Merge pull request 'feat(upgrades): automate node reboots (kured) and wire Renovate, which had never run' (#73) from feat/automated-upgrades into main

Reviewed-on: #73
Reviewed-by: Keith Jackson <[email protected]>

infra/ansible/inventory/group_vars/k3s_prod/vars.yml

@@ -420,3 +420,34 @@ flux_bootstrap_env_path: "clusters/prod"
 # rather than leaving an inert drop-in behind, so this group-wide `true` is still correct
 # for it.
 etcd_io_priority_enabled: true
+
+# --- automatic security patching (roles/unattended_upgrades) -------------------------
+# TURNS ON roles/unattended_upgrades FOR PROD ONLY. Role default is false. Same seam as
+# node_baseline_backports_kernel and etcd_io_priority_enabled above.
+#
+# WHAT WAS THERE BEFORE: nothing at all. Measured on all three prod nodes 2026-10-17 —
+# `unattended-upgrades`, `update-notifier-common` and `needrestart` were ALL absent,
+# `apt-mark showhold` was empty on every node, /etc/apt/preferences.d/ was empty, and
+# nothing on the node could create /var/run/reboot-required. These boxes have had ZERO
+# automatic patching since provisioning, and no way to signal that a reboot was needed.
+#
+# WHAT ENABLING THIS DOES *NOT* DO: nothing, until the operator runs
+# playbooks/unattended-upgrades.yml. It is not applied by site.yml (deliberately — see
+# that playbook's header). And once run, it still never upgrades the KERNEL, never
+# restarts k3s, and never reboots:
+#   * kernel — blacklisted `^linux-`, AND the trixie-backports archive the running
+#     kernel comes from (o=Debian Backports, measured) is not an allowed origin. Two
+#     independent exclusions, because this is the EFI-memattr constraint: these HP minis
+#     need >= 6.13 or they can boot with a fraction of their RAM
+#     (PROD-PROVISIONING.md §0b), and 6.12 kernels are still installed and bootable here.
+#     The kernel continues to move ONLY under a deliberate
+#     `node-baseline.yml --tags kernel` run, exactly as before.
+#   * k3s — needrestart blacklist. k3s is not even an apt package on these nodes
+#     (measured: no `k3s`, no `containerd` in dpkg), so the control plane and runtime are
+#     outside apt's reach regardless.
+#   * reboots — Automatic-Reboot "false", asserted by the role against apt's own
+#     effective config. Reboots belong to kured (platform/kured): one node at a time,
+#     under a cluster-wide lock, inside 03:00-06:00, after cordon + drain. Three
+#     control-plane nodes with etcd quorum 2/3 must never reboot themselves
+#     independently, which is what Automatic-Reboot "true" would mean.
+unattended_upgrades_enabled: true

infra/ansible/playbooks/unattended-upgrades.yml

@@ -0,0 +1,36 @@
+---
+# Automatic Debian SECURITY patching for the k3s nodes — the package half of the automated upgrade
+# process. The reboot half is kured (platform/kured), reconciled by Flux; the two are designed
+# together and neither is useful alone. Full rationale for every decision:
+# roles/unattended_upgrades/defaults/main.yml and that role's README.md.
+#
+# TARGET (R-ENV-02): `k3s_hosts` defaults to dev's `k3s_servers`; prod is
+#   ansible-playbook playbooks/unattended-upgrades.yml -e k3s_hosts=k3s_prod
+# Same pattern node-baseline.yml and node-health.yml established — `hosts:` is templated before
+# group_vars exist, so the target is an extra var, never a group_vars value.
+#
+# The role is a NO-OP unless `unattended_upgrades_enabled` is true, which is set for prod only in
+# inventory/group_vars/k3s_prod/vars.yml. Running this against dev changes nothing.
+#
+# DELIBERATELY NOT IN site.yml. site.yml is the bring-up chain (node-baseline -> k3s ->
+# etcd-io-priority -> kube-vip -> cilium -> verify -> flux-bootstrap) and is "not run against prod
+# casually". Automatic patching is not a prerequisite for anything in that chain and nothing in the
+# chain depends on it, so adding it there would only widen what a cluster rebuild touches. It is
+# applied on its own, once, and re-applied when its configuration changes.
+#
+# SAFE TO RUN ON A LIVE CLUSTER, AT ANY TIME. This playbook installs and configures the upgrader. It
+# never runs `apt upgrade`, never restarts k3s, and never reboots — the role asserts the last of
+# those against apt's own effective config rather than trusting the file it just wrote. The first
+# unattended upgrade happens at the next timer firing (04:00 +/-60m), and any reboot that upgrade
+# implies is kured's to schedule, one node at a time, inside 03:00-06:00.
+#
+# TAGS. `--tags verify` re-runs only the read-only assertions and the per-node summary, which is the
+# way to answer "is automatic patching actually working on these boxes, and is anything waiting on a
+# reboot" without rewriting any configuration:
+#   ansible-playbook playbooks/unattended-upgrades.yml -e k3s_hosts=k3s_prod --tags verify
+- name: Automatic security upgrades on the k3s nodes (kernel excluded; reboots delegated to kured)
+  hosts: "{{ k3s_hosts | default('k3s_servers') }}"
+  become: true
+  gather_facts: true
+  roles:
+    - unattended_upgrades

infra/ansible/roles/unattended_upgrades/README.md

@@ -0,0 +1,184 @@
+# roles/unattended_upgrades
+
+Automatic Debian **security** patching on the k3s nodes. The kernel is excluded, k3s is never
+restarted, and reboots are delegated to **kured** (`platform/kured`).
+
+- **Playbook:** `playbooks/unattended-upgrades.yml`
+- **Enabled by:** `unattended_upgrades_enabled` — role default `false`, set `true` for prod in
+  `inventory/group_vars/k3s_prod/vars.yml`
+- **Companion component:** `platform/kured` (the reboot half). **Neither is useful alone** — see
+  "The two halves" below.
