Install writes a fully commented sample env file when no config exists

internal/service/service_linux.go

@@ -15,6 +15,8 @@ import (
 	"os/signal"
 	"path/filepath"
 	"syscall"
+
+	"gpu-turnstile/internal/config"
 )
 
 // Name matches the Windows service name; the systemd unit is Name + ".service".
@@ -170,10 +172,17 @@ func Install(configPath string, copyBin bool) error {
 			}
 		}
 		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
+		if _, err := os.Stat(etcConfig); os.IsNotExist(err) {
+			if configPath != "" {
+				copyFile(configPath, etcConfig, 0o644) //nolint:errcheck // best effort
+			} else {
+				// No config at all: install a fully commented sample
+				// covering every setting. LOG_FILE stays commented —
+				// stderr goes to the journal on Linux.
+				if err := os.WriteFile(etcConfig, []byte(config.SampleEnv("")), 0o644); err != nil {
+					return fmt.Errorf("write %s: %w", etcConfig, err)
+				}
+			}
 		}
 	} else if configPath != "" {
 		if abs, absErr := filepath.Abs(configPath); absErr == nil {

internal/service/service_windows.go

@@ -172,10 +172,16 @@ func Install(configPath string, copyBin bool) error {
 				}
 			}
 		}
-		// A service has no console: without LOG_FILE the output vanishes, so
-		// the installed env file defaults to logging into ProgramData. An
-		// existing LOG_FILE setting is left alone.
-		if err := ensureLogFile(targetCfg, filepath.Join(dataDir, "gpu-turnstile.log")); err != nil {
+		// A service has no console: without LOG_FILE the output vanishes.
+		// With no config at all, install a fully commented sample covering
+		// every setting (only LOG_FILE active); an existing config just gets
+		// a LOG_FILE line appended if it has none.
+		logPath := filepath.Join(dataDir, "gpu-turnstile.log")
+		if _, statErr := os.Stat(targetCfg); os.IsNotExist(statErr) {
+			if err := os.WriteFile(targetCfg, []byte(config.SampleEnv(logPath)), 0o644); err != nil {
+				return fmt.Errorf("write %s: %w", targetCfg, err)
+			}
+		} else if err := ensureLogFile(targetCfg, logPath); err != nil {
 			return err
 		}
 		configPath = targetCfg