Pin compose example to v0.1.6

A zero-argument invocation now shows the usage text when stdout is a
console (double-clicked exe, interactive shell). Without a terminal —
Docker entrypoint, services, pipes — a bare invocation still starts the
proxy, so the container image and service behavior are unchanged.

.gitea/workflows/ci.yml

@@ -80,8 +80,12 @@ jobs:
             -o gpu-turnstile.exe ./cmd/gpu-turnstile
 
       - name: Sign and checksum
+        env:
+          RELEASE_SIGNING_KEY: ${{ secrets.RELEASE_SIGNING_KEY }}
         run: |
-          printf '%s\n' "${{ secrets.RELEASE_SIGNING_KEY }}" > key.pem
+          # The key comes via the environment so its value never appears in
+          # the echoed command line of the run log.
+          printf '%s\n' "$RELEASE_SIGNING_KEY" > key.pem
           chmod 600 key.pem
           openssl pkeyutl -sign -inkey key.pem -rawin \
             -in gpu-turnstile.exe -out gpu-turnstile.exe.sig

Dockerfile

@@ -1,6 +1,6 @@
 FROM golang:1.23 AS build
 WORKDIR /src
-COPY go.mod ./
+COPY go.mod go.sum ./
 COPY cmd ./cmd
 COPY internal ./internal
 ARG VERSION=dev

README.md

@@ -29,6 +29,12 @@ Open WebUI / n8n ────► :8188  ───┘
 - Everything else (including websockets and all streaming) passes through
   transparently and unbuffered.
 
+Each consumer is enabled by setting its URL (`OLLAMA_URL`, `COMFY_URL`) and
+disabled by leaving it empty — at least one is required. With only Ollama
+the proxy is a pass-through (no image jobs can arrive); with only ComfyUI
+the Ollama unload/warm steps are skipped. Future consumers (e.g. local game
+detection) plug into the same lock the same way.
+
 ## Configuration
 
 Configuration comes from environment variables and/or an `.env`-style
@@ -41,8 +47,8 @@ override file values. Invalid values fail at startup.
 |---|---|---|
 | `LISTEN_OLLAMA` | `:11434` | Ollama-facing listener |
 | `LISTEN_COMFY` | `:8188` | ComfyUI-facing listener |
-| `OLLAMA_URL` | `http://127.0.0.1:11435` | Ollama upstream |
+| `OLLAMA_URL` | _(empty = disabled)_ | Ollama upstream; set to enable the Ollama consumer |
-| `COMFY_URL` | `http://127.0.0.1:8189` | ComfyUI upstream |
+| `COMFY_URL` | _(empty = disabled)_ | ComfyUI upstream; set to enable the ComfyUI consumer |
 | `UNLOAD_TIMEOUT` | `60s` | Wait for Ollama to unload before an image job |
 | `JOB_TIMEOUT` | `15m` | Wait for a ComfyUI job to finish |
 | `LLM_WAIT_TIMEOUT` | `10m` | Max lock wait for an LLM request before 503 (wait mode) |
@@ -70,7 +76,7 @@ override file values. Invalid values fail at startup.
 ## Observability
 
 - `GET /healthz` (both listeners): `{"state":"idle|llm|image","llm_inflight":N,"image_pending":B}`
-- `GET /metrics` (Ollama listener): Prometheus text format — `gpu_turnstile_state`,
+- `GET /metrics` (both listeners): Prometheus text format — `gpu_turnstile_state`,
   `gpu_turnstile_llm_inflight`, `gpu_turnstile_image_pending`,
   `gpu_turnstile_image_jobs_total`, `gpu_turnstile_lock_wait_seconds`
   (histogram, `kind="llm|image"`), `gpu_turnstile_unload_seconds`.
@@ -85,29 +91,54 @@ override file values. Invalid values fail at startup.
 
 ```sh
 go build ./cmd/gpu-turnstile
-./gpu-turnstile
+OLLAMA_URL=http://127.0.0.1:11435 COMFY_URL=http://127.0.0.1:8189 ./gpu-turnstile
 ```
 
-### Run natively on Windows (primary deployment)
+Running the binary with no arguments in a terminal prints the help screen
+(same as `-h`/`--help`); without a terminal (services, containers) a bare
+invocation starts the proxy.
 
-Download `gpu-turnstile.exe` from a release, put a `gpu-turnstile.env`
+### Run natively on Windows (current primary deployment)
-next to it, and run it — or install it as a Windows service from an
+
-elevated shell:
+Download `gpu-turnstile.exe` from a release and install it as a Windows
+service — no admin shell needed, a UAC prompt appears automatically and
+the elevated child does the work (its window waits for Enter so you can
+read the result):
 
 ```sh
-gpu-turnstile.exe service install          # auto-start service, recovery = restart
+gpu-turnstile.exe --install-service        # installs into Program Files, auto-start
-gpu-turnstile.exe service remove
+gpu-turnstile.exe --install-service --no-copy   # register in place instead
+gpu-turnstile.exe --remove-service
 ```
 
-The service uses the config file (services have no convenient
+Layout: `C:\Program Files\gpu-turnstile\` holds the exe and
-environment); set `LOG_FILE` in it since there is no console.
+`gpu-turnstile.env`, logs go to `C:\ProgramData\gpu-turnstile\` (set
+`LOG_FILE` in the env file — there is no console). The service always runs
+as the virtual account `NT SERVICE\gpu-turnstile` (low-privilege,
+per-service, no password); the installer automatically grants it write
+access to the install and data directories — nothing else to do.
 
-Suggested layout: `C:\Program Files\gpu-turnstile\` for the exe and
+### Run natively on Linux (systemd)
-`gpu-turnstile.env`, logs under `C:\ProgramData\gpu-turnstile\` via
+
-`LOG_FILE`. The service runs as `LocalSystem` by default, which can write
+The same binary works on Linux. Install it as a systemd service as root:
-the install directory for self-updates. For least privilege, run it as the
+
-virtual account `NT SERVICE\gpu-turnstile` and grant write access to just
+```sh
-those two directories.
+gpu-turnstile --install-service            # installs into /var/lib/gpu-turnstile, enables + starts
+gpu-turnstile --install-service --no-copy  # register in place instead
+gpu-turnstile --remove-service
+```
+
+The unit (`/etc/systemd/system/gpu-turnstile.service`) is `Type=notify`:
+`systemctl start` blocks until the listeners are actually bound, a 30 s
+watchdog restarts the process if it wedges, and logs land in the journal
+(`journalctl -u gpu-turnstile -f`) unless `LOG_FILE` is set. Install
+copies the binary to `/var/lib/gpu-turnstile/` and the config to
+`/etc/gpu-turnstile.env` (edit that one after installing). The service
+runs sandboxed with `DynamicUser=yes` — a transient low-privilege UID,
+read-only filesystem except its install dir (so self-update keeps
+working), no capabilities, syscall-filtered: same least-privilege idea as
+the Windows virtual account. The notify integration is a no-op in
+containers and interactive shells.
 
 **Auto-update is on by default**: the binary checks the repo's latest
 release on startup and every `UPDATE_INTERVAL`, verifies the Ed25519
@@ -118,6 +149,8 @@ OpenSSL; the matching public key lives in `internal/update/pubkey.go`
 (one-time setup: `openssl genpkey -algorithm ed25519 -out private.pem`,
 `openssl pkey -in private.pem -pubout -out public.pem`; private key goes
 to the `RELEASE_SIGNING_KEY` repo secret, public key is committed).
+`gpu-turnstile --force-update` checks immediately, stages the new binary
+and restarts the running service (elevating via UAC only if needed).
 
 ### Docker
 

SPEC.md

@@ -42,6 +42,21 @@ listener is an `httputil.ReverseProxy` to its upstream. Websocket upgrades
 (ComfyUI `/ws`) and streaming bodies (Ollama NDJSON / SSE) must pass through
 unbuffered (`FlushInterval = -1`).
 
+### Modes of operation
+
+Each GPU consumer is enabled by setting its URL and disabled by leaving it
+empty — no separate flags. At least one URL must be set; a disabled
+consumer gets no listener, no startup probe, and no lock participation:
+
+- **Both set** (default deployment): full arbitration as described below.
+- **Only `OLLAMA_URL`**: pure pass-through for Ollama; the LLM lock never
+  blocks since no image jobs can arrive.
+- **Only `COMFY_URL`**: image jobs are tracked and ComfyUI's VRAM is freed
+  afterwards, but the Ollama unload and warm-reload steps are skipped.
+- Future consumers (e.g. detecting a local game holding VRAM) plug into the
+  same lock the same way: enabled by their config knob, excluded when
+  absent.
+
 ### Lock semantics
 
 Two-mode lock with image priority (writer-preferring RW lock, where "readers"
@@ -83,7 +98,8 @@ ComfyUI listener (`:8188` → `COMFY_URL`):
 ### Image job flow (`POST /prompt`)
 
