diff --git a/daemon.go b/daemon.go
index 778abbb..6571d47 100644
--- a/daemon.go
+++ b/daemon.go
@@ -125,20 +125,20 @@ func attachContext(dctx *Context) (isChild bool) {
 
 // Background Converts the current process to a background process
 // If `WithNoExit()` is called, it doesn't exit
-func Background(ctx context.Context, dctx *Context, opts ...Option) (*exec.Cmd, error) {
+func Background(ctx context.Context, dctx *Context, opts ...Option) (isParent bool, cmd *exec.Cmd, err error) {
 	for _, o := range opts {
 		o.apply(defaultOption)
 	}
 
 	if attachContext(dctx) {
-		return nil, nil
+		return
 	}
 
 	// starting child process
-	cmd, err := startProc(ctx, dctx)
+	cmd, err = startProc(ctx, dctx)
 	if err != nil {
 		dctx.log("[start exec process failed, err: %s]\n", dctx.Pid, err)
-		return nil, err
+		return
 	} else {
 		dctx.CPid = cmd.Process.Pid
 		if !defaultOption.exit {
@@ -148,13 +148,13 @@ func Background(ctx context.Context, dctx *Context, opts ...Option) (*exec.Cmd,
 	}
 
 	if defaultOption.exit {
-		os.Exit(0)
+		isParent = true
 	}
 
-	return cmd, nil
+	return
 }
 
-// startProc start an process
+// startProc start am process
 func startProc(ctx context.Context, dctx *Context) (*exec.Cmd, error) {
 	// console show process information just use Args[0]
 	// so we should wrapper the args for show process full command
@@ -166,8 +166,8 @@ func startProc(ctx context.Context, dctx *Context) (*exec.Cmd, error) {
 		}
 	}
 	cmd := &exec.Cmd{
-		Path: execs[0],
-		Args: append([]string{strings.Join(args, " ")}, dctx.Args[1:]...),
+		Path:        execs[0],
+		Args:        append([]string{strings.Join(args, " ")}, dctx.Args[1:]...),
 		Env:         dctx.Env,
 		SysProcAttr: &dctx.ProcAttr,
 	}
@@ -200,12 +200,22 @@ func startProc(ctx context.Context, dctx *Context) (*exec.Cmd, error) {
 }
 
 // Run An supervisor daemon
-func (dctx *Context) Run(ctx context.Context) error {
-	_, err := Background(ctx, dctx)
+func (dctx *Context) Run(ctx context.Context) (isParent bool, err error) {
+	if running, pid := dctx.ProcessRunning(); running {
+		err = processAlreadyExists{Pid: pid}
+
+		return
+	}
+
+	isParent, _, err = Background(ctx, dctx)
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	if isParent {
+		return
+	}
+
 	dctx.Count = 1
 	isReset := false
 	dctx.ErrNum = 0
@@ -251,7 +261,7 @@ func (dctx *Context) Run(ctx context.Context) error {
 		dctx.ExtraFiles = extraFile
 
 		begin := time.Now()
-		cmd, err := Background(ctx, dctx, WithNoExit())
+		_, cmd, err := Background(ctx, dctx, WithNoExit())
 		if err != nil {
 			dctx.log("[supervisor(%d)] [child process start failed, err: %s]\n", dctx.Pid, err)
 			dctx.ErrNum++
@@ -399,7 +409,7 @@ func (dctx *Context) Run(ctx context.Context) error {
 		}
 	}
 
-	return nil
+	return
 }
 
 func (dctx *Context) cleanNamedPipeEtc() *Context {
@@ -442,6 +452,7 @@ func (dctx *Context) cleanAll() {
 
 // output log-message to Context.Logger
 func (dctx *Context) log(format string, args ...interface{}) {
+	format = fmt.Sprintf("[%s] %s", time.Now().String(), format)
 	_, fe := fmt.Fprintf(dctx.Logger, format, args...)
 	if fe != nil {
 		log.Fatal(fe)
@@ -450,6 +461,7 @@ func (dctx *Context) log(format string, args ...interface{}) {
 
 // output log-message to Context.PanicLogger
 func (dctx *Context) logPanic(format string, args ...interface{}) {
+	format = fmt.Sprintf("[%s] %s", time.Now().String(), format)
 	_, fe := fmt.Fprintf(dctx.PanicLogger, format, args...)
 	if fe != nil {
 		log.Fatal(fe)
@@ -519,29 +531,62 @@ func (dctx *Context) syncCPidIntoFile() (err error) {
 	return
 }
 