+- **Every decision and its reasoning:** `defaults/main.yml`. That file is the argument; this one is
+  the orientation.
+
+## The two halves, and why they ship together
+
+| | what it does | what it must NOT do |
+|---|---|---|
+| **this role** (Ansible, host) | installs security updates continuously; leaves `/var/run/reboot-required` behind when one needs a reboot | upgrade the kernel; restart k3s; reboot |
+| **kured** (Flux, cluster) | cordons, drains, reboots and uncordons **one node at a time** when that file exists | decide *whether* a reboot is needed |
+
+Deploying either alone produces a mechanism that looks healthy and does nothing:
+
+- **kured alone** watches a file that nothing creates. Measured 2026-10-17:
+  `update-notifier-common` — the package that owns the hook which writes
+  `/var/run/reboot-required` — was **not installed on any node**. kured would sit at 1/1 Running
+  reporting `kured_reboot_required=0` forever.
+- **this role alone** installs patches that a long-running process never picks up, and when a
+  reboot *is* needed there is nothing safe to take it. `Automatic-Reboot "true"` is not the
+  answer: three control-plane nodes with etcd quorum 2/3, each rebooting at its own time, is how
+  the cluster is lost.
+
+## What it was replacing: nothing
+
+Measured on all three prod nodes, 2026-10-17:
+
+| | |
+|---|---|
+| `unattended-upgrades` | **not installed** |
+| `update-notifier-common` | **not installed** |
+| `needrestart` | **not installed** |
+| `apt-mark showhold` | **empty** — no package held on any node |
+| `/etc/apt/preferences.d/` | **empty** — no apt pin declares the backports-kernel intent |
+| `/var/run/reboot-required` | absent, and uncreatable |
+
+These nodes had received **no automatic patching since provisioning**.
+
+## The three decisions
+
+### 1. Security only
+
+Allowed origins are `label=Debian-Security` and nothing else. `trixie-updates` is excluded
+deliberately (not overlooked) — it carries non-security fixes that are useful but are the archive
+through which an unreviewed change would most plausibly arrive on a control-plane node. The knob to
+add it is `unattended_upgrades_include_updates`.
+
+### 2. The kernel is excluded twice over
+
+**This is the highest-risk part of the change.** These HP EliteDesk 800 G5 minis publish a corrupt
+EFI Memory Attributes Table on R21 firmware; Linux `< 6.13` does not validate it before reserving
+memory from its contents, and `k3s-prod-2` twice booted with **2.6 GiB of 16 GB**. Upstream
+`8fbe4c49c0cc` (first in v6.13) is the only fix — there is no kernel cmdline workaround. Full
+write-up: `infra/PROD-PROVISIONING.md` §0b and `roles/node_baseline/defaults/main.yml:21-51`.
+
+Measured 2026-10-17: all three nodes run `7.1.8+deb13-amd64` (`7.1.8-1~bpo13+1`, i.e. the backports
+metapackage), comfortably above the floor — **but `linux-image-6.12.107+deb13-amd64` and
+`linux-image-6.12.94+deb13-amd64` are also still installed, below the floor, bootable, and held by
+nothing.**
+
+So an unattended process must not be able to touch the kernel at all:
+
+1. **Origin exclusion (structural).** The running kernel comes from `o=Debian Backports` (measured
+   via `apt-cache policy`, pin priority 100 — the `NotAutomatic` + `ButAutomaticUpgrades`
+   signature). That origin is not in `Origins-Pattern`, so unattended-upgrades cannot see a kernel
+   upgrade at all.
+2. **Package blacklist (belt and braces).** `^linux-` is blacklisted, so even if the origin list is
+   later widened — the most likely future edit to this role, and the one that would silently re-arm
+   the hazard — the kernel is still untouchable.
+
+The role **asserts both** against `apt-config dump` (apt's own parse of the whole
+`/etc/apt/apt.conf.d/` directory) rather than trusting the file it just wrote.
+
+**This does not stop the kernel moving.** The operator still advances it deliberately with
+
+```
+ansible-playbook playbooks/node-baseline.yml -e k3s_hosts=k3s_prod --tags kernel --limit <host>
+```
+
+which is the only thing that maintains the backports source, the metapackage and the on-node
+provenance stamp. `node_baseline`'s own note that `apt upgrade` keeps the backports kernel current
+still holds for an operator-run apt. What changed is that a **new unattended actor** is forbidden
+from it.
+
+Also blacklisted, for the same "operator-only" reason: `intel-microcode`, `amd64-microcode`,
+`grub-*`. Microcode and bootloader changes take effect on reboot and alter boot behaviour on the
+very firmware that is already misbehaving here.
+
+`Remove-Unused-Kernel-Packages` is **false**, against the Debian default: those older kernels are
+the documented rollback path, and an unattended process pruning them could remove the fallback an
+operator needs in front of a box that will not boot.
+
+### 3. needrestart restarts services — but never k3s
+
+A security-only policy that restarts nothing patches bytes on disk that no running process reads.
+`needrestart` in mode `a` restarts services still mapped to a deleted library, which is what makes
+the policy actually effective.
+
+`k3s.service` is blacklisted. Restarting the Kubernetes control plane unattended at 04:00 is a
+worse outcome than a delayed library fix; that fix lands at the next kured reboot instead. Measured
+2026-10-17, `k3s.service` is the **only** matching unit — k3s bundles its own containerd and
+kubelet, and neither `containerd` nor `containerd.io` is an apt package on these nodes — so this
+one entry is complete today.
+
+## Schedule
+
+`apt-daily` at 03:30 and `apt-daily-upgrade` at 04:00, both `±60m` randomised, via systemd drop-ins.
+Chosen to land **inside** kured's 03:00–06:00 reboot window so that a sentinel written by an upgrade
+can be acted on the same night rather than ~24h later.