 1. `AcquireImage()`.
-2. Unload Ollama: `GET /api/ps`; for each model `POST /api/generate
+2. Unload Ollama (skipped when `OLLAMA_URL` is unset): `GET /api/ps`; for
+   each model `POST /api/generate
    {"model":M,"keep_alive":0}`; if that returns non-2xx (embedding-only
    models), `POST /api/embed {"model":M,"input":"x","keep_alive":0}`. Poll
    `/api/ps` every `UNLOAD_POLL_INTERVAL` (default 500 ms) until empty or
@@ -117,8 +133,8 @@ override file values. A missing file is fine; a malformed one is fatal.
 |---|---|---|
 | `LISTEN_OLLAMA` | `:11434` | Ollama-facing listener |
 | `LISTEN_COMFY` | `:8188` | ComfyUI-facing listener |
-| `OLLAMA_URL` | `http://127.0.0.1:11435` | upstream |
+| `OLLAMA_URL` | _(empty = disabled)_ | Ollama upstream; set to enable the Ollama consumer |
-| `COMFY_URL` | `http://127.0.0.1:8189` | upstream |
+| `COMFY_URL` | _(empty = disabled)_ | ComfyUI upstream; set to enable the ComfyUI consumer |
 | `UNLOAD_TIMEOUT` | `60s` | wait for Ollama to unload |
 | `JOB_TIMEOUT` | `15m` | wait for ComfyUI job |
 | `LLM_WAIT_TIMEOUT` | `10m` | max time an LLM request waits for the lock before 503 (wait mode) |
@@ -143,28 +159,84 @@ override file values. A missing file is fine; a malformed one is fatal.
 | `UPDATE_REPO` | `https://git.rambossek.at/PUBLIC/gpu-turnstile` | repository to check for releases |
 | `UPDATE_ASSET` | `gpu-turnstile.exe` | release asset to download |
 
-Startup fails fast on unparsable values. Both upstreams are probed once at
+Startup fails fast on unparsable values and when neither consumer URL is
-start (`/api/version`, `/system_stats`); failure is logged, not fatal.
+set. Enabled upstreams are probed once at start (`/api/version`,
+`/system_stats`); failure is logged, not fatal.
 
-## Native Windows deployment
+## Native deployment (Windows and Linux)
 
-The binary runs natively on Windows (the primary deployment) as well as in
+The binary runs natively on Windows (the current primary deployment) and on
-Docker.
+Linux with systemd (the future GPU server), as well as in Docker.
 
-- `gpu-turnstile.exe service install [-config path]` registers an
+Service management is the same on both platforms:
-  auto-start Windows service (needs an elevated shell). Recovery actions
+`gpu-turnstile --install-service [-config path]` installs, registers and
-  restart it 5 s after any failure. `service remove` uninstalls.
+starts an auto-start service; `--remove-service` stops and uninstalls it.
-- **Layout**: install to `C:\Program Files\gpu-turnstile\` (exe plus
+Both need admin/root; on Windows a non-elevated shell triggers a UAC
-  `gpu-turnstile.env`); logs belong in `C:\ProgramData\gpu-turnstile\` via
+prompt instead of failing — the command relaunches itself elevated, waits
-  `LOG_FILE`. The service must be able to write its install directory for
+for the child, and mirrors its exit code. The legacy form
-  self-updates — Program Files is writable by LocalSystem and admins, which
+`gpu-turnstile service install|remove` does the same thing.
-  is why running as the default `LocalSystem` account is the simple choice.
+
-- **Account**: the default `LocalSystem` works out of the box. For least
+By default install creates the canonical layout and copies the binary into
-  privilege, create the service with the virtual account
+it (Windows: `%ProgramFiles%\gpu-turnstile\`, plus
-  `NT SERVICE\gpu-turnstile` and grant it write access to the install and
+`%ProgramData%\gpu-turnstile\` for logs; Linux: `/var/lib/gpu-turnstile/`
-  log directories only (no network logon, no user profile).
+with the config at `/etc/gpu-turnstile.env`). An existing config in the
-- Use a config file (above) for the service — Windows services have no
+target location is never overwritten. `--no-copy` registers the current
-  convenient environment. Logs go to `LOG_FILE` since there is no console.
+executable location as-is instead.
+
+### Windows
+
+- `--install-service` creates `%ProgramFiles%\gpu-turnstile\` and
+  `%ProgramData%\gpu-turnstile\`, copies the exe and (if none exists there
+  yet) the `gpu-turnstile.env` into the Program Files directory, and
+  registers that copy as a Windows service; recovery actions restart it
+  5 s after any failure. Logs go to the ProgramData directory via
+  `LOG_FILE` since there is no console.
+- **Account**: the service always runs as the virtual account
+  `NT SERVICE\gpu-turnstile` — a per-service low-privilege identity the
+  SCM manages (no password, automatic logon-as-a-service right, no admin
+  rights, gone when the service is removed). The installer grants it
+  modify access to the install and data directories (self-updates rewrite
+  the exe) and the `LOG_FILE` directory (created if missing), plus read
+  access to the config file when it lives elsewhere. The grants happen
+  after service registration because the virtual account's SID only exists
+  from that point on; if a grant fails the service registration is rolled
+  back.
+
+### Linux (systemd)
+
+- `--install-service` copies the binary to `/var/lib/gpu-turnstile/`,
+  copies the config to `/etc/gpu-turnstile.env` if none exists there yet,
+  writes `/etc/systemd/system/gpu-turnstile.service`, then runs `systemctl
+  daemon-reload` and `enable --now`. `--remove-service` removes the unit
+  and the installed binary; the `/etc` config stays. The binary does not
+  go to `/usr/local/sbin` on purpose: replacing a running binary needs
+  write access to its *directory*, and granting the sandboxed service
+  write access to a shared system directory would let a compromised
+  service overwrite other binaries — `/var/lib/gpu-turnstile` is
+  exclusively ours.
+- **Sandboxing** mirrors the Windows virtual account: the unit runs with
+  `DynamicUser=yes` — a transient per-service UID with no login, no home
+  and no password, managed entirely by systemd. `ProtectSystem=strict`
+  makes the filesystem read-only except `StateDirectory=gpu-turnstile`
+  (the install dir, so self-updates can rewrite the binary), plus
+  `NoNewPrivileges`, `ProtectHome`, `PrivateTmp`, `ProtectKernel*`,
+  `ProtectControlGroups`, `RestrictNamespaces`, `RestrictSUIDSGID`,
+  `RestrictRealtime`, `LockPersonality`, `MemoryDenyWriteExecute`, empty
+  capability sets, `RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6` and
+  `SystemCallFilter=@system-service`. The proxy needs only outbound
+  TCP/UDP and the notify socket, so it loses nothing.
+- The unit is `Type=notify`: the binary sends `READY=1` via
+  `github.com/coreos/go-systemd` only after the listeners are bound, so
+  `systemctl start` blocks until the proxy accepts connections. A 30 s
+  watchdog (`WatchdogSec=`) is pinged as long as the process runs; three
+  missed pings make systemd restart it. `STOPPING=1` is sent on shutdown.
+  All notify calls are no-ops when `NOTIFY_SOCKET` is unset (containers,
+  interactive shells), and the whole integration is Linux-only — Windows
+  builds carry no-op stubs.
+- Logs go to the journal (`journalctl -u gpu-turnstile`) or to `LOG_FILE`.
+- **Auto-update** works the same as on Windows: `Restart=on-failure` with
+  `RestartSec=5s` brings up the staged binary after the updater exits with
+  code 3.
 - **Auto-update**: on startup and every `UPDATE_INTERVAL`, the binary
   checks `UPDATE_REPO`'s latest release; if its tag is a newer `vX.Y.Z`,
   it downloads `UPDATE_ASSET` plus its `.sig` (and `.sha256` when present)
@@ -174,6 +246,11 @@ Docker.
   idle the process exits with code 3 so the service recovery restarts it
   on the new version. Interactive runs only log "restart to apply".
   `dev` builds and builds without an embedded public key never update.
+- **`--force-update`** runs the same check immediately: it downloads,
+  verifies and stages a newer release, and if the service is running it
+  restarts it right away (otherwise the new version applies on next
+  start). On Windows it elevates via UAC only when the stage or restart
+  needs permissions the caller does not have.
 - **Signing setup (one time)**: `openssl genpkey -algorithm ed25519 -out
   private.pem`; `openssl pkey -in private.pem -pubout -out public.pem`.
   Private key → repo secret `RELEASE_SIGNING_KEY`; public key → committed into
@@ -184,7 +261,7 @@ Docker.
 
 - `GET /healthz` on both listeners: 200 with JSON
   `{"state":"idle|llm|image","llm_inflight":N,"image_pending":B}`.
-- `GET /metrics` on the Ollama listener: Prometheus text format, no external
+- `GET /metrics` on both listeners: Prometheus text format, no external
   dependency needed:
   `gpu_turnstile_state{state="…"} 1`, `gpu_turnstile_llm_inflight`,
   `gpu_turnstile_image_jobs_total`, `gpu_turnstile_lock_wait_seconds`
@@ -233,7 +310,7 @@ gpu-turnstile/
   internal/metrics/          # Prometheus exposition
   internal/config/           # env + .env file configuration
   internal/update/           # signed auto-updater (public key in pubkey.go)
-  internal/service/          # Windows service integration
+  internal/service/          # Windows SCM + Linux systemd (notify/watchdog) integration
   Dockerfile
   .gitea/workflows/ci.yml
   README.md
@@ -261,8 +338,9 @@ are new.
 
