The role's `swapoff -a` + commented fstab line held only until the next boot,
on every prod node. Measured 2026-09-07: all three came back from a reboot with
977 MiB of swap ACTIVE (k3s-prod-1 /dev/sda4, k3s-prod-3 /dev/sda4, k3s-prod-2
/dev/nvme0n1p4) while their fstab swap entry was commented out by this role. The
role reported success and the setting silently expired.
CAUSE. systemd-gpt-auto-generator claims any GPT partition typed
0657fd6d-a4ab-43c4-84e5-0933c84b4f4f ("Linux swap") from the PARTITION TABLE,
synthesises a .swap unit into /run/systemd/generator.late/ and links it into
swap.target.wants/. It never reads /etc/fstab, so neutralising fstab cannot stop
it. Re-running the generator by hand on k3s-prod-1 says so verbatim:
Probed fstype 'swap' on partition /dev/disk/by-diskseq/1-part4.
Adding swap: /dev/disk/by-diskseq/1-part4
MECHANISM. Mask swap.target. `systemctl show` on the generated unit says its only
inbound dependency is `WantedBy=swap.target` — Requires/RequiredBy/BoundBy empty,
and the matching .device unit has an empty Wants=, so a device appearing does not
pull its swap unit in by itself. swap.target is the single choke point for every
activation path: gpt-auto, systemd-fstab-generator, systemd-cryptsetup-generator.
It is device-shape independent (no device name appears in the change, so one task
covers sda4, nvme0n1p4 and dev's vda VMs), boot-safe (swap.target is Wants=/After=
from sysinit.target and After= from tmp.mount; RequiredBy= is EMPTY on all three
prod and all three dev nodes, and a masked unit reached only via Wants= is skipped,
not failed), and inert if the device is absent or renamed. The generated units are
masked too, as a second independent barrier.
Rejected: `systemd.gpt_auto=0` (disables GPT auto-discovery wholesale, needs a GRUB
edit + reboot to become true, and on DEV would switch off root auto-discovery — dev's
vda1 carries the discoverable GUID 4f68bce3-e8cd-4db1-96e7-fbcaf984b709); clearing
the partition's GPT type GUID (a partition-table write to the live boot disk of a node
serving etcd and Longhorn replicas, and an irreversible decision about that 977 MiB
that belongs to the operator); `systemd.swap=0` (systemd-fstab-generator only — this
swap does not come from fstab).
`swapoff -a` is now conditional on `swapon --show` returning something, so the task
reports honestly instead of hiding a command that ran anyway behind changed_when: false.
PROVEN on k3s-prod-1 (all 18 Longhorn volumes healthy before the reboot):
run 1 changed=2, run 2 changed=0
after `reboot`: /proc/swaps empty, `free` Swap 0B, swap.target masked, the
generated unit still emitted by the generator and still masked, `systemctl
--failed` empty, `systemctl is-system-running` = running.
Co-Authored-By: Claude Opus 5 <[email protected]>
jakman85andClaude Opus 5
0e92d258dd