+
+Two traps the role handles explicitly:
+
+- `/etc/apt/apt.conf.d/20auto-upgrades` must set the four `APT::Periodic::*` counters. Without
+  them the apt-daily timers fire and **do nothing** — installed, configured, green, and inert.
+- The timer drop-ins clear `OnCalendar=` before setting it. systemd **accumulates** `OnCalendar`
+  entries across drop-ins, so omitting the reset keeps the shipped schedule *in addition* to ours.
+
+## Why a new role rather than extending `node_baseline`
+
+`node_baseline` is the repo's only other apt surface and would have been a defensible home. Two
+reasons against:
+
+1. **Single responsibility.** `node_baseline` is the *first-boot floor* — it runs before k3s exists
+   and is the thing that makes a node installable. Continuous patching policy is a different
+   lifecycle with a different blast radius, and it wants to be runnable (and re-runnable) without
+   going anywhere near that role's data-disk tasks.
+2. **Concurrent work.** Other open branches touch `roles/node_baseline/`. A new role has nothing to
+   merge.
+
+Nothing here duplicates `node_baseline`: it does not add apt sources, does not touch the kernel, and
+does not manage disks.
+
+## Post-merge verification
+
+Running the role is safe on a live cluster at any time — it installs and configures the upgrader, and
+never runs `apt upgrade`, restarts k3s, or reboots.
+
+```bash
+# Apply (prod). Idempotent; re-runnable.
+cd infra/ansible && ansible-playbook playbooks/unattended-upgrades.yml -e k3s_hosts=k3s_prod
+
+# Re-run ONLY the read-only assertions + the per-node pending-reboot summary.
+cd infra/ansible && ansible-playbook playbooks/unattended-upgrades.yml -e k3s_hosts=k3s_prod --tags verify
+```
+
+Then, on a node, confirm the three properties that matter (all read-only, no sudo needed for the
+first two):
+
+```bash
+ssh [email protected] 'apt-config dump | grep -iE "unattended-upgrade::(automatic-reboot|package-blacklist|origins)"'
+ssh [email protected] 'systemctl list-timers apt-daily-upgrade.timer --no-pager'
+ssh [email protected] 'ls -la /var/run/reboot-required 2>&1; dpkg -l update-notifier-common needrestart unattended-upgrades | tail -4'
+```
+
+Expect: `Automatic-Reboot "false"`, a blacklist containing `^linux-`, an `Origins-Pattern`
+containing `Debian-Security` and **not** `Backports`, a next-elapse around 04:00, and all three
+packages `ii`.
+
+A dry run of what the upgrader would actually do (needs root, so this one is an operator step):
+
+```bash
+sudo unattended-upgrade --dry-run --debug
+```
+
+The kernel must appear in its blacklist output, not its upgrade list.
+
+## What this role cannot tell you
+
+- **That a security upgrade has ever succeeded.** That is in
+  `/var/log/unattended-upgrades/unattended-upgrades.log` on each node, and nothing in this repo or
+  in Prometheus reads it. There is no alert for "automatic patching has silently stopped working".
+  That is a real, known gap — see the handoff entry
+  `decisions/2026-10-17-automated-upgrades.md`.
+- **That a reboot actually happened.** That is kured's half, and it *is* alerted on
+  (`KuredRebootPending`, `KuredNodeCoverageGap`, `KuredNotReporting` in
+  `platform/kured/alerts.yaml`).

infra/ansible/roles/unattended_upgrades/defaults/main.yml

@@ -0,0 +1,172 @@
+---
+# roles/unattended_upgrades — automatic Debian SECURITY patching on the k3s nodes, with the kernel
+# deliberately excluded and with reboots delegated to kured (platform/kured).
+#
+# OFF BY DEFAULT, ON FOR PROD. Same seam as node_baseline_backports_kernel / etcd_io_priority_enabled:
+# a plain boolean, default false, turned on in inventory/group_vars/k3s_prod/vars.yml. Not a hostname
+# test — that would encode the environment into the role (see node_baseline's defaults for the full
+# argument, which this role follows rather than restates).
+#
+# ═════════════════════════════════════════════════════════════════════════════════════════════════
+# STATE BEFORE THIS ROLE (measured on all three prod nodes, 2026-10-17, via `dpkg-query -W`)
+# ═════════════════════════════════════════════════════════════════════════════════════════════════
+#   unattended-upgrades      NOT INSTALLED
+#   update-notifier-common   NOT INSTALLED
+#   needrestart              NOT INSTALLED
+#   apt-mark showhold        EMPTY (no package is held on any node)
+#   /var/run/reboot-required ABSENT, and nothing on the node can create it
+#   /etc/apt/preferences.d/  EMPTY (no apt pin declares the backports-kernel intent)
+# So: zero automatic patching, and no mechanism by which a reboot could ever be signalled. That last
+# point is why this role and platform/kured must land together — kured watches
+# /var/run/reboot-required, and on these nodes today NOTHING WRITES IT. Deploying kured alone would
+# produce a daemon that is permanently, silently idle while looking perfectly healthy.
+#
+# ═════════════════════════════════════════════════════════════════════════════════════════════════
+# DECISION 1 — SECURITY ONLY, NOT FULL UPGRADES
+# ═════════════════════════════════════════════════════════════════════════════════════════════════
+# Measured `apt-cache policy` on k3s-prod-1, 2026-10-17, gives the four archives and their pins:
+#   trixie            o=Debian,            a=stable,            l=Debian          pin 500
+#   trixie-updates    o=Debian,            a=stable-updates,    l=Debian          pin 500
+#   trixie-security   o=Debian,            a=stable-security,   l=Debian-Security pin 500
+#   trixie-backports  o=Debian Backports,  a=stable-backports,  l=Debian Backports pin 100
+#
+# Only `Debian-Security` is allowed below. The reasoning, in order of weight:
+#
+#   * Security updates are the class where the cost of NOT applying them is unbounded and the
+#     change itself is minimal by Debian policy (targeted fixes against the frozen stable version,
+#     no feature churn). It is the one class worth applying with nobody watching.