 ## Build and CI
 
-- Go 1.23+, `golang.org/x/sys` is the only external dependency (Windows
+- Go 1.23+, two external dependencies: `golang.org/x/sys` (Windows service
-  service integration; not used in the Linux build). `CGO_ENABLED=0`,
+  integration) and `github.com/coreos/go-systemd` (systemd notify/watchdog,
+  Linux build only). `CGO_ENABLED=0`,
   `-ldflags="-s -w"`, version from `git describe` injected via
   `-X main.version=`.
 - Dockerfile: multi-stage, final image `gcr.io/distroless/static` (or

cmd/gpu-turnstile/main.go

@@ -3,11 +3,14 @@
 package main
 
 import (
+	"bufio"
 	"context"
 	"errors"
 	"fmt"
 	"io"
+	"io/fs"
 	"log/slog"
+	"net"
 	"net/http"
 	"os"
 	"os/signal"
@@ -33,14 +36,127 @@ var version = "dev"
 // process: a signed update has been staged and the GPU lock is idle.
 const exitCodeUpdate = 3
 
+// stdoutIsTerminal reports whether stdout is a console (char device), as
+// opposed to a pipe or file — which is what Docker containers and services
+// see.
+func stdoutIsTerminal() bool {
+	fi, err := os.Stdout.Stat()
+	return err == nil && fi.Mode()&os.ModeCharDevice != 0
+}
+
+// parseFlags extracts -config <path> (or -config=<path>), the
+// --install-service / --remove-service switches, --no-copy, -h/--help,
+// -v/--version, --force-update and the hidden --elevated-child marker from
+// args.
+func parseFlags(args []string) (configPath string, install, remove, noCopy, help, showVersion, forceUpdate, elevatedChild bool, rest []string) {
+	rest = args[:0]
+	for i := 0; i < len(args); i++ {
+		switch {
+		case args[i] == "-config" && i+1 < len(args):
+			configPath = args[i+1]
+			i++
+		case strings.HasPrefix(args[i], "-config="):
+			configPath = strings.TrimPrefix(args[i], "-config=")
+		case args[i] == "--install-service" || args[i] == "-install-service":
+			install = true
+		case args[i] == "--remove-service" || args[i] == "-remove-service":
+			remove = true
+		case args[i] == "--no-copy" || args[i] == "-no-copy":
+			noCopy = true
+		case args[i] == "-h" || args[i] == "--help" || args[i] == "-help":
+			help = true
+		case args[i] == "-v" || args[i] == "--version" || args[i] == "-version":
+			showVersion = true
+		case args[i] == "--force-update" || args[i] == "-force-update":
+			forceUpdate = true
+		case args[i] == "--elevated-child":
+			elevatedChild = true
+		default:
+			rest = append(rest, args[i])
+		}
+	}
+	return configPath, install, remove, noCopy, help, showVersion, forceUpdate, elevatedChild, rest
+}
+
+// versionLine is printed at the top of every help and error screen.
+func versionLine() string { return "gpu-turnstile " + version }
+
+const usageText = `GPU arbitration proxy for Ollama + ComfyUI
+
+Usage:
+  gpu-turnstile -config <path>                                run the proxy
+  gpu-turnstile --install-service [--no-copy] [-config path]  install + start as a service
+  gpu-turnstile --remove-service                              stop + uninstall the service
+  gpu-turnstile -v | --version                                print just the version
+  gpu-turnstile --force-update                                check for a signed update now,
+                                                              apply it and restart the service
+  gpu-turnstile -h | --help                                   this help
+
+Options:
+  -config <path>      config file (default: gpu-turnstile.env next to the exe)
+  --install-service   copies the binary into the canonical location
+                      (%ProgramFiles%\gpu-turnstile or /var/lib/gpu-turnstile)
+                      unless --no-copy; on Windows a UAC prompt appears when
+                      the shell is not elevated
+  --no-copy           with --install-service: register the current location as-is
+
+All runtime settings are environment variables or KEY=VALUE lines in the
+config file (OLLAMA_URL, COMFY_URL, LOGLEVEL, ...); see README.md.
+`
+
+// printHelp prints the version header plus the full help text.
+func printHelp() {
+	fmt.Printf("%s — %s", versionLine(), usageText)
+}
+
+// fatalUsage prints the version header, an error message and the one-line
+// usage summary, then exits with code 2.
+func fatalUsage(format string, args ...any) {
+	fmt.Fprintf(os.Stderr, "%s\n\n", versionLine())
+	fmt.Fprintf(os.Stderr, format+"\n\n", args...)
+	fmt.Fprintln(os.Stderr, "usage: gpu-turnstile [-config path] [--install-service [--no-copy] | --remove-service]")
+	fmt.Fprintln(os.Stderr, "       gpu-turnstile service install|remove [-config path]")
+	os.Exit(2)
+}
+
 func main() {
-	configPath, args := splitConfigFlag(os.Args[1:])
+	configPath, install, remove, noCopy, help, showVersion, forceUpdate, elevatedChild, args := parseFlags(os.Args[1:])
+	if showVersion {
+		fmt.Println(version)
+		return
+	}
+	bare := configPath == "" && !install && !remove && !forceUpdate && !elevatedChild && len(args) == 0
+	if help || (bare && stdoutIsTerminal()) {
+		// Bare invocation in a terminal (e.g. double-clicked on Windows)
+		// shows the help instead of starting a proxy window with no visible
+		// explanation. Without a terminal — Docker containers, services,
+		// pipes — a bare invocation starts the proxy as before.
+		printHelp()
+		return
+	}
 	if len(args) > 0 && args[0] == "service" {
-		os.Exit(serviceCommand(configPath, args[1:]))
+		// Legacy subcommand form: gpu-turnstile service install|remove.
+		if len(args) != 2 || (args[1] != "install" && args[1] != "remove") {
+			fatalUsage("error: expected 'service install' or 'service remove'")
+		}
+		install = args[1] == "install"
+		remove = !install
+		args = nil
+	}
+	switch {
+	case install && remove:
+		fatalUsage("error: --install-service and --remove-service are mutually exclusive")
+	case forceUpdate && (install || remove):
+		fatalUsage("error: --force-update cannot be combined with --install-service/--remove-service")
+	case install:
+		os.Exit(serviceCommand(configPath, true, noCopy, elevatedChild))
+	case remove:
+		os.Exit(serviceCommand(configPath, false, noCopy, elevatedChild))
+	case forceUpdate:
+		os.Exit(forceUpdateCommand(configPath, elevatedChild))
 	}
 	if len(args) > 0 {
-		fmt.Fprintf(os.Stderr, "usage: gpu-turnstile [-config path] | gpu-turnstile service install|remove [-config path]\n")
+		fatalUsage("error: unknown arguments: %s", strings.Join(args, " "))
-		os.Exit(2)
 	}
 
 	if exePath, err := os.Executable(); err == nil {
@@ -49,7 +165,7 @@ func main() {
 
 	cfg, err := loadMergedConfig(configPath)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "gpu-turnstile: %v\n", err)
+		fmt.Fprintf(os.Stderr, "%s\n\ngpu-turnstile: %v\n", versionLine(), err)
 		os.Exit(1)
 	}
 	log, logOut, logCloser := newLogger(cfg)
@@ -70,24 +186,6 @@ func main() {
 	}
 }
 
-// splitConfigFlag extracts -config <path> (or -config=<path>) from args.
-func splitConfigFlag(args []string) (string, []string) {
-	var configPath string
-	rest := args[:0]
-	for i := 0; i < len(args); i++ {
-		switch {
-		case args[i] == "-config" && i+1 < len(args):
-			configPath = args[i+1]
-			i++
-		case strings.HasPrefix(args[i], "-config="):
-			configPath = strings.TrimPrefix(args[i], "-config=")
-		default:
-			rest = append(rest, args[i])
-		}
-	}
-	return configPath, rest
-}
-
 // defaultConfigPath returns gpu-turnstile.env next to the executable.
 func defaultConfigPath() string {
 	exe, err := os.Executable()
@@ -157,29 +255,152 @@ func newLogger(cfg config.Config) (*slog.Logger, io.Writer, io.Closer) {
 	return log, out, closer
 }
 
