TUN-5933: Better messaging to help user when installing service if it is already installed

cmd/cloudflared/service_template.go

@@ -44,7 +44,7 @@ func (st *ServiceTemplate) Generate(args *ServiceTemplateArgs) error {
 		return err
 	}
 	if _, err = os.Stat(resolvedPath); err == nil {
-		return fmt.Errorf("cloudflared service is already installed at %s", resolvedPath)
+		return fmt.Errorf(serviceAlreadyExistsWarn(resolvedPath))
 	}
 
 	var buffer bytes.Buffer
@@ -75,6 +75,15 @@ func (st *ServiceTemplate) Remove() error {
 	return nil
 }
 
+func serviceAlreadyExistsWarn(service string) string {
+	return fmt.Sprintf("cloudflared service is already installed at %s; if you are running a cloudflared tunnel, you "+
+		"can point it to multiple origins, avoiding the need to run more than one cloudflared service in the "+
+		"same machine; otherwise if you are really sure, you can do `cloudflared service uninstall` to clean "+
+		"up the existing service and then try again this command",
+		service,
+	)
+}
+
 func runCommand(command string, args ...string) error {
 	cmd := exec.Command(command, args...)
 	stderr, err := cmd.StderrPipe()

cmd/cloudflared/windows_service.go

@@ -191,7 +191,7 @@ func installWindowsService(c *cli.Context) error {
 	log := zeroLogger.With().Str(LogFieldWindowsServiceName, windowsServiceName).Logger()
 	if err == nil {
 		s.Close()
-		return fmt.Errorf("Service %s already exists", windowsServiceName)
+		return fmt.Errorf(serviceAlreadyExistsWarn(windowsServiceName))
 	}
 	extraArgs, err := getServiceExtraArgsFromCliArgs(c, &log)
 	if err != nil {