuild all initramfs images at once:

mkinitcpio -P

Reboot. You should have survived the mkinitcpio v38 released.