-func serviceCommand(configPath string, args []string) int {
+// waitForEnter keeps an elevated child's console window open until the
-	if len(args) != 1 || (args[0] != "install" && args[0] != "remove") {
+// user has read the output.
-		fmt.Fprintf(os.Stderr, "usage: gpu-turnstile service install|remove [-config path]\n")
+func waitForEnter() {
-		return 2
+	fmt.Print("\nPress Enter to close this window...")
+	bufio.NewReader(os.Stdin).ReadString('\n')
+}
+
+// elevateAndMirror relaunches the current command elevated (UAC) and
+// mirrors the child's exit code. verb is used in messages.
+func elevateAndMirror(verb string) (int, bool) {
+	args := append(append([]string{}, os.Args[1:]...), "--elevated-child")
+	code, err := service.RelaunchElevated(args)
+	if errors.Is(err, service.ErrUserCancelled) {
+		fmt.Fprintln(os.Stderr, "gpu-turnstile: UAC prompt declined")
+		return 1, true
+	}
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "gpu-turnstile: could not elevate: %v\n", err)
+		return 1, true
+	}
+	if code != 0 {
+		fmt.Fprintf(os.Stderr, "gpu-turnstile %s failed in the elevated process (exit %d)\n", verb, code)
+		return code, true
+	}
+	return 0, true
+}
+
+// isPermission reports whether err is a permission problem (Windows
+// ERROR_ACCESS_DENIED, POSIX EACCES/EPERM, possibly wrapped).
+func isPermission(err error) bool {
+	return errors.Is(err, fs.ErrPermission) || strings.Contains(strings.ToLower(err.Error()), "access is denied")
+}
+
+// forceUpdateCommand checks for a signed update immediately, stages it if
+// newer, and restarts the service when it is running so the new binary
+// takes effect. Staging into a system directory and restarting a service
+// need admin rights; instead of prompting unconditionally, permission
+// failures trigger the UAC relaunch so a dev copy in a user-writable
+// directory updates without a prompt.
+func forceUpdateCommand(configPath string, elevatedChild bool) int {
+	if elevatedChild {
+		defer waitForEnter()
+	}
+	cfg, err := loadMergedConfig(configPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n\ngpu-turnstile: %v\n", versionLine(), err)
+		return 1
+	}
+	exePath, err := os.Executable()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "gpu-turnstile: cannot locate executable: %v\n", err)
+		return 1
+	}
+	log, _, logCloser := newLogger(cfg)
+	defer logCloser.Close()
+	u := &update.Updater{Repo: cfg.UpdateRepo, Asset: cfg.UpdateAsset, Version: version, Log: log}
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+	staged, err := u.Check(ctx, exePath)
+	if err != nil && isPermission(err) && !service.Elevated() {
+		code, _ := elevateAndMirror("--force-update")
+		if code == 0 {
+			fmt.Println("update applied (elevated)")
+		}
+		return code
+	}
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "%s\n\ngpu-turnstile: update check failed: %v\n", versionLine(), err)
+		return 1
+	}
+	if !staged {
+		fmt.Printf("%s is up to date\n", versionLine())
+		return 0
+	}
+	fmt.Printf("%s: update staged\n", versionLine())
+	restarted, err := service.RestartIfRunning()
+	if err != nil && isPermission(err) && !service.Elevated() {
+		code, _ := elevateAndMirror("--force-update")
+		if code == 0 {
+			fmt.Println("update applied (elevated)")
+		}
+		return code
+	}
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "gpu-turnstile: update staged but service restart failed: %v\n", err)
+		return 1
+	}
+	if restarted {
+		fmt.Println("service restarted on the new version")
+	} else {
+		fmt.Println("no running service; the new version applies on next start")
+	}
+	return 0
+}
+
+// serviceCommand installs (copyBin = register the canonical-layout copy)
+// or removes the service and reports the result. On Windows, when the
+// shell is not elevated, the command relaunches itself through a UAC
+// prompt and mirrors the elevated child's exit code. An elevated child
+// waits for a keypress so its console window does not flash closed before
+// the output can be read.
+func serviceCommand(configPath string, install, noCopy, elevatedChild bool) int {
+	verb, doneVerb := "remove", "removed"
+	if install {
+		verb, doneVerb = "install", "installed"
+	}
+	if elevatedChild {
+		defer waitForEnter()
+	}
+	if !service.Elevated() {
+		code, done := elevateAndMirror(verb)
+		if done && code != 0 {
+			return code
+		}
+		if done {
+			fmt.Printf("service %s: %s (elevated)\n", service.Name, doneVerb)
+			return 0
+		}
 	}
 	var err error
-	if args[0] == "install" {
+	if install {
 		path := resolveConfigPath(configPath)
 		if abs, absErr := filepath.Abs(path); absErr == nil {
 			path = abs
 		}
-		err = service.Install(path)
+		err = service.Install(path, !noCopy)
 	} else {
 		err = service.Remove()
 	}
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "gpu-turnstile service %s: %v\n", args[0], err)
+		fmt.Fprintf(os.Stderr, "gpu-turnstile service %s: %v\n", verb, err)
 		return 1
 	}
-	fmt.Printf("service %s: %sd\n", service.Name, args[0])
+	fmt.Printf("service %s: %s\n", service.Name, doneVerb)
 	return 0
 }
 
+// orDisabled renders an empty URL as "disabled" for the startup dump.
+func orDisabled(url string) string {
+	if url == "" {
+		return "disabled"
+	}
+	return url
+}
+
 func run(ctx context.Context, cfg config.Config, log *slog.Logger, logOut io.Writer, isService bool) error {
 	// The startup line carries the version and every setting and is emitted
 	// at WARN so it is visible even with the default (quiet) log level.
@@ -187,8 +408,8 @@ func run(ctx context.Context, cfg config.Config, log *slog.Logger, logOut io.Wri
 		"version", version,
 		"listen_ollama", cfg.ListenOllama,
 		"listen_comfy", cfg.ListenComfy,
-		"ollama_url", cfg.OllamaURL,
+		"ollama_url", orDisabled(cfg.OllamaURL),
-		"comfy_url", cfg.ComfyURL,
+		"comfy_url", orDisabled(cfg.ComfyURL),
 		"unload_timeout", cfg.UnloadTimeout,
 		"job_timeout", cfg.JobTimeout,
 		"llm_wait_timeout", cfg.LLMWaitTimeout,
@@ -215,13 +436,20 @@ func run(ctx context.Context, cfg config.Config, log *slog.Logger, logOut io.Wri
 	)
 
 	lk := lock.New(log)
-	ollamaClient, err := ollama.New(cfg.OllamaURL, log)
+	// Each consumer is enabled by setting its URL; a disabled consumer gets
-	if err != nil {
+	// no client, no listener and no probe.
-		return err
+	var ollamaClient *ollama.Client
+	var err error
+	if cfg.OllamaURL != "" {
+		if ollamaClient, err = ollama.New(cfg.OllamaURL, log); err != nil {
+			return err
+		}
 	}
-	comfyClient, err := comfy.New(cfg.ComfyURL, log)
+	var comfyClient *comfy.Client
-	if err != nil {
+	if cfg.ComfyURL != "" {
-		return err
+		if comfyClient, err = comfy.New(cfg.ComfyURL, log); err != nil {
+			return err
+		}
 	}
 
 	srv, err := proxy.New(proxy.Config{
@@ -253,22 +481,54 @@ func run(ctx context.Context, cfg config.Config, log *slog.Logger, logOut io.Wri
 		return err
 	}
 
-	// Probe both upstreams once; failure is logged, not fatal.
+	// Probe the enabled upstreams once; failure is logged, not fatal.
 	probeCtx, probeCancel := context.WithTimeout(ctx, cfg.ProbeTimeout)
-	if err := ollamaClient.Probe(probeCtx); err != nil {
+	if ollamaClient != nil {
-		log.Warn("ollama probe failed", "url", cfg.OllamaURL, "err", err)
+		if err := ollamaClient.Probe(probeCtx); err != nil {
+			log.Warn("ollama probe failed", "url", cfg.OllamaURL, "err", err)
+		}
 	}
-	if err := comfyClient.Probe(probeCtx); err != nil {
+	if comfyClient != nil {
-		log.Warn("comfy probe failed", "url", cfg.ComfyURL, "err", err)
+		if err := comfyClient.Probe(probeCtx); err != nil {
+			log.Warn("comfy probe failed", "url", cfg.ComfyURL, "err", err)
+		}
 	}
 	probeCancel()
 
-	ollamaSrv := &http.Server{Addr: cfg.ListenOllama, Handler: srv.OllamaHandler()}
+	// Bind the listeners up front so a port conflict fails fast and the
-	comfySrv := &http.Server{Addr: cfg.ListenComfy, Handler: srv.ComfyHandler()}
+	// readiness notification below really means "accepting connections".
+	var servers []*http.Server
+	var listeners []net.Listener
+	bind := func(addr string, handler http.Handler, consumer string) error {
+		ln, err := net.Listen("tcp", addr)
+		if err != nil {
+			return fmt.Errorf("listen %s on %s: %w", consumer, addr, err)
+		}
+		servers = append(servers, &http.Server{Addr: addr, Handler: handler})
+		listeners = append(listeners, ln)
+		log.Warn("listening", "consumer", consumer, "addr", addr)
+		return nil
+	}
+	if ollamaClient != nil {
+		if err := bind(cfg.ListenOllama, srv.OllamaHandler(), "ollama"); err != nil {
+			return err
+		}
+	}
+	if comfyClient != nil {
+		if err := bind(cfg.ListenComfy, srv.ComfyHandler(), "comfy"); err != nil {
+			return err
+		}
+	}
 
-	errCh := make(chan error, 2)
+	errCh := make(chan error, len(servers))
-	go func() { errCh <- ollamaSrv.ListenAndServe() }()
+	for i := range servers {
-	go func() { errCh <- comfySrv.ListenAndServe() }()
+		go func(s *http.Server, ln net.Listener) { errCh <- s.Serve(ln) }(servers[i], listeners[i])
+	}
+
+	// Tell systemd we are up and start the watchdog pings; both are no-ops
+	// when not running under a notify/watchdog unit.
+	service.NotifyReady()
+	service.StartWatchdog(ctx)
 
 	if cfg.AutoUpdate {
 		go updateLoop(ctx, cfg, log, lk, isService)
@@ -285,8 +545,9 @@ func run(ctx context.Context, cfg config.Config, log *slog.Logger, logOut io.Wri
 
 	shutdownCtx, shutdownCancel := context.WithTimeout(context.Background(), cfg.ShutdownTimeout)
 	defer shutdownCancel()
-	ollamaSrv.Shutdown(shutdownCtx)
+	for _, s := range servers {
-	comfySrv.Shutdown(shutdownCtx)
+		s.Shutdown(shutdownCtx)
+	}
 	return nil
 }
 

compose.yaml.example

@@ -6,9 +6,11 @@
 # ComfyUI --listen 0.0.0.0 --port 8189).
 services:
   gpu-turnstile:
-    image: git.rambossek.at/public/gpu-turnstile:v0.1.3
+    image: git.rambossek.at/public/gpu-turnstile:v0.1.6
     restart: unless-stopped
     environment:
+      # Each consumer is enabled by setting its URL; leave one unset to
+      # disable that side (no listener, no probe, no lock participation).
       # Services on the Docker host itself:
       OLLAMA_URL: http://host.docker.internal:11435
       COMFY_URL: http://host.docker.internal:8189

go.mod

@@ -3,3 +3,5 @@ module gpu-turnstile
 go 1.23
 
 require golang.org/x/sys v0.29.0
+
+require github.com/coreos/go-systemd/v22 v22.7.0