+func (dctx *Context) ProcessRunning() (running bool, pid int) {
+	if id, _ := strconv.Atoi(os.Getenv(EnvName)); id > 0 {
+		return
+	}
+
+	_, running, pid = ExistByPidFile(dctx.CPidFile)
+
+	return
+}
+
 // ExistByPidFile exists by pid file read pid
-func ExistByPidFile(pidFile string) (err error, exist bool) {
-	file, err := os.OpenFile(pidFile, os.O_RDONLY, 0644)
+func ExistByPidFile(pidFile string) (err error, exist bool, pid int) {
+	var file *os.File
+
+	file, err = os.OpenFile(pidFile, os.O_RDONLY, 0644)
 	defer file.Close()
 	if err != nil {
-		return err, false
+		return
 	}
-	pidStr, err := ioutil.ReadAll(file)
+
+	var pidStr []byte
+	pidStr, err = ioutil.ReadAll(file)
 	if err != nil {
-		return err, false
+		return
 	}
-	pid, err := strconv.Atoi(string(pidStr))
+
+	pid, err = strconv.Atoi(string(pidStr))
 	if err != nil {
-		return err, false
+		return
 	}
-	p, err := os.FindProcess(pid)
+
+	var p *os.Process
+	p, err = os.FindProcess(pid)
 	if err != nil {
-		return err, false
+		return
 	}
+
 	err = p.Signal(syscall.Signal(0))
 	if err != nil {
-		return err, false
+		return
 	} else {
-		return nil, true
+		exist = true
+
+		return
 	}
 }
+
+type processAlreadyExists struct {
+	Pid int
+}
+
+func (p processAlreadyExists) Error() string {
+	return fmt.Sprintf("a running process already exists on pid=%d", p.Pid)
+}
+
+func (p processAlreadyExists) String() string {
+	return p.Error()
+}
+
diff --git a/example/backgroud.go b/example/backgroud.go
index 4e55fa6..cdaee5f 100644
--- a/example/backgroud.go
+++ b/example/backgroud.go
@@ -13,15 +13,17 @@ func main() {
 	logName := "daemon.log"
 	stdout, err := os.OpenFile(logName, os.O_WRONLY|os.O_APPEND|os.O_CREATE, 0666)
 
-	_, err = daemon.Background(context.Background(), &daemon.Context{
+	isParent, _, err := daemon.Background(context.Background(), &daemon.Context{
 		ProcAttr: syscall.SysProcAttr{},
 		//Logger:   os.Stdout,
 		Logger: stdout,
 	})
+
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	log.Println("isParent: ", isParent)
 	log.Println(os.Getpid(), "start...")
 	time.Sleep(time.Second * 10)
 	log.Println(os.Getpid(), "end")
diff --git a/example/daemon.go b/example/daemon.go
index d909357..09c99e3 100644
--- a/example/daemon.go
+++ b/example/daemon.go
@@ -19,8 +19,6 @@ func main() {
 	ctx := context.Background()
 	dctx := daemon.Context{
 		//Chroot:   "./pipe",
-		//PidFile: "./daemon.pid",
-		//CPidFile: "./main.pid",
 		ProcAttr: syscall.SysProcAttr{},
 		//Logger:   os.Stdout,
 		Logger:   stdout,
@@ -30,11 +28,15 @@ func main() {
 		},
 	}
 
-	err = dctx.Run(ctx)
+	parent, err := dctx.Run(ctx)
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	if parent {
+		return
+	}
+
 	// belong func main()
 	log.Println(os.Getpid(), "start...")
 	time.Sleep(time.Second * 10)
diff --git a/example/daemon_recover.go b/example/daemon_recover.go
index f1bbc51..9196844 100644
--- a/example/daemon_recover.go
+++ b/example/daemon_recover.go
@@ -30,11 +30,15 @@ func main() {
 		},
 	}
 
-	err = dctx.Run(ctx)
+	parent, err := dctx.Run(ctx)
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	if parent {
+		return
+	}
+
 	// belong func main()
 	dctx.WithRecovery(func() {
 		log.Println(os.Getpid(), "start...")
diff --git a/example/daemon_signal.go b/example/daemon_signal.go
index 26d9857..a488fbf 100644
--- a/example/daemon_signal.go
+++ b/example/daemon_signal.go
@@ -27,11 +27,15 @@ func main() {
 		},
 	}
 
-	err = dctx.Run(ctx)
+	parent, err := dctx.Run(ctx)
 	if err != nil {
 		log.Fatal(err)
 	}
 
+	if parent {
+		return
+	}
+
 	// belong func main()
 	dctx.WithRecovery(func() {
 		wg := new(sync.WaitGroup)