Everything but the reboot. Two rerunnable elway playbooks; the host is
still running from the ext4 root and its boot path is byte-identical to
the last 140 days, because grub-install is deliberately held back to the
cutover window.
Phase 1 (esh-pve-nas-stage-zfs-root.yaml): carve a 512 MB /boot LV out
of the 768 MB swap LV, populate it, rsync the 4.3 GB ext4 root into
nvme/ROOT/pve-1, write the copy's fstab.
Phase 2 (esh-pve-nas-stage-bootloader.yaml): ZFS initramfs, grub.cfg,
explicit pve-zfs-root and pve-ext4-rollback entries with stable ids,
grubenv pinned to the rollback so cutover's grub-reboot is a one-shot.
Three landmines the plan did not predict, all caught by verify steps
asserting effective state rather than by reading the plan:
- The /boot LV had nowhere to live. VG pve had 4 MB free and mounted
ext4 cannot shrink; freeing space from root needs a rescue boot, which
costs the one-reboot property. Space came from swap (768M -> 256M).
- The runbook's `zpool set cachefile=... nvme` would have broken the
NAS. Populating a cachefile flips the host from import-by-scan to
import-by-cache, so a one-pool cache leaves ssd and tank unimported --
and CT 103 esh-nas has twelve bind mounts spanning all three pools.
Set on all three instead, verified in the resulting cache.
- update-grub silently emitted a pool-less root=ZFS=/ROOT/pve-1, which
boots to an initramfs prompt. Debian's 10_linux builds ${rpool}${bootfs}
and rpool comes from grub-probe --target=fs_label, which returns empty
because GRUB's ZFS reader cannot open a pool with encryption,
large_dnode and zstd_compress -- the same feature set that forced /boot
to stay ext4. The probe failure is swallowed by `2>/dev/null || true`.
Fixed with a /etc/default/grub.d drop-in plus explicit menu entries.
The transferable lesson: the original verify grepped for the correct
root= string appearing somewhere in grub.cfg, which passes while every
menu entry is still broken. Assert the effective value, not the presence
of a substring.
vh
c4b2278e7d