go.sum

@@ -1,2 +1,4 @@
+github.com/coreos/go-systemd/v22 v22.7.0 h1:LAEzFkke61DFROc7zNLX/WA2i5J8gYqe0rSj9KI28KA=
+github.com/coreos/go-systemd/v22 v22.7.0/go.mod h1:xNUYtjHu2EDXbsxz1i41wouACIwT7Ybq9o0BQhMwD0w=
 golang.org/x/sys v0.29.0 h1:TPYlXGxvx1MGTn2GiZDhnjPA9wZzZeGKHHmKhHYvgaU=
 golang.org/x/sys v0.29.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=

internal/config/config.go

@@ -51,13 +51,12 @@ type Config struct {
 }
 
 // Defaults returns the configuration used when neither the environment nor
-// a config file sets a value.
+// a config file sets a value. The upstream URLs default to empty: a
+// consumer is enabled by setting its URL, disabled by leaving it empty.
 func Defaults() Config {
 	return Config{
 		ListenOllama:   ":11434",
 		ListenComfy:    ":8188",
-		OllamaURL:      "http://127.0.0.1:11435",
-		ComfyURL:       "http://127.0.0.1:8189",
 		UnloadTimeout:  time.Minute,
 		JobTimeout:     15 * time.Minute,
 		LLMWaitTimeout: 10 * time.Minute,
@@ -219,5 +218,8 @@ func Load(getenv func(string) string) (Config, error) {
 	default:
 		return cfg, fmt.Errorf("LOG_FORMAT: must be \"text\" or \"json\"")
 	}
+	if cfg.OllamaURL == "" && cfg.ComfyURL == "" {
+		return cfg, fmt.Errorf("at least one of OLLAMA_URL or COMFY_URL must be set (each URL enables its consumer)")
+	}
 	return cfg, nil
 }

internal/config/config_test.go

@@ -8,13 +8,21 @@ import (
 )
 
 func TestDefaults(t *testing.T) {
-	cfg, err := Load(func(string) string { return "" })
+	cfg, err := Load(func(k string) string {
+		if k == "OLLAMA_URL" {
+			return "http://127.0.0.1:11435"
+		}
+		return ""
+	})
 	if err != nil {
 		t.Fatal(err)
 	}
 	if cfg.ListenOllama != ":11434" || cfg.ListenComfy != ":8188" {
 		t.Fatalf("listen addrs = %s %s", cfg.ListenOllama, cfg.ListenComfy)
 	}
+	if cfg.ComfyURL != "" {
+		t.Fatalf("ComfyURL default = %q, want empty (disabled)", cfg.ComfyURL)
+	}
 	if cfg.UnloadTimeout != time.Minute || cfg.JobTimeout != 15*time.Minute {
 		t.Fatalf("timeouts = %v %v", cfg.UnloadTimeout, cfg.JobTimeout)
 	}
@@ -26,6 +34,13 @@ func TestDefaults(t *testing.T) {
 	}
 }
 
+func TestLoadRequiresConsumer(t *testing.T) {
+	_, err := Load(func(string) string { return "" })
+	if err == nil || !strings.Contains(err.Error(), "OLLAMA_URL") {
+		t.Fatalf("err = %v, want missing-consumer error", err)
+	}
+}
+
 func TestParseEnvFile(t *testing.T) {
 	input := `# comment
 OLLAMA_URL=http://host:11435
@@ -91,6 +106,9 @@ func TestLoadErrors(t *testing.T) {
 			if k == tc.key {
 				return tc.value
 			}
+			if k == "OLLAMA_URL" {
+				return "http://127.0.0.1:11435"
+			}
 			return ""
 		})
 		if err == nil {

internal/proxy/proxy.go

@@ -102,24 +102,37 @@ type Server struct {
 	comfyProxy  *httputil.ReverseProxy
 }
 
-// New builds a Server, validating the upstream URLs.
+// New builds a Server, validating the upstream URLs. At least one of
+// OllamaURL / ComfyURL must be set; an empty URL disables that consumer —
+// its handler is then never served, its client may be nil, and the image
+// job flow skips the Ollama unload/warm steps.
 func New(cfg Config) (*Server, error) {
-	ollamaURL, err := url.Parse(cfg.OllamaURL)
+	if cfg.OllamaURL == "" && cfg.ComfyURL == "" {
-	if err != nil || ollamaURL.Scheme == "" || ollamaURL.Host == "" {
+		return nil, fmt.Errorf("at least one of OllamaURL or ComfyURL is required")
-		return nil, fmt.Errorf("invalid OLLAMA_URL %q", cfg.OllamaURL)
 	}
-	comfyURL, err := url.Parse(cfg.ComfyURL)
+	var ollamaURL, comfyURL *url.URL
-	if err != nil || comfyURL.Scheme == "" || comfyURL.Host == "" {
+	if cfg.OllamaURL != "" {
-		return nil, fmt.Errorf("invalid COMFY_URL %q", cfg.ComfyURL)
+		u, err := url.Parse(cfg.OllamaURL)
+		if err != nil || u.Scheme == "" || u.Host == "" {
+			return nil, fmt.Errorf("invalid OLLAMA_URL %q", cfg.OllamaURL)
+		}
+		ollamaURL = u
+	}
+	if cfg.ComfyURL != "" {
+		u, err := url.Parse(cfg.ComfyURL)
+		if err != nil || u.Scheme == "" || u.Host == "" {
+			return nil, fmt.Errorf("invalid COMFY_URL %q", cfg.ComfyURL)
+		}
+		comfyURL = u
 	}
 	log := cfg.Log
 	if log == nil {
 		log = slog.Default()
 	}
-	if cfg.UnloadPollInterval > 0 {
+	if cfg.UnloadPollInterval > 0 && cfg.Ollama != nil {
 		cfg.Ollama.PollInterval = cfg.UnloadPollInterval
 	}
-	if cfg.HistoryPollInterval > 0 {
+	if cfg.HistoryPollInterval > 0 && cfg.Comfy != nil {
 		cfg.Comfy.PollInterval = cfg.HistoryPollInterval
 	}
 	freeTimeout := cfg.FreeTimeout
@@ -160,7 +173,7 @@ func New(cfg Config) (*Server, error) {
 		max:     backoffMax,
 		log:     log,
 	}
-	return &Server{
+	s := &Server{
 		cfg:            cfg,
 		log:            log,
 		logWriter:      cfg.LogWriter,
@@ -172,9 +185,14 @@ func New(cfg Config) (*Server, error) {
 		busyMode:       busyMode,
 		busyStatus:     busyStatus,
 		busyRetryAfter: busyRetryAfter,
-		ollamaProxy:    newReverseProxy(ollamaURL, retry, log.With("upstream", "ollama")),
+	}
-		comfyProxy:     newReverseProxy(comfyURL, retry, log.With("upstream", "comfy")),
+	if ollamaURL != nil {
-	}, nil
+		s.ollamaProxy = newReverseProxy(ollamaURL, retry, log.With("upstream", "ollama"))
+	}
+	if comfyURL != nil {
+		s.comfyProxy = newReverseProxy(comfyURL, retry, log.With("upstream", "comfy"))
+	}
+	return s, nil
 }
 
 // retryTransport retries requests whose failure means the upstream never
@@ -470,9 +488,13 @@ func (s *Server) OllamaHandler() http.Handler {
 // ComfyHandler serves the ComfyUI-facing listener.
 func (s *Server) ComfyHandler() http.Handler {
 	return s.logRequests("comfy", http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.URL.Path == "/healthz" {
+		switch r.URL.Path {
+		case "/healthz":
 			s.writeHealthz(w)
 			return
+		case "/metrics":
+			s.writeMetrics(w)
+			return
 		}
 		if r.Method == http.MethodPost && r.URL.Path == "/prompt" {
 			s.handlePrompt(w, r)
@@ -527,19 +549,21 @@ func (s *Server) handlePrompt(w http.ResponseWriter, r *http.Request) {
 	s.cfg.Metrics.ObserveLockWait("image", time.Since(start).Seconds())
 	log.Info("image lock acquired")
 
-	uctx, ucancel := context.WithTimeout(r.Context(), s.cfg.UnloadTimeout)
+	if s.cfg.Ollama != nil {
-	elapsed, uerr := s.cfg.Ollama.UnloadAll(uctx)
+		uctx, ucancel := context.WithTimeout(r.Context(), s.cfg.UnloadTimeout)
-	ucancel()
+		elapsed, uerr := s.cfg.Ollama.UnloadAll(uctx)
-	s.cfg.Metrics.ObserveUnload(elapsed.Seconds())
+		ucancel()
-	switch {
+		s.cfg.Metrics.ObserveUnload(elapsed.Seconds())
-	case r.Context().Err() != nil:
+		switch {
-		s.cfg.Lock.ReleaseImage()
+		case r.Context().Err() != nil:
-		return
+			s.cfg.Lock.ReleaseImage()
-	case uerr != nil:
+			return
-		// Degrade, don't fail the user's request on a misbehaving neighbour.
+		case uerr != nil:
-		log.Warn("ollama unload incomplete; continuing", "err", uerr)
+			// Degrade, don't fail the user's request on a misbehaving neighbour.
-	default:
+			log.Warn("ollama unload incomplete; continuing", "err", uerr)
-		log.Info("ollama models unloaded", "seconds", elapsed.Seconds())
+		default:
+			log.Info("ollama models unloaded", "seconds", elapsed.Seconds())
+		}
 	}
 
 	cw := &captureWriter{ResponseWriter: w, status: http.StatusOK, limit: s.captureLimit}
@@ -585,7 +609,7 @@ func (s *Server) finishImageJob(promptID string) {
 	s.cfg.Lock.ReleaseImage()
 	log.Info("image lock released")
 