+#   * A full `apt upgrade` on these nodes would also pull trixie point-release changes, which is a
+#     larger surface than anyone has reviewed for a 3-node etcd cluster, for no urgency.
+#   * `trixie-updates` is DELIBERATELY EXCLUDED, not overlooked. It carries non-security fixes that
+#     are too urgent to wait for a point release — useful, but it is the archive through which an
+#     unreviewed change would most plausibly arrive, and it is not what "unattended" should mean on
+#     a control-plane node. Add it consciously later if the operator wants it; the knob is below.
+#   * `trixie-backports` is EXCLUDED, AND THAT IS THE KERNEL ARGUMENT — see DECISION 2.
+#
+# ═════════════════════════════════════════════════════════════════════════════════════════════════
+# DECISION 2 — THE KERNEL IS EXCLUDED TWICE OVER. THIS IS THE HIGHEST-RISK PART OF THE CHANGE.
+# ═════════════════════════════════════════════════════════════════════════════════════════════════
+# The constraint: HP's R21 firmware on these EliteDesk 800 G5 minis publishes a corrupt EFI Memory
+# Attributes Table, and Linux < 6.13 does not validate it before reserving memory from its contents
+# — k3s-prod-2 twice booted with 2.6 GiB of 16 GB. Upstream 8fbe4c49c0cc (first in v6.13) is the
+# ONLY fix; there is no kernel cmdline workaround. So these nodes run the backports metapackage
+# `linux-image-amd64` (measured 2026-10-17: version 7.1.8-1~bpo13+1 installed and running on all
+# three, well above the floor). Full write-up: infra/PROD-PROVISIONING.md §0b, and the rationale
+# block in roles/node_baseline/defaults/main.yml:21-51.
+#
+# A NODE THAT COMES BACK FROM AN UNATTENDED UPGRADE ON A 6.12 KERNEL IS A NODE THAT MAY COME BACK
+# WITH A FRACTION OF ITS RAM. Note that 6.12 kernels are not hypothetical here — measured
+# 2026-10-17, `linux-image-6.12.107+deb13-amd64` and `linux-image-6.12.94+deb13-amd64` are BOTH
+# still installed on all three nodes, below the floor, bootable, and nothing holds them.
+#
+# Two independent mechanisms keep unattended-upgrades away from the kernel, and the role asserts
+# both rather than trusting either:
+#
+#   1. ORIGIN EXCLUSION (structural). The running kernel comes from `o=Debian Backports`, which is
+#      not in Allowed-Origins. u-u only ever considers packages from allowed origins, so it cannot
+#      see a backports kernel upgrade at all. This also means the backports kernel receives no
+#      automatic patching — accepted, and in any case backports carries no security guarantees
+#      (node_baseline's defaults state that cost plainly: "no security-tracker commitment, no DSAs").
+#   2. PACKAGE BLACKLIST (belt and braces). `linux-*` is blacklisted below, so even if the origin
+#      list is later widened — the most likely future edit to this file, and the one that would
+#      silently re-arm the hazard — the kernel is still untouchable. Without this, widening origins
+#      to include backports would hand an unattended process the EFI-memattr-critical package.
+#
+# WHAT THIS DOES *NOT* DO, AND MUST NOT BE READ AS DOING: it does not stop the kernel moving. The
+# operator still advances it deliberately with
+#   ansible-playbook playbooks/node-baseline.yml -e k3s_hosts=k3s_prod --tags kernel --limit <host>
+# which is the only thing that maintains the backports source, the metapackage and the on-node
+# provenance stamp. node_baseline's own comment ("`ButAutomaticUpgrades: yes` ... means `apt upgrade`
+# keeps it current once installed") still holds for an operator-run apt; the measured pin priority of
+# 100 is exactly the NotAutomatic + ButAutomaticUpgrades signature that produces that behaviour.
+# Nothing here changes it. What changes is that a NEW unattended actor is forbidden from the kernel.
+#
+# NOT BLACKLISTED, BECAUSE THEY ARE NOT APT PACKAGES AT ALL — measured 2026-10-17: `dpkg-query` finds
+# no `k3s`, no `containerd` and no `containerd.io`. k3s is a single static binary at
+# /usr/local/bin/k3s installed by roles/k3s_server, and it bundles its own containerd and kubelet.
+# So the entire Kubernetes control plane and container runtime are OUTSIDE apt's reach and cannot be
+# upgraded by this role even in principle. That is worth knowing before worrying about it.
+unattended_upgrades_enabled: false
+
+# The packages this role installs. Each one is load-bearing; see the notes.
+unattended_upgrades_packages:
+  # The upgrader itself.
+  - unattended-upgrades
+  # THE SENTINEL WRITER, AND THE WHOLE REASON kured CAN WORK. On Debian, /var/run/reboot-required is
+  # not created by the kernel, by apt, or by unattended-upgrades — it is created by a hook shipped in
+  # update-notifier-common. Measured ABSENT on all three nodes. Without this package the file is
+  # never written, kured correctly never reboots, every dashboard stays green, and the reboot half of
+  # this PR is an elaborate no-op. The role asserts the hook exists after install rather than
+  # assuming the package shipped one (see tasks/main.yml).
+  - update-notifier-common
+  # Restarts services still mapped to a deleted library after a security upgrade. Without it a
+  # security-only policy patches bytes on disk that no running process reads — see DECISION 3.
+  - needrestart
+
+# --- Allowed origins -----------------------------------------------------------------------------
+# Verbatim apt origin expressions, substituted into 50unattended-upgrades. The ${distro_*} tokens
+# here are UNATTENDED-UPGRADES' OWN placeholders, expanded by it at runtime — they are not Ansible
+# or Flux substitutions, which is why they are single-quoted and why this role's files never travel
+# through Flux envsubst.
