systemd: the service manager as a module — holds node-service-manager and answers for the units in both scopes

The holder of the seat the controller seeds under novox/hq ADR 0177. Eight
verbs under the seat's name — units, status, start, stop, restart, enable,
disable, journal — each taking an optional scope, "system" by default or
"user" for the operator account's own manager, reached as
`systemctl --user --machine=<account>@` when the runtime is not that account.
One tool of its own, systemd_failed, for every failed unit in both scopes.
A package, a claim and a bundle; no container, no process: served by the node
tools runtime (ADR 0175) once it exists. `module check` passes against a
controller that carries the seat; the tools type-check against the SDK.

modules/systemd/client.ts

@@ -0,0 +1,93 @@
+// systemctl and journalctl, asked in one scope or the other (novox/hq ADR 0177).
+//
+// The system manager is the machine's. The user manager is the operator account's own: reached as
+// `systemctl --user --machine=<account>@` when this process is not that account (the node tools
+// runtime runs as the node's account, root when the host started it), and as plain `--user` when
+// it is. It answers only while the account's manager runs — a login, or lingering enabled.
+
+import { execFile } from "node:child_process";
+import { userInfo } from "node:os";
+
+export type Scope = "system" | "user";
+
+export interface Unit {
+  unit: string;
+  load: string;
+  active: string;
+  sub: string;
+  description: string;
+}
+
+function run(cmd: string, args: string[]): Promise<{ stdout: string; stderr: string; status: number }> {
+  return new Promise((resolve) => {
+    execFile(cmd, args, { maxBuffer: 8 * 1024 * 1024 }, (err, stdout, stderr) => {
+      const status = err && typeof (err as { code?: unknown }).code === "number" ? ((err as { code: number }).code) : err ? 1 : 0;
+      resolve({ stdout: String(stdout ?? ""), stderr: String(stderr ?? "") + (err && !(err as { code?: unknown }).code ? err.message : ""), status });
+    });
+  });
+}
+
+export class ServiceManager {
+  constructor(private readonly account: string) {}
+
+  static fromEnv(env: NodeJS.ProcessEnv): ServiceManager {
+    return new ServiceManager(env.MESH_OPERATOR_ACCOUNT?.trim() || userInfo().username);
+  }
+
+  /** The leading arguments that pick a manager. */
+  scopeArgs(scope: Scope): string[] {
+    if (scope !== "user") return [];
+    return userInfo().username === this.account ? ["--user"] : ["--user", `--machine=${this.account}@`];
+  }
+
+  async systemctl(scope: Scope, ...args: string[]): Promise<{ stdout: string; stderr: string; status: number }> {
+    return run("systemctl", [...this.scopeArgs(scope), ...args]);
+  }
+
+  async units(scope: Scope, pattern?: string): Promise<Unit[]> {
+    const args = ["list-units", "--all", "--no-legend", "--plain", "--no-pager"];
+    if (pattern) args.push(pattern);
+    const { stdout } = await this.systemctl(scope, ...args);
+    return stdout
+      .split("\n")
+      .map((l) => l.trim())
+      .filter(Boolean)
+      .map((l) => {
+        const [unit, load, active, sub, ...rest] = l.split(/\s+/);
+        return { unit, load, active, sub, description: rest.join(" ") };
+      });
+  }
+
+  async status(scope: Scope, unit: string): Promise<Record<string, string>> {
+    const props = ["LoadState", "ActiveState", "SubState", "UnitFileState", "MainPID", "ExecMainStatus", "Description", "FragmentPath"];
+    const { stdout } = await this.systemctl(scope, "show", unit, ...props.map((p) => `--property=${p}`));
+    const out: Record<string, string> = { unit, scope };
+    for (const line of stdout.split("\n")) {
+      const i = line.indexOf("=");
+      if (i > 0) out[line.slice(0, i)] = line.slice(i + 1);
+    }
+    return out;
+  }
+
+  async act(scope: Scope, verb: "start" | "stop" | "restart" | "enable" | "disable", unit: string): Promise<Record<string, unknown>> {
+    const { stderr, status } = await this.systemctl(scope, verb, unit);
+    const after = await this.status(scope, unit);
+    return { unit, scope, verb, ok: status === 0, stderr: stderr.trim(), active: after.ActiveState, boot: after.UnitFileState,
+      note: "a unit the mesh declares is restored to its declared state at the host's next apply" };
+  }
+
+  async journal(scope: Scope, unit: string, lines: number): Promise<{ unit: string; scope: Scope; lines: string[] }> {
+    const args = ["--no-pager", "-n", String(lines), "-u", unit, "-o", "short-iso"];
+    if (scope === "user") {
+      args.unshift(userInfo().username === this.account ? "--user" : `--machine=${this.account}@`, ...(userInfo().username === this.account ? [] : ["--user"]));
+    }
+    const { stdout } = await run("journalctl", args);
+    return { unit, scope, lines: stdout.split("\n").filter(Boolean) };
+  }
+
+  async failed(): Promise<{ system: Unit[]; user: Unit[] }> {
+    const system = (await this.units("system")).filter((u) => u.active === "failed");
+    const user = (await this.units("user").catch(() => [] as Unit[])).filter((u) => u.active === "failed");
+    return { system, user };
+  }
+}

