M1: Docker + single-node swarm via Nix (swarm-init + proxy overlay)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

BACKLOG.md

@@ -14,7 +14,8 @@ Two single-writer sections (§6.1): Builder edits only `## Build backlog`; Adver
       → CLAIMED 2026-05-26, awaiting Adversary (see STATUS.md)
 
 ### M1 — Swarm + abra target
-- [ ] Docker + single-node swarm via Nix
+- [x] Docker + single-node swarm via Nix (modules/swarm.nix: docker + swarm-init oneshot + `proxy`
+      overlay net + daily autoprune). Verified: Swarm=active, proxy overlay present.
 - [ ] Traefik (file provider → /var/lib/ci-certs/live/) + per-run wildcard router
 - [ ] abra installed; deploy + tear down a trivial recipe by hand over HTTPS
 - [ ] Gate: M1 — recipe reachable over HTTPS at *.ci.commoninternet.net, torn down clean

JOURNAL.md

@@ -97,3 +97,26 @@ with M1 (independent infra build), without advancing to M2 until M0 shows PASS.
 
 **Next:** M1 — Docker + single-node swarm via Nix (modules/swarm.nix), then Traefik (file provider
 → /var/lib/ci-certs/live/) + abra, then a by-hand HTTPS deploy/teardown of a trivial recipe.
+
+## 2026-05-26 — M1: Docker + single-node swarm via Nix
+
+**modules/swarm.nix:** `virtualisation.docker.enable` + daily autoprune (--all --volumes until=24h
+to protect the 28 GiB root), `docker` in systemPackages, and a `swarm-init` oneshot
+(`docker swarm init --advertise-addr 127.0.0.1` if not active; `docker network create --driver
+overlay --attachable proxy` if absent). Imported into configuration.nix.
+
+**Build + switch:** `nixos-rebuild build --flake .#cc-ci` → EXIT 0; `systemd-run … switch` →
+`Result=success`.
+
+**Verify (commands + output):**
+- `systemctl show swarm-init -p Result` → `Result=success`
+- `docker info --format ...` → `Swarm=active Managers=1 Nodes=1`
+- `docker network ls --filter name=proxy` → `proxy overlay swarm`
+- `systemctl is-system-running` → `running`; `--failed` → none.
+
+**Next:** Traefik as a swarm stack (Nix-declared compose + `docker stack deploy` oneshot): docker
+swarm provider + file provider serving /var/lib/ci-certs/live/{fullchain,privkey}.pem on :443,
+attached to `proxy`. Then abra install + by-hand HTTPS deploy/teardown of a trivial recipe (M1 gate).
+Rationale for swarm-service Traefik over a host `services.traefik`: a host process isn't on the
+`proxy` overlay, so it can't reach swarm service VIPs; coop-cloud recipes assume an on-`proxy`
+Traefik watching swarm labels.

STATUS.md

@@ -1,8 +1,9 @@
 # STATUS — cc-ci Builder
 
 **Phase:** M0 → M1. M0 complete & CLAIMED; starting M1 (swarm + Traefik + abra) while awaiting verdict.
-**In-flight:** M1 — Docker + single-node swarm via Nix (first M1 task).
+**In-flight:** M1 — Traefik next (file provider → /var/lib/ci-certs/live/, docker-swarm provider).
-**Last updated:** 2026-05-26 (M0 claimed)
+Docker + single-node swarm done.
+**Last updated:** 2026-05-26 (M1 swarm up)
 
 ## Gates
 - **Gate: M0 — CLAIMED, awaiting Adversary** (2026-05-26). Evidence: flake rebuilds cc-ci from repo

hosts/cc-ci/configuration.nix

@@ -6,6 +6,7 @@
   imports = [
     ./hardware.nix
     ../../modules/secrets.nix
+    ../../modules/swarm.nix
   ];
 
   # --- Tailscale (ACCESS-CRITICAL: do not break, this is the only route in) ---

modules/swarm.nix

@@ -0,0 +1,41 @@
+# Docker + single-node Swarm — the deploy target for recipes under test (M1).
+# Traefik (modules/traefik.nix) and abra layer on top; recipes attach to the `proxy`
+# overlay network, exactly as a real Co-op Cloud host expects.
+{ pkgs, ... }:
+{
+  virtualisation.docker = {
+    enable = true;
+    # Reclaim disk from churning per-run images/volumes (cc-ci root is ~28 GiB).
+    autoPrune = {
+      enable = true;
+      dates = "daily";
+      flags = [ "--all" "--volumes" "--filter" "until=24h" ];
+    };
+  };
+
+  environment.systemPackages = [ pkgs.docker ];
+
+  # Bring up a single-node swarm + the shared `proxy` overlay network. Idempotent:
+  # safe to re-run every boot/rebuild. advertise-addr 127.0.0.1 is fine for a lone node.
+  systemd.services.swarm-init = {
+    description = "Initialise single-node Docker Swarm + proxy overlay network";
+    after = [ "docker.service" ];
+    requires = [ "docker.service" ];
+    wantedBy = [ "multi-user.target" ];
+    path = [ pkgs.docker ];
+    serviceConfig = {
+      Type = "oneshot";
+      RemainAfterExit = true;
+    };
+    script = ''
+      set -eu
+      state="$(docker info --format '{{.Swarm.LocalNodeState}}' 2>/dev/null || echo error)"
+      if [ "$state" != "active" ]; then
+        docker swarm init --advertise-addr 127.0.0.1
+      fi
+      if ! docker network inspect proxy >/dev/null 2>&1; then
+        docker network create --driver overlay --attachable proxy
+      fi
+    '';
+  };
+}