+#
+# `l=Debian-Security` plus the `-security` codename is the form Debian's own shipped config uses, and
+# both halves were confirmed against the measured archive metadata above (l=Debian-Security,
+# n=trixie-security). Matching on the LABEL rather than the suite name is what makes this survive the
+# next Debian release.
+unattended_upgrades_allowed_origins:
+  - 'origin=Debian,codename=${distro_codename},label=Debian-Security'
+  - 'origin=Debian,codename=${distro_codename}-security,label=Debian-Security'
+# Set this to add 'origin=Debian,codename=${distro_codename}-updates,label=Debian' — a deliberate
+# widening, kept as a knob so that turning it on is a reviewable one-line change rather than an edit
+# to a heredoc. See DECISION 1 for why it is off.
+unattended_upgrades_include_updates: false
+
+# --- Package blacklist ---------------------------------------------------------------------------
+# Regular expressions matched against package names. See DECISION 2: `linux-` is the EFI-memattr
+# guard and must not be removed without re-reading PROD-PROVISIONING.md §0b.
+unattended_upgrades_blacklist:
+  # Every kernel package: linux-image-*, linux-headers-*, linux-image-amd64 (the metapackage that
+  # actually tracks backports), plus linux-kbuild / linux-libc-dev. Anchored at the start so it
+  # cannot accidentally match an unrelated package containing the substring.
+  - '^linux-'
+  # Microcode changes take effect only on reboot and can alter boot behaviour on the very firmware
+  # that is already misbehaving here. Operator-only, same argument as the kernel.
+  - '^intel-microcode$'
+  - '^amd64-microcode$'
+  # The bootloader. A grub upgrade rewrites boot configuration on a machine with a documented
+  # warm-reboot hang (k3s-prod-2, 2026-09-03). Never unattended.
+  - '^grub-'
+  - '^grub2-common$'
+
+# --- Reboot policy -------------------------------------------------------------------------------
+# FALSE, AND THIS IS THE DIVISION OF LABOUR WITH kured, NOT AN OVERSIGHT.
+# unattended-upgrades can reboot a node itself (Automatic-Reboot "true"). It must not here: it has
+# no notion of a cluster, so it would not cordon, would not drain, would not evict the 25 attached
+# Longhorn volumes cleanly, would not check whether another node is already down, and — on three
+# control-plane nodes where etcd quorum is 2 of 3 — three nodes each deciding independently to
+# reboot at their own `Automatic-Reboot-Time` is precisely how you lose the cluster.
+# u-u therefore only ever leaves the sentinel behind; kured owns every reboot, one node at a time,
+# under a cluster-wide lock. See platform/kured/helmrelease.yaml.
+unattended_upgrades_automatic_reboot: false
+
+# --- needrestart (DECISION 3) --------------------------------------------------------------------
+# See the role README for the full argument. Summary: 'a' (restart services automatically) is what
+# makes a security-only policy actually effective — a patched libssl on disk does nothing for a
+# process still mapping the old one — but k3s.service is EXCLUDED, because restarting the
+# Kubernetes control plane unattended at 06:00 is a worse outcome than a delayed library fix.
+# Measured 2026-10-17: the only matching unit on these nodes is `k3s.service` (no separate
+# containerd or kubelet unit exists; k3s bundles both), so this blacklist is complete today.
+unattended_upgrades_needrestart_mode: a
+unattended_upgrades_needrestart_blacklist:
+  - '^k3s'
+
+# --- Schedule ------------------------------------------------------------------------------------
+# apt's own systemd timers (apt-daily, apt-daily-upgrade) drive u-u; these set their windows.
+# 04:00 with a 1h randomised delay, so the upgrade lands INSIDE kured's 03:00-06:00 reboot window
+# (platform/kured/helmrelease.yaml) rather than hours away from it: if an upgrade ever does set the
+# sentinel, the reboot can be taken the same night instead of waiting ~24h. The randomised delay
+# keeps the three nodes from hitting the mirror simultaneously; it does NOT serialise anything, and
+# it does not need to — u-u never reboots, so three concurrent upgrades are harmless.
+unattended_upgrades_download_time: "03:30"
+unattended_upgrades_upgrade_time: "04:00"
+unattended_upgrades_randomised_delay: 60m

infra/ansible/roles/unattended_upgrades/handlers/main.yml

@@ -0,0 +1,29 @@
+---
+# Re-arm apt's periodic timers after a config or drop-in change.
+#
+# WHY A daemon_reload IS REQUIRED AND NOT OPTIONAL. The timer windows are set by drop-ins under
+# /etc/systemd/system/apt-daily{,-upgrade}.timer.d/. systemd does not re-read unit files on its own,
+# so until it is told to, the RUNNING manager keeps the shipped schedule and the new window is
+# ignored — the files look right in git and on disk, `systemctl cat` shows them, and the upgrade
+# still fires at the old time. That is a silent config no-op, which is the failure mode this whole
+# role is written against.
+#
+# `daemon_reload` re-parses unit files and re-runs generators. It starts and stops nothing, so it
+# cannot disturb k3s, containerd or Longhorn — the same reasoning node_baseline's "Reload systemd
+# unit files" handler records.
+#
+# RESTARTING THE TIMERS IS ALSO SAFE, and is not the same as running the upgrade. `*.timer` units
+# only hold the schedule; restarting one recomputes its next elapse and does NOT trigger its
+# `*.service`. With `Persistent=true` set in the drop-in, a window missed while the node was down is
+# caught up on the next boot rather than skipped.
+#
+# Both fire only when a task actually changed, so a re-run of the role is silent.