-	if s.cfg.WarmModel != "" {
+	if s.cfg.Ollama != nil && s.cfg.WarmModel != "" {
 		if state, _, _ := s.cfg.Lock.Snapshot(); state == lock.StateIdle {
 			wctx, wcancel := context.WithTimeout(context.Background(), s.warmTimeout)
 			if err := s.cfg.Ollama.Warm(wctx, s.cfg.WarmModel); err != nil {

internal/proxy/proxy_test.go

@@ -451,3 +451,82 @@ func TestLLMBusyWaitTimeoutRetryAfter(t *testing.T) {
 		t.Fatalf("Retry-After = %q", got)
 	}
 }
+
+func TestComfyOnlyModeSkipsOllama(t *testing.T) {
+	f := newFakes(t)
+
+	comfyClient, err := comfy.New(f.comfy.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	comfyClient.PollInterval = 5 * time.Millisecond
+	srv, err := New(Config{
+		ComfyURL:   f.comfy.URL,
+		Lock:       lock.New(nil),
+		Comfy:      comfyClient,
+		Metrics:    metrics.New(),
+		JobTimeout: 2 * time.Second,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	front := httptest.NewServer(srv.ComfyHandler())
+	defer front.Close()
+
+	resp, err := http.Post(front.URL+"/prompt", "application/json", strings.NewReader(`{}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != 200 {
+		t.Fatalf("prompt status = %d", resp.StatusCode)
+	}
+	f.completeJob()
+	select {
+	case <-f.freeCh:
+	case <-time.After(3 * time.Second):
+		t.Fatal("/free never called")
+	}
+	// With Ollama disabled the unload steps must not happen.
+	if i := f.rec.index("unload"); i >= 0 {
+		f.rec.mu.Lock()
+		t.Fatalf("unload called with ollama disabled; events: %v", f.rec.events)
+	}
+}
+
+func TestOllamaOnlyMode(t *testing.T) {
+	f := newFakes(t)
+
+	ollamaClient, err := ollama.New(f.ollama.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	srv, err := New(Config{
+		OllamaURL:      f.ollama.URL,
+		Lock:           lock.New(nil),
+		Ollama:         ollamaClient,
+		Metrics:        metrics.New(),
+		LLMWaitTimeout: time.Second,
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	front := httptest.NewServer(srv.OllamaHandler())
+	defer front.Close()
+
+	resp, err := http.Post(front.URL+"/api/chat", "application/json", strings.NewReader(`{}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	resp.Body.Close()
+	if resp.StatusCode != 200 {
+		t.Fatalf("chat status = %d", resp.StatusCode)
+	}
+}
+
+func TestNewRequiresConsumer(t *testing.T) {
+	_, err := New(Config{Lock: lock.New(nil), Metrics: metrics.New()})
+	if err == nil {
+		t.Fatal("New with no upstream URLs should fail")
+	}
+}

internal/service/errors.go

@@ -0,0 +1,8 @@
+package service
+
+import "errors"
+
+// ErrUserCancelled is returned by RelaunchElevated when the user declines
+// the UAC prompt. Windows-only in practice; defined here so cross-platform
+// callers can compare against it.
+var ErrUserCancelled = errors.New("UAC prompt declined")

internal/service/notify_linux.go

@@ -0,0 +1,46 @@
+//go:build linux
+
+package service
+
+import (
+	"context"
+	"os"
+	"strconv"
+	"time"
+
+	"github.com/coreos/go-systemd/v22/daemon"
+)
+
+// NotifyReady tells systemd the service is up (Type=notify). It is a no-op
+// when NOTIFY_SOCKET is unset, e.g. in a container or interactive shell.
+func NotifyReady() {
+	daemon.SdNotify(false, daemon.SdNotifyReady)
+}
+
+// NotifyStopping tells systemd the service is shutting down.
+func NotifyStopping() {
+	daemon.SdNotify(false, daemon.SdNotifyStopping)
+}
+
+// StartWatchdog pings the systemd watchdog every half of WATCHDOG_USEC
+// until ctx is cancelled. It is a no-op unless systemd started the process
+// with a watchdog configured (WatchdogSec= in the unit).
+func StartWatchdog(ctx context.Context) {
+	usec, err := strconv.Atoi(os.Getenv("WATCHDOG_USEC"))
+	if err != nil || usec <= 0 {
+		return
+	}
+	interval := time.Duration(usec) * time.Microsecond / 2
+	go func() {
+		ticker := time.NewTicker(interval)
+		defer ticker.Stop()
+		for {
+			select {
+			case <-ctx.Done():
+				return
+			case <-ticker.C:
+				daemon.SdNotify(false, daemon.SdNotifyWatchdog)
+			}
+		}
+	}()
+}

internal/service/notify_other.go

@@ -0,0 +1,14 @@
+//go:build !linux
+
+package service
+
+import "context"
+
+// NotifyReady is a no-op outside Linux (no systemd notify socket).
+func NotifyReady() {}
+
+// NotifyStopping is a no-op outside Linux.
+func NotifyStopping() {}
+
+// StartWatchdog is a no-op outside Linux.
+func StartWatchdog(context.Context) {}

internal/service/service_linux.go

@@ -0,0 +1,201 @@
+//go:build linux
+
+// Package service integrates gpu-turnstile with systemd on Linux: running
+// under a unit with readiness notification and watchdog, plus
+// install/remove helpers that manage a hardened system unit.
+package service
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"os"
+	"os/exec"
+	"os/signal"
+	"path/filepath"
+	"syscall"
+)
+
+// Name matches the Windows service name; the systemd unit is Name + ".service".
+const Name = "gpu-turnstile"
+
+// unitPath is where Install writes the unit file.
+const unitPath = "/etc/systemd/system/" + Name + ".service"
+
+// stateDir holds the installed binary (and staged updates); the unit's
+// StateDirectory= directive makes systemd own it and grant the dynamic
+// user write access. etcConfig is the config file the unit loads.
+const (
+	stateDir  = "/var/lib/" + Name
+	etcConfig = "/etc/" + Name + ".env"
+)
+
+// IsService reports whether the process was started by systemd.
+func IsService() bool { return os.Getenv("INVOCATION_ID") != "" }
+
+// Elevated is always true on Linux: there is no UAC equivalent; privilege
+// errors surface from the failing operation with a "run as root" hint.
+func Elevated() bool { return true }
+
+// RelaunchElevated is a Windows-only concept (UAC).
+func RelaunchElevated([]string) (int, error) {
+	return 0, fmt.Errorf("elevated relaunch is only supported on Windows")
+}
+
+// Run executes run with SIGINT/SIGTERM cancellation (which is how systemctl
+// stop signals the process) and tells systemd when the shutdown begins.
+func Run(run func(ctx context.Context) error) error {
+	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
+	defer stop()
+	defer NotifyStopping()
+	return run(ctx)
+}
+
+// renderUnit builds the hardened systemd unit: Type=notify so systemctl
+// start blocks until the listeners are bound, a 30s watchdog, and
+// restart-on-failure with a 5s delay — which is also what brings up a
+// staged update after the updater exits with a non-zero code.
+//
+// Sandboxing mirrors the Windows virtual account: DynamicUser=yes gives
+// the service a transient per-service UID with no login and no home, the
+// filesystem is read-only except StateDirectory (the install dir, so
+// self-updates can rewrite the binary), and the usual no-privilege-escalation
+// directives apply. The proxy needs nothing but outbound TCP/UDP and the
+// notify socket, so it loses nothing.
+func renderUnit(exePath, configPath string) string {
+	return fmt.Sprintf(`[Unit]
+Description=gpu-turnstile GPU arbitration proxy for Ollama and ComfyUI
+After=network-online.target
+Wants=network-online.target
+
+[Service]
+Type=notify
+WatchdogSec=30s
+ExecStart=%q -config %q
+Restart=on-failure
+RestartSec=5s
+
+DynamicUser=yes
+StateDirectory=%s
+ProtectSystem=strict
+ProtectHome=yes
+PrivateTmp=yes
+NoNewPrivileges=yes
+ProtectKernelTunables=yes
+ProtectKernelModules=yes
+ProtectKernelLogs=yes
+ProtectControlGroups=yes
+ProtectClock=yes
+RestrictNamespaces=yes
+RestrictSUIDSGID=yes
+RestrictRealtime=yes
+LockPersonality=yes
+MemoryDenyWriteExecute=yes
+CapabilityBoundingSet=
+AmbientCapabilities=
+RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
+SystemCallFilter=@system-service
+SystemCallErrorNumber=EPERM
+
+[Install]
+WantedBy=multi-user.target
+`, exePath, configPath, Name)
+}
+
+// copyFile copies src to dst, creating dst with the given mode.
+func copyFile(src, dst string, mode os.FileMode) error {
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+	out, err := os.OpenFile(dst, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, mode)
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+	if _, err := io.Copy(out, in); err != nil {
+		return err
+	}
+	return out.Close()
+}
+
+// Install copies the current executable into /var/lib/gpu-turnstile, makes
+// sure /etc/gpu-turnstile.env exists (copied from the given config file if
+// provided), writes the hardened unit, then enables and starts it. With
+// copyBin=false the current executable location and config path are
+// registered as-is instead. Needs root.
+//
+// The binary lives in the StateDirectory rather than /usr/local/sbin on
+// purpose: replacing a running binary needs write access to its
+// *directory*, and granting the sandboxed service user write access to a
+// shared system directory would let a compromised service overwrite other
+// binaries. /var/lib/gpu-turnstile is exclusively ours.
+func Install(configPath string, copyBin bool) error {
+	exe, err := os.Executable()
+	if err != nil {
+		return err
+	}
+	if abs, absErr := filepath.Abs(exe); absErr == nil {
+		exe = abs
+	}
+	cfg := etcConfig
+	if copyBin {
+		if err := os.MkdirAll(stateDir, 0o755); err != nil {
+			return fmt.Errorf("create %s (run as root): %w", stateDir, err)
+		}
+		installedExe := filepath.Join(stateDir, Name)
+		if exe != installedExe {
+			if err := copyFile(exe, installedExe, 0o755); err != nil {
+				return fmt.Errorf("install binary to %s: %w", installedExe, err)
+			}
+		}
+		exe = installedExe
+		if _, err := os.Stat(etcConfig); os.IsNotExist(err) && configPath != "" {
+			// Missing config is not fatal: the service fails fast with a
+			// clear "no consumer URL" error until the user writes one.
+			copyFile(configPath, etcConfig, 0o644) //nolint:errcheck // best effort
+		}
+	} else if configPath != "" {
+		if abs, absErr := filepath.Abs(configPath); absErr == nil {
+			cfg = abs
+		}
+	}
+	if err := os.WriteFile(unitPath, []byte(renderUnit(exe, cfg)), 0o644); err != nil {
+		return fmt.Errorf("write %s (run as root): %w", unitPath, err)
+	}
+	if out, err := exec.Command("systemctl", "daemon-reload").CombinedOutput(); err != nil {
+		return fmt.Errorf("systemctl daemon-reload: %w (%s)", err, out)
+	}
+	if out, err := exec.Command("systemctl", "enable", "--now", Name+".service").CombinedOutput(); err != nil {
+		return fmt.Errorf("systemctl enable --now: %w (%s)", err, out)
+	}
+	return nil
+}
+
+// Remove stops and disables the service and deletes the unit file and the
+// installed binary. The config file in /etc is left in place (user data).
+func Remove() error {
+	exec.Command("systemctl", "disable", "--now", Name+".service").Run() // ignore: may not exist
+	if err := os.Remove(unitPath); err != nil && !os.IsNotExist(err) {
+		return fmt.Errorf("remove %s: %w", unitPath, err)
+	}
+	os.RemoveAll(stateDir) // installed binary + staged updates; ignore error
+	if out, err := exec.Command("systemctl", "daemon-reload").CombinedOutput(); err != nil {
+		return fmt.Errorf("systemctl daemon-reload: %w (%s)", err, out)
+	}
+	return nil
+}
+
+// RestartIfRunning restarts the systemd unit when it is active (used after
+// a forced update staged a new binary). Reports whether a restart
+// happened. An inactive or missing unit is not an error. Needs root.
+func RestartIfRunning() (bool, error) {
+	if err := exec.Command("systemctl", "is-active", "--quiet", Name+".service").Run(); err != nil {
+		return false, nil // inactive or not installed
+	}
+	if out, err := exec.Command("systemctl", "restart", Name+".service").CombinedOutput(); err != nil {
+		return false, fmt.Errorf("systemctl restart (run as root): %w (%s)", err, out)
+	}
+	return true, nil
+}

