The cutover is a switch, not a migration: unplug the USG, run one command, and
if anything is wrong run the other one and plug it back in. The operator will
have no internet during this and therefore no assistant, so the machinery has
to live on the boxes and the failure paths have to be proven in advance.
vyos-mode-delta.py generates the delta that turns the passive pair into the
gateway. Only one artifact is authored: gateway mode is always derived from
`load unifi.boot` + delta, so there is no inverse to maintain and no drift
between two hand-kept configs. It reuses unifi-to-vyos.py rather than
duplicating it, so what labsim proved and what production gets are one code
path. The PPPoE password is never written into the delta -- it carries a
placeholder the switch substitutes at apply time from /config/wan-secrets --
and generation fails if the real password appears in the output.
Two things the delta covers that the plan had underweighted:
- VyOS defaults to ACCEPT while the USG has an implicit WAN drop. Migrating
the port forwards alone would have left the router's own services and the
whole LAN reachable from the WAN. Added a stateful baseline scoped to the
WAN interface rather than a global default-action drop, so a mistake there
cannot lock anyone out over the LAN -- the only way back during a cutover.
- The old VIPs are NOT at network+254 on the /23 networks; they are
192.168.9.254, 10.0.9.254 and 10.0.1.254, in the upper half. A delete
naming a computed address fails quietly and leaves the group holding two
VIPs. The delta deletes the whole address node instead of guessing.
vyos-unifi-switch runs on the box from /config, which survives image upgrades,
so it works from a local terminal or the JetKVM with no workstation.
Proven on labsim, not assumed:
- unifi mode restores the previous config BYTE-EXACT (138 lines, diff clean).
- Auto-revert fires when the commit is not confirmed: 85 static-mappings ->
0, kea stopped, hostname restored, and uptime plus boot-id UNCHANGED, so
it reloaded rather than rebooted. That distinction is the whole reason
`commit-confirm action reload` is a prerequisite.
- Health-check failure triggers an immediate revert_soft rather than waiting
out the timer.
Four bugs found while doing it, each of which produced a wrong answer rather
than an error:
- commit-confirm is TWO steps. `config-mgmt commit_confirm` only arms the
revert timer; a normal `commit` still has to follow. Arming alone committed
nothing while reporting success.
- `sudo sg vyattacfg "config-mgmt ..."` loses the config-session environment,
so it reported "No configuration changes to commit" against a candidate
that plainly had 446 added lines.
- `... | grep -q` under `set -o pipefail` reports FAILURE on a match: grep
exits early, the producer takes SIGPIPE. Whether it triggers depends on
output size, so `status` misreported the mode intermittently.
- `show configuration commands` quotes values, so a fixed-string match for
`action reload` never matched `action 'reload'`.
CUTOVER.md is the printable runbook: both reachable addresses per box, the
escape hatch first, and the note that PPPoE is the one thing that could not be
tested beforehand.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DMVzWZgiKW2wquf5z8S1yH
d56bbf6db0