+- name: Restart unattended-upgrades timers
+  ansible.builtin.systemd_service:
+    name: "{{ item }}"
+    state: restarted
+    enabled: true
+    daemon_reload: true
+  loop:
+    - apt-daily.timer
+    - apt-daily-upgrade.timer

infra/ansible/roles/unattended_upgrades/tasks/main.yml

@@ -0,0 +1,309 @@
+---
+# roles/unattended_upgrades — automatic Debian security patching, kernel excluded, reboots delegated
+# to kured. Every decision and its reasoning lives in defaults/main.yml; this file is the mechanism.
+#
+# TAGS — following roles/node_baseline, every task carries one of `packages`, `config` or `verify`.
+# An untagged run does all three in that order. The split exists because `verify` is the half an
+# operator will want to re-run on its own to answer "is automatic patching actually working on this
+# box", without re-writing any configuration:
+#   ansible-playbook playbooks/unattended-upgrades.yml -e k3s_hosts=k3s_prod --tags verify
+#
+# IT DOES NOT UPGRADE ANYTHING, AND IT DOES NOT REBOOT. This role installs and CONFIGURES the
+# upgrader; it never runs `apt upgrade` itself and never takes a reboot. Both of those are deliberate
+# and both follow roles/node_baseline/tasks/main.yml:61-67 ("IT DOES NOT REBOOT", after k3s-prod-2
+# hung on a warm reboot on 2026-09-03 and needed a physical power button). Applying this role is
+# therefore a SAFE operation on a live cluster at any time of day: the first unattended upgrade
+# happens at the next timer firing, and any reboot it implies is kured's to schedule inside the
+# 03:00-06:00 window.
+- name: Automatic security upgrades (unattended-upgrades; kernel excluded, reboots via kured)
+  when: unattended_upgrades_enabled | bool
+  tags: [packages, config, verify]
+  block:
+
+    # ── PREFLIGHT ───────────────────────────────────────────────────────────────────────────────
+    - name: Assert this is a Debian-family host
+      # The config file layout, the origin expressions and the package names below are all
+      # Debian-specific. On anything else this role would write files that are silently ignored,
+      # which is the failure mode this whole PR exists to avoid.
+      ansible.builtin.assert:
+        that:
+          - ansible_facts['os_family'] == 'Debian'
+        fail_msg: >-
+          REFUSING TO CONFIGURE unattended-upgrades on {{ inventory_hostname }}: os_family is
+          '{{ ansible_facts["os_family"] }}', not 'Debian'. The allowed-origin expressions and
+          config paths in this role are Debian-specific.
+      tags: [packages, config, verify]
+
+    # ── PACKAGES ────────────────────────────────────────────────────────────────────────────────
+    - name: Install unattended-upgrades, the reboot-sentinel writer and needrestart
+      # update-notifier-common is NOT optional padding: it owns the hook that creates
+      # /var/run/reboot-required, which is the only thing kured watches. See defaults/main.yml.
+      ansible.builtin.apt:
+        name: "{{ unattended_upgrades_packages }}"
+        state: present
+        update_cache: true
+        cache_valid_time: 3600
+      tags: [packages]
+
+    # ── CONFIG ──────────────────────────────────────────────────────────────────────────────────
+    # Written as a whole file rather than patched in place, for the reason node_baseline gives for
+    # its own apt source: an idempotent full-file write with a managed-by header is reviewable and
+    # re-runnable, whereas line-editing a conffile fights dpkg on every package upgrade.
+    #
+    # 52- RATHER THAN 50-: Debian ships /etc/apt/apt.conf.d/50unattended-upgrades as a CONFFILE of
+    # the unattended-upgrades package. Overwriting it would make every future apt upgrade of that
+    # package prompt about a locally-modified conffile (or, under the non-interactive defaults a
+    # scripted run uses, silently keep one side and discard the other). apt reads the directory in
+    # lexical order and later files win, so a separate 52- file overrides the shipped defaults
+    # without ever touching them, and `apt-config dump` in the verify block below proves which value
+    # actually won rather than assuming this ordering holds.
+    - name: Configure unattended-upgrades (52-k3s-unattended-upgrades)
+      ansible.builtin.copy:
+        dest: /etc/apt/apt.conf.d/52-k3s-unattended-upgrades
+        owner: root
+        group: root
+        mode: "0644"
+        content: |
+          // MANAGED BY ANSIBLE — infra/ansible/roles/unattended_upgrades. Local edits are reverted
+          // on the next run. Rationale for every value: that role's defaults/main.yml.
+          //
+          // Overrides the shipped 50unattended-upgrades by lexical ordering (52 > 50). The shipped
+          // file is a dpkg conffile and is deliberately left untouched.
+
+          // SECURITY ONLY. Deliberately excludes trixie-updates (non-security fixes) and
+          // trixie-backports (o=Debian Backports) -- and excluding backports is what makes it
+          // structurally impossible for this upgrader to move the EFI-memattr-critical kernel,
+          // which is installed from there. See defaults/main.yml DECISION 2.
+          Unattended-Upgrade::Origins-Pattern {
+          {% for origin in unattended_upgrades_allowed_origins %}
+                  "{{ origin }}";
+          {% endfor %}
+          {% if unattended_upgrades_include_updates | bool %}
+                  "origin=Debian,codename=${distro_codename}-updates,label=Debian";
+          {% endif %}
+          };
+
+          // NEVER AUTOMATICALLY UPGRADED, whatever the origin list later says. `^linux-` is the
+          // EFI-memattr guard: these HP minis need kernel >= 6.13 or they can boot with a fraction
+          // of their RAM, and 6.12 kernels are still installed and bootable on all three nodes.
+          // Do not remove without re-reading infra/PROD-PROVISIONING.md §0b.
+          Unattended-Upgrade::Package-Blacklist {
+          {% for pkg in unattended_upgrades_blacklist %}
+                  "{{ pkg }}";
+          {% endfor %}
+          };
+
+          // REBOOTS BELONG TO kured (platform/kured), NOT TO apt. All three nodes are
+          // control-plane + etcd with quorum 2 of 3, so three hosts independently deciding to
+          // reboot at their own Automatic-Reboot-Time is how the cluster is lost. u-u leaves
+          // /var/run/reboot-required behind; kured takes a cluster-wide lock and reboots exactly
+          // one node at a time, after cordon + drain, inside 03:00-06:00, gated on Longhorn volume
+          // health.