internal/service/service_linux_test.go

@@ -0,0 +1,29 @@
+//go:build linux
+
+package service
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestRenderUnit(t *testing.T) {
+	unit := renderUnit("/var/lib/gpu-turnstile/gpu-turnstile", "/etc/gpu-turnstile.env")
+	for _, want := range []string{
+		"Type=notify",
+		"WatchdogSec=30s",
+		`ExecStart="/var/lib/gpu-turnstile/gpu-turnstile" -config "/etc/gpu-turnstile.env"`,
+		"Restart=on-failure",
+		"WantedBy=multi-user.target",
+		"DynamicUser=yes",
+		"StateDirectory=gpu-turnstile",
+		"ProtectSystem=strict",
+		"NoNewPrivileges=yes",
+		"RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6",
+		"SystemCallFilter=@system-service",
+	} {
+		if !strings.Contains(unit, want) {
+			t.Fatalf("unit missing %q:\n%s", want, unit)
+		}
+	}
+}

internal/service/service_other.go

@@ -1,8 +1,8 @@
-//go:build !windows
+//go:build !windows && !linux
 
-// Package service provides the non-Windows stubs for the Windows service
+// Package service provides the stubs for platforms without service
-// integration. Run falls back to plain signal handling; install/remove
+// integration (Windows uses the SCM, Linux uses systemd). Run falls back
-// are unsupported.
+// to plain signal handling; install/remove are unsupported.
 package service
 
 import (
@@ -15,7 +15,7 @@ import (
 // Name matches the Windows service name.
 const Name = "gpu-turnstile"
 
-var errUnsupported = errors.New("service management is only supported on Windows")
+var errUnsupported = errors.New("service management is only supported on Windows and Linux (systemd)")
 
 // IsService is always false on non-Windows platforms.
 func IsService() bool { return false }
@@ -28,8 +28,18 @@ func Run(run func(ctx context.Context) error) error {
 	return run(ctx)
 }
 
-// Install is unsupported on non-Windows platforms.
+// Install is unsupported on non-Windows, non-Linux platforms.
-func Install(string) error { return errUnsupported }
+func Install(string, bool) error { return errUnsupported }
 
-// Remove is unsupported on non-Windows platforms.
+// Remove is unsupported on non-Windows, non-Linux platforms.
 func Remove() error { return errUnsupported }
+
+// Elevated is always true here: there is no UAC concept, and privilege
+// errors surface from the failing operation with a "run as root" hint.
+func Elevated() bool { return true }
+
+// RelaunchElevated is unsupported on non-Windows, non-Linux platforms.
+func RelaunchElevated([]string) (int, error) { return 0, errUnsupported }
+
+// RestartIfRunning is a no-op on platforms without service integration.
+func RestartIfRunning() (bool, error) { return false, nil }

internal/service/service_windows.go

@@ -2,22 +2,53 @@
 
 // Package service integrates gpu-turnstile with the Windows Service
 // Control Manager: running as a service with graceful stop, plus
-// install/remove helpers.
+// install/remove helpers. Installed services always run as the virtual
+// account NT SERVICE\gpu-turnstile — a per-service low-privilege identity
+// managed by the SCM, with no password and no admin rights.
 package service
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"io"
 	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"syscall"
 	"time"
+	"unsafe"
 
+	"golang.org/x/sys/windows"
 	"golang.org/x/sys/windows/svc"
 	"golang.org/x/sys/windows/svc/mgr"
+
+	"gpu-turnstile/internal/config"
 )
 
 // Name is the Windows service name.
 const Name = "gpu-turnstile"
 
+// virtualAccount is the per-service identity the service runs as. The SCM
+// manages it: no password, automatic "log on as a service" right, gone
+// when the service is removed.
+const virtualAccount = `NT SERVICE\` + Name
+
+// installDirs returns the canonical install (Program Files) and data
+// (ProgramData) directories.
+func installDirs() (install, data string) {
+	pf := os.Getenv("ProgramFiles")
+	if pf == "" {
+		pf = `C:\Program Files`
+	}
+	pd := os.Getenv("ProgramData")
+	if pd == "" {
+		pd = `C:\ProgramData`
+	}
+	return filepath.Join(pf, Name), filepath.Join(pd, Name)
+}
+
 // IsService reports whether the process is running as a Windows service.
 func IsService() bool {
 	isSvc, err := svc.IsWindowsService()
@@ -64,15 +95,53 @@ func (h *handler) Execute(_ []string, requests <-chan svc.ChangeRequest, status
 	}
 }
 
-// Install registers gpu-turnstile as an auto-start Windows service whose
+// Install registers gpu-turnstile as an auto-start Windows service running
-// binPath loads the given config file. Recovery actions restart the
+// as the NT SERVICE\gpu-turnstile virtual account, whose binPath loads the
-// service after 5s on failure — this is also what brings up a staged
+// given config file. With copyBin it first creates the canonical layout —
-// update after the updater exits with a non-zero code.
+// the binary is copied into %ProgramFiles%\gpu-turnstile and the config
-func Install(configPath string) error {
+// next to it (an existing config there is kept), %ProgramData%\gpu-turnstile
+// is created for logs — and registers that copy; with copyBin=false the
+// current executable location is registered as-is. Recovery actions restart
+// the service after 5s on failure — this is also what brings up a staged
+// update after the updater exits with a non-zero code. After registering,
+// the virtual account is granted modify access to the install and data
+// directories (self-updates rewrite the exe), and read access to the
+// config file if it lives elsewhere. The grants must come after
+// CreateService: the virtual account's SID only exists once the service is
+// registered.
+func Install(configPath string, copyBin bool) error {
 	exe, err := os.Executable()
 	if err != nil {
 		return err
 	}
+	if abs, absErr := filepath.Abs(exe); absErr == nil {
+		exe = abs
+	}
+	if configPath != "" {
+		if abs, absErr := filepath.Abs(configPath); absErr == nil {
+			configPath = abs
+		}
+	}
+
+	installDir, _ := installDirs()
+	if copyBin && !strings.EqualFold(filepath.Dir(exe), installDir) {
+		if err := os.MkdirAll(installDir, 0o755); err != nil {
+			return fmt.Errorf("create %s: %w", installDir, err)
+		}
+		installedExe := filepath.Join(installDir, "gpu-turnstile.exe")
+		if err := copyFile(exe, installedExe); err != nil {
+			return fmt.Errorf("copy binary to %s: %w", installedExe, err)
+		}
+		exe = installedExe
+		targetCfg := filepath.Join(installDir, "gpu-turnstile.env")
+		if configPath != "" && !strings.EqualFold(configPath, targetCfg) {
+			if _, statErr := os.Stat(targetCfg); os.IsNotExist(statErr) {
+				copyFile(configPath, targetCfg) //nolint:errcheck // best effort
+			}
+			configPath = targetCfg
+		}
+	}
+
 	m, err := mgr.Connect()
 	if err != nil {
 		return fmt.Errorf("connect to service manager (run as administrator): %w", err)
@@ -81,9 +150,10 @@ func Install(configPath string) error {
 