modules/systemd/module.json

@@ -0,0 +1,46 @@
+{
+  "module": "systemd",
+  "version": "1",
+  "capabilities": [
+    "service-manager",
+    "package-manager"
+  ],
+  "claims": [
+    {
+      "name": "node-service-manager",
+      "scope": "node",
+      "serves": [
+        "units",
+        "status",
+        "start",
+        "stop",
+        "restart",
+        "enable",
+        "disable",
+        "journal"
+      ]
+    }
+  ],
+  "tools": [
+    "systemd_failed"
+  ],
+  "resources": [
+    {
+      "id": "package",
+      "type": "package",
+      "package": "systemd"
+    }
+  ],
+  "build": {
+    "artifacts": [
+      {
+        "name": "tools",
+        "kind": "bundle",
+        "language": "typescript",
+        "entrypoints": [
+          "tools/index.js"
+        ]
+      }
+    ]
+  }
+}

modules/systemd/package.json

@@ -0,0 +1,14 @@
+{
+  "name": "@novox/module-systemd",
+  "version": "0.1.0",
+  "description": "systemd \u2014 the machine's service manager as a module: holds node-service-manager and answers for the units in both scopes (novox/hq ADR 0177). The host applies units; this answers about them.",
+  "type": "module",
+  "private": true,
+  "dependencies": {
+    "@novox/mesh-sdk": "^0.1.0"
+  },
+  "devDependencies": {
+    "@types/node": "^22.0.0",
+    "typescript": "^5.6.0"
+  }
+}

modules/systemd/tools/index.ts

@@ -0,0 +1,71 @@
+// systemd's tools: the node-service-manager seat's eight verbs — the units on this machine in
+// both scopes, read and acted on by name — and the module's own reading of what has failed
+// (novox/hq ADR 0177). Served by the node tools runtime (ADR 0175); the host applies units, this
+// answers about them.
+import { registerModuleTools, type ToolDefinition } from "@novox/mesh-sdk/tools";
+import { ServiceManager, type Scope } from "../client.js";
+
+const scope = { type: "string", description: "\"system\" (the default) or \"user\": the operator account's own manager" };
+const unit = { type: "string", description: "the unit's name, as the service manager knows it" };
+
+function scopeOf(args: Readonly<Record<string, unknown>>): Scope {
+  const s = String(args.scope ?? "system");
+  if (s !== "system" && s !== "user") throw new Error(`scope ${JSON.stringify(s)}: "system" or "user"`);
+  return s;
+}
+function unitOf(args: Readonly<Record<string, unknown>>): string {
+  const u = String(args.unit ?? "").trim();
+  if (!u) throw new Error("a unit is required");
+  return u;
+}
+
+export function getSeatVerbs(manager: ServiceManager): ToolDefinition[] {
+  const act = (verb: "start" | "stop" | "restart" | "enable" | "disable", description: string): ToolDefinition => ({
+    name: verb,
+    description,
+    input: { type: "object", properties: { scope, unit }, required: ["unit"] },
+    run: async (args) => manager.act(scopeOf(args), verb, unitOf(args)),
+  });
+  return [
+    {
+      name: "units",
+      description: "The units the service manager knows in a scope, each with its load, active and sub state; narrowed to a pattern when asked.",
+      input: { type: "object", properties: { scope, pattern: { type: "string", description: "a glob the unit's name must match (optional)" } } },
+      run: async (args) => ({ scope: scopeOf(args), units: await manager.units(scopeOf(args), args.pattern ? String(args.pattern) : undefined) }),
+    },
+    {
+      name: "status",
+      description: "One unit as the service manager sees it now: its states, whether it starts at boot, its main process, and whether the mesh declares it.",
+      input: { type: "object", properties: { scope, unit }, required: ["unit"] },
+      run: async (args) => manager.status(scopeOf(args), unitOf(args)),
+    },
+    act("start", "Start one unit. For a unit the mesh declares, the answer says the host will restore what its declaration says at the next apply."),
+    act("stop", "Stop one unit; for a mesh-declared unit the answer says the host will restore its declared state."),
+    act("restart", "Restart one unit."),
+    act("enable", "Make one unit start at boot (or at the account's login, in user scope)."),
+    act("disable", "Stop one unit starting at boot (or at login, in user scope)."),
+    {
+      name: "journal",
+      description: "The last lines of one unit's journal.",
+      input: { type: "object", properties: { scope, unit, lines: { type: "number", description: "how many lines from the end (default 100)" } }, required: ["unit"] },
+      run: async (args) => {
+        const n = Number(args.lines ?? 100);
+        return manager.journal(scopeOf(args), unitOf(args), Number.isFinite(n) && n > 0 ? Math.min(n, 5000) : 100);
+      },
+    },
+  ];
+}
+
+export function getOwnTools(manager: ServiceManager): ToolDefinition[] {
+  return [
+    {
+      name: "systemd_failed",
+      description: "Every failed unit on this machine, in the system manager and in the operator account's.",
+      input: { type: "object", properties: {} },
+      run: async () => manager.failed(),
+    },
+  ];
+}
+
+registerModuleTools("node-service-manager", (env) => getSeatVerbs(ServiceManager.fromEnv(env)));
+registerModuleTools("systemd", (env) => getOwnTools(ServiceManager.fromEnv(env)));

modules/systemd/tsconfig.json

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+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "NodeNext",
+    "moduleResolution": "NodeNext",
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "noEmit": true
+  },
+  "include": [
+    "tools/index.ts",
+    "client.ts"
+  ]
+}