+          Unattended-Upgrade::Automatic-Reboot "{{ unattended_upgrades_automatic_reboot | bool | lower }}";
+          Unattended-Upgrade::Automatic-Reboot-WithUsers "false";
+
+          // Keep the node's disk from filling with superseded .debs, and keep a log an operator can
+          // read after the fact (/var/log/unattended-upgrades/). MinAge guards against removing a
+          // package still needed by a rollback.
+          Unattended-Upgrade::Remove-Unused-Kernel-Packages "false";
+          Unattended-Upgrade::Remove-New-Unused-Dependencies "true";
+          Unattended-Upgrade::Remove-Unused-Dependencies "false";
+          Unattended-Upgrade::AutoFixInterruptedDpkg "true";
+          Unattended-Upgrade::MinimalSteps "true";
+          Unattended-Upgrade::SyslogEnable "true";
+
+          // Remove-Unused-Kernel-Packages is FALSE on purpose, against the Debian default. These
+          // nodes deliberately carry more than one kernel: the backports kernel they boot and the
+          // distro kernels that are the documented rollback path (node_baseline writes the rollback
+          // procedure onto the node itself). An unattended process pruning kernels could remove the
+          // fallback an operator needs at 3am in front of a box that will not boot.
+      notify: Restart unattended-upgrades timers
+      tags: [config]
+
+    - name: Enable the apt periodic timers that actually run unattended-upgrades
+      # Installing the package is NOT sufficient to make it run on a schedule: without these
+      # counters apt's daily units do nothing, and the whole mechanism is inert while looking
+      # installed. `1` means "every day".
+      ansible.builtin.copy:
+        dest: /etc/apt/apt.conf.d/20auto-upgrades
+        owner: root
+        group: root
+        mode: "0644"
+        content: |
+          // MANAGED BY ANSIBLE — infra/ansible/roles/unattended_upgrades.
+          // Without these four counters the apt-daily timers fire and do nothing, so
+          // unattended-upgrades would be installed, configured, and never once invoked.
+          APT::Periodic::Update-Package-Lists "1";
+          APT::Periodic::Download-Upgradeable-Packages "1";
+          APT::Periodic::Unattended-Upgrade "1";
+          APT::Periodic::AutocleanInterval "7";
+      tags: [config]
+
+    - name: Ensure the systemd timer drop-in directories exist
+      # `copy` does not create parent directories, and these two .timer.d/ dirs do not exist on a
+      # stock Debian node — without this task the next task fails with "Destination directory does
+      # not exist" on a first run.
+      ansible.builtin.file:
+        path: "/etc/systemd/system/{{ item }}.timer.d"
+        state: directory
+        owner: root
+        group: root
+        mode: "0755"
+      loop:
+        - apt-daily
+        - apt-daily-upgrade
+      tags: [config]
+
+    - name: Pin the apt timer windows into kured's reboot window
+      # Overriding the shipped timers rather than editing them: a drop-in survives package upgrades.
+      # OnCalendar is cleared first (`OnCalendar=` with no value) because systemd ACCUMULATES
+      # OnCalendar entries across drop-ins — omit the reset and the unit keeps its shipped schedule
+      # IN ADDITION to ours, which would run the upgrade at both times and look like it worked.
+      ansible.builtin.copy:
+        dest: "/etc/systemd/system/{{ item.unit }}.timer.d/override.conf"
+        owner: root
+        group: root
+        mode: "0644"
+        content: |
+          # MANAGED BY ANSIBLE — infra/ansible/roles/unattended_upgrades.
+          # Lands the upgrade inside kured's 03:00-06:00 reboot window so a sentinel written by an
+          # upgrade can be acted on the same night rather than ~24h later.
+          [Timer]
+          OnCalendar=
+          OnCalendar={{ item.time }}
+          RandomizedDelaySec={{ unattended_upgrades_randomised_delay }}
+          Persistent=true
+        force: true
+      loop:
+        - { unit: apt-daily, time: "{{ unattended_upgrades_download_time }}" }
+        - { unit: apt-daily-upgrade, time: "{{ unattended_upgrades_upgrade_time }}" }
+      loop_control:
+        label: "{{ item.unit }} at {{ item.time }}"
+      notify: Restart unattended-upgrades timers
+      tags: [config]
+
+    - name: Configure needrestart (restart services, but never k3s)
+      # See defaults/main.yml DECISION 3. Auto-restart is what makes a security-only policy real --
+      # a patched library on disk does nothing for a process still mapping the deleted one -- but
+      # k3s.service is excluded because restarting the control plane unattended is worse than a
+      # delayed library fix. `$nrconf{restart}` is Perl config read by needrestart itself.
+      ansible.builtin.copy:
+        dest: /etc/needrestart/conf.d/50-k3s.conf
+        owner: root
+        group: root
+        mode: "0644"
+        content: |
+          # MANAGED BY ANSIBLE — infra/ansible/roles/unattended_upgrades.
+          # Restart mode: '{{ unattended_upgrades_needrestart_mode }}'  (a = automatically, l = list only, i = interactive)
+          $nrconf{restart} = '{{ unattended_upgrades_needrestart_mode }}';
+          # Units matching these patterns are NEVER restarted automatically. k3s bundles containerd
+          # and the kubelet, so this one entry covers the entire control plane and runtime on these
+          # nodes (measured 2026-10-17: k3s.service is the only matching unit). A library fix that
+          # needs k3s restarted therefore waits for the reboot kured will take.
