update-initramfs produces a boot stub (~50 MB) that expects to mount a
separate rootfs over squashfs/disk/NFS. Our PXE channel only ships
vmlinuz+initrd.img, so the stub had nothing to pivot to — kernel
finished hand-off and the system wedged with firmware, modules, and
userspace stranded in the 545 MB rootfs dir we never delivered.
Replace with an everything-in-initramfs build: cpio.zst the full
rootfs (minus /boot) as the initrd, add /init -> sbin/init for the
kernel's runtime entrypoint, materialize the kernel symlink into a
real file. Bump check-initrd floor to 200 MB and switch the firmware
grep from unmkinitramfs (boot-stub-specific) to zstd | cpio -t.
Also add cpio to the CI apt deps.
josh
43ea845ac0