 	binPath := fmt.Sprintf(`"%s" -config "%s"`, exe, configPath)
 	s, err := m.CreateService(Name, binPath, mgr.Config{
-		StartType:   mgr.StartAutomatic,
+		StartType:        mgr.StartAutomatic,
-		DisplayName: "gpu-turnstile",
+		DisplayName:      "gpu-turnstile",
-		Description: "GPU arbitration proxy for Ollama and ComfyUI",
+		Description:      "GPU arbitration proxy for Ollama and ComfyUI",
+		ServiceStartName: virtualAccount,
 	})
 	if err != nil {
 		return fmt.Errorf("create service: %w", err)
@@ -97,10 +167,71 @@ func Install(configPath string) error {
 	if err := s.SetRecoveryActionsOnNonCrashFailures(true); err != nil {
 		return fmt.Errorf("set failure actions flag: %w", err)
 	}
+
+	if err := grantAll(exe, configPath); err != nil {
+		s.Delete() // roll back so a retry starts clean
+		return err
+	}
+	// Best effort: start now instead of waiting for the next boot. A
+	// missing config (no consumer URLs) fails the start; the service stays
+	// registered and can be started once the config exists.
+	s.Start()
 	return nil
 }
 
-// Remove stops (if running) and unregisters the service.
+// copyFile copies src to dst (0755 on the new file).
+func copyFile(src, dst string) error {
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+	out, err := os.OpenFile(dst, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0o755)
+	if err != nil {
+		return err
+	}
+	if _, err := io.Copy(out, in); err != nil {
+		out.Close()
+		return err
+	}
+	return out.Close()
+}
+
+// grantAll gives the virtual account every ACL the service needs: modify
+// on the install and ProgramData directories and the LOG_FILE directory
+// (if configured elsewhere), read on a config file outside the install
+// directory.
+func grantAll(exe, configPath string) error {
+	_, dataDir := installDirs()
+	if err := os.MkdirAll(dataDir, 0o755); err != nil {
+		return fmt.Errorf("create %s: %w", dataDir, err)
+	}
+	if err := grantAccess(dataDir, "(OI)(CI)(M)"); err != nil {
+		return err
+	}
+	exeDir := filepath.Dir(exe)
+	if err := grantAccess(exeDir, "(OI)(CI)(M)"); err != nil {
+		return err
+	}
+	if configPath != "" && !strings.HasPrefix(strings.ToLower(configPath), strings.ToLower(exeDir)+`\`) {
+		if err := grantAccess(configPath, "(R)"); err != nil {
+			return err
+		}
+	}
+	if logFile := configuredLogFile(configPath); logFile != "" {
+		dir := filepath.Dir(logFile)
+		if err := os.MkdirAll(dir, 0o755); err == nil {
+			if err := grantAccess(dir, "(OI)(CI)(M)"); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+// Remove stops (if running) and unregisters the service. The virtual
+// account ceases to exist with it; the ACL grants on the install and log
+// directories are left in place (harmless without the account).
 func Remove() error {
 	m, err := mgr.Connect()
 	if err != nil {
@@ -118,3 +249,150 @@ func Remove() error {
 	}
 	return nil
 }
+
+var procShellExecuteExW = windows.NewLazySystemDLL("shell32.dll").NewProc("ShellExecuteExW")
+
+const seeMaskNoCloseProcess = 0x40
+
+// shellExecuteInfo mirrors SHELLEXECUTEINFOW (64-bit layout).
+type shellExecuteInfo struct {
+	cbSize       uint32
+	fMask        uint32
+	hwnd         uintptr
+	lpVerb       *uint16
+	lpFile       *uint16
+	lpParameters *uint16
+	lpDirectory  *uint16
+	nShow        int32
+	_            int32
+	hInstApp     uintptr
+	lpIDList     unsafe.Pointer
+	lpClass      *uint16
+	hkeyClass    uintptr
+	dwHotKey     uint32
+	_            uint32
+	hIcon        uintptr
+	hProcess     windows.Handle
+}
+
+// Elevated reports whether the current process token is UAC-elevated.
+func Elevated() bool {
+	var token windows.Token
+	if err := windows.OpenProcessToken(windows.CurrentProcess(), windows.TOKEN_QUERY, &token); err != nil {
+		return false
+	}
+	defer token.Close()
+	return token.IsElevated()
+}
+
+// RelaunchElevated re-runs the current executable elevated via the UAC
+// "runas" verb with the given arguments, waits for the child, and returns
+// its exit code. The child gets a fresh console window for its output.
+func RelaunchElevated(args []string) (int, error) {
+	exe, err := os.Executable()
+	if err != nil {
+		return 0, err
+	}
+	quoted := make([]string, len(args))
+	for i, a := range args {
+		quoted[i] = syscall.EscapeArg(a)
+	}
+	cwd, _ := os.Getwd()
+	verb, _ := windows.UTF16PtrFromString("runas")
+	exeP, _ := windows.UTF16PtrFromString(exe)
+	params, _ := windows.UTF16PtrFromString(strings.Join(quoted, " "))
+	dir, _ := windows.UTF16PtrFromString(cwd)
+	info := shellExecuteInfo{
+		fMask:        seeMaskNoCloseProcess,
+		lpVerb:       verb,
+		lpFile:       exeP,
+		lpParameters: params,
+		lpDirectory:  dir,
+		nShow:        windows.SW_NORMAL,
+	}
+	info.cbSize = uint32(unsafe.Sizeof(info))
+	r, _, callErr := procShellExecuteExW.Call(uintptr(unsafe.Pointer(&info)))
+	if r == 0 {
+		if errors.Is(callErr, syscall.Errno(1223)) { // ERROR_CANCELLED
+			return 0, ErrUserCancelled
+		}
+		return 0, fmt.Errorf("ShellExecuteEx: %w", callErr)
+	}
+	defer windows.CloseHandle(windows.Handle(info.hProcess))
+	windows.WaitForSingleObject(windows.Handle(info.hProcess), windows.INFINITE)
+	var code uint32
+	if err := windows.GetExitCodeProcess(windows.Handle(info.hProcess), &code); err != nil {
+		return 0, err
+	}
+	return int(code), nil
+}
+
+// grantAccess gives the virtual account the icacls permission set (e.g.
+// "(OI)(CI)(M)") on path.
+func grantAccess(path, perms string) error {
+	out, err := exec.Command("icacls", path, "/grant", virtualAccount+":"+perms).CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("grant %s access to %s: %w (%s)", virtualAccount, path, err, strings.TrimSpace(string(out)))
+	}
+	return nil
+}
+
+// configuredLogFile reads LOG_FILE from the config file so the installer
+// can pre-create and ACL the log directory. "" when unset or unreadable.
+func configuredLogFile(configPath string) string {
+	f, err := os.Open(configPath)
+	if err != nil {
+		return ""
+	}
+	defer f.Close()
+	values, err := config.ParseEnvFile(f)
+	if err != nil {
+		return ""
+	}
+	return values["LOG_FILE"]
+}
+
+// RestartIfRunning restarts the service when it is installed and running
+// (used after a forced update staged a new binary). Reports whether a
+// restart happened. A service that is not installed or not running is not
+// an error. Needs elevation.
+func RestartIfRunning() (bool, error) {
+	m, err := mgr.Connect()
+	if err != nil {
+		return false, fmt.Errorf("connect to service manager (run as administrator): %w", err)
+	}
+	defer m.Disconnect()
+	s, err := m.OpenService(Name)
+	if err != nil {
+		return false, nil // not installed
+	}
+	defer s.Close()
+	st, err := s.Query()
+	if err != nil {
+		return false, fmt.Errorf("query service: %w", err)
+	}
+	if st.State != svc.Running && st.State != svc.StartPending {
+		return false, nil
+	}
+	if _, err := s.Control(svc.Stop); err != nil {
+		return false, fmt.Errorf("stop service: %w", err)
+	}
+	deadline := time.Now().Add(30 * time.Second)
+	for {
+		st, err = s.Query()
+		if err != nil {
+			return false, fmt.Errorf("query service: %w", err)
+		}
+		if st.State == svc.Stopped {
+			break
+		}
+		if time.Now().After(deadline) {
+			return false, fmt.Errorf("service did not stop within 30s")
+		}
+		time.Sleep(300 * time.Millisecond)
+	}
+	if err := s.Start(); err != nil {
+		return false, fmt.Errorf("start service: %w", err)
+	}
+	return true, nil
+}

internal/update/pubkey.go

@@ -11,6 +11,6 @@ package update
 // the RELEASE_SIGNING_KEY repository secret. When empty, the updater refuses
 // to update (e.g. development builds).
 var publicKeyPEM = `-----BEGIN PUBLIC KEY-----
-MCowBQYDK2VwAyEA+gJbSvgeYX58woPQGbSC8x8Zw4OTDiiQ7/19seZKfSQ=
+MCowBQYDK2VwAyEAqTAJ0CCeAQI7MhFlgc5xNmF/CfvLVUAY3ZAoeAS0tT8=
 -----END PUBLIC KEY-----
 `