+          $nrconf{blacklist_rc} = [
+          {% for pat in unattended_upgrades_needrestart_blacklist %}
+              qr({{ pat }}),
+          {% endfor %}
+          ];
+      tags: [config]
+
+    # ── VERIFY ──────────────────────────────────────────────────────────────────────────────────
+    # These tasks exist because every component of this mechanism fails SILENTLY. An installed
+    # package, a written config file and a green play are all compatible with nothing ever being
+    # upgraded and no reboot ever being signalled.
+
+    - name: Ask apt-config what the effective settings actually are
+      # `apt-config dump` is apt's OWN parse of the whole /etc/apt/apt.conf.d/ directory, so it
+      # proves what WON after lexical ordering rather than what this role wrote. If the shipped
+      # 50unattended-upgrades were ever renamed above 52-, this is the task that would catch it.
+      ansible.builtin.command: apt-config dump
+      register: unattended_upgrades_aptconfig
+      changed_when: false
+      check_mode: false
+      tags: [verify]
+
+    - name: Assert the kernel is blacklisted and automatic reboots are off
+      # The two properties that must never silently regress. Asserted against apt's own view.
+      ansible.builtin.assert:
+        that:
+          # apt-config renders each list entry as `Unattended-Upgrade::Package-Blacklist:: "^linux-";`
+          # so the anchored pattern itself is the thing to look for. Checking for the bare string
+          # `linux-` would pass on almost any dump and prove nothing.
+          - "'\"^linux-\"' in unattended_upgrades_aptconfig.stdout"
+          - "'Unattended-Upgrade::Automatic-Reboot \"false\"' in unattended_upgrades_aptconfig.stdout"
+          # The origin list must be non-empty, or u-u runs nightly and upgrades nothing — installed,
+          # scheduled, green, and inert.
+          - "'Debian-Security' in unattended_upgrades_aptconfig.stdout"
+        fail_msg: >-
+          EFFECTIVE apt CONFIG ON {{ inventory_hostname }} IS NOT WHAT THIS ROLE INTENDED.
+          Either the `^linux-` kernel blacklist or `Automatic-Reboot "false"` is not winning.
+          Both are safety properties, not preferences: without the blacklist an unattended process
+          can move a kernel these HP minis must keep >= 6.13 (PROD-PROVISIONING.md §0b), and
+          without Automatic-Reboot=false three control-plane nodes can each reboot themselves
+          independently and take etcd below quorum. Inspect with `apt-config dump | grep -i
+          unattended` and check for a file sorting after 52- in /etc/apt/apt.conf.d/.
+        success_msg: >-
+          Effective apt config confirmed: kernel blacklisted, automatic reboot disabled.
+      tags: [verify]
+
+    - name: Find the hooks that can create /var/run/reboot-required
+      # THE SENTINEL IS THE SINGLE POINT OF FAILURE FOR THE ENTIRE REBOOT HALF OF THIS DESIGN, and
+      # it is the one part that cannot be asserted from the repo — it depends on what
+      # update-notifier-common actually ships on this Debian release. Rather than hard-code a path
+      # that may not exist, discover the candidates and assert that at least one is present.
+      ansible.builtin.find:
+        paths:
+          - /etc/kernel/postinst.d
+          - /etc/apt/apt.conf.d
+        patterns:
+          - "*update-notifier*"
+          - "*unattended-upgrades*"
+          - "99update-notifier"
+        file_type: any
+      register: unattended_upgrades_sentinel_hooks
+      changed_when: false
+      tags: [verify]
+
+    - name: Assert something on this node can write the reboot sentinel
+      # If this fails, kured is a no-op: it watches /var/run/reboot-required forever, the file is
+      # never created, no reboot is ever taken, and NOTHING GOES RED -- the DaemonSet stays 1/1
+      # Running and `kured_reboot_required` reports a steady 0 on every node. That is the exact
+      # shape of failure (a check whose failure mode is a green tick) this repo has been burned by
+      # before, so it is an assert and not a debug message.
+      ansible.builtin.assert:
+        that:
+          - unattended_upgrades_sentinel_hooks.matched | int > 0
+        fail_msg: >-
+          NOTHING ON {{ inventory_hostname }} CAN CREATE /var/run/reboot-required. No
+          update-notifier / unattended-upgrades hook was found under /etc/kernel/postinst.d or
+          /etc/apt/apt.conf.d. kured watches that path and reboots only when it exists, so with no
+          writer the reboot automation is permanently and INVISIBLY idle -- kured stays 1/1 Running
+          and reports kured_reboot_required=0 on every node forever. Confirm
+          update-notifier-common is installed (`dpkg -l update-notifier-common`) and inspect
+          `dpkg -L update-notifier-common | grep -E 'postinst.d|apt.conf.d'`.
+        success_msg: >-
+          Reboot sentinel writer present ({{ unattended_upgrades_sentinel_hooks.matched }} hook(s)
+          found) -- a kernel or flagged package upgrade will signal kured.
+      tags: [verify]
+
+    - name: Report the pending-reboot state of this node
+      # Read-only. Tells the operator whether this node is currently waiting on kured for a reboot,
+      # which is the question `--tags verify` is usually being run to answer.
+      ansible.builtin.stat:
+        path: /var/run/reboot-required
+      register: unattended_upgrades_reboot_required
+      changed_when: false
+      tags: [verify]
+
+    - name: Summary
+      ansible.builtin.debug:
+        msg: >-
+          {{ inventory_hostname }}: security-only unattended upgrades ACTIVE
+          (upgrade timer {{ unattended_upgrades_upgrade_time }} +/-{{ unattended_upgrades_randomised_delay }}),
+          kernel and microcode blacklisted, automatic reboot DISABLED.
+          Reboot currently pending: {{ unattended_upgrades_reboot_required.stat.exists }}.
+          {% if unattended_upgrades_reboot_required.stat.exists %}
+          This node is waiting for kured to reboot it in the next 03:00-06:00 window; it will be
+          cordoned and drained first, and no other node will be rebooted at the same time.
+          {% endif %}
+      tags: [verify]