diff --git a/cmd/shadowsocks-local/local.go b/cmd/shadowsocks-local/local.go
index 7bfbd5e..81481f6 100644
--- a/cmd/shadowsocks-local/local.go
+++ b/cmd/shadowsocks-local/local.go
@@ -178,7 +178,7 @@ func run(port, password, server string) {
 		log.Fatal(err)
 	}
 	encTbl := ss.GetTable(password)
-	log.Printf("starting server at port %v ...\n", port)
+	log.Printf("starting local socks5 server at port %v, remote shadowsocks server %s...\n", port, server)
 	for {
 		conn, err := ln.Accept()
 		if err != nil {
@@ -191,14 +191,24 @@ func run(port, password, server string) {
 
 func main() {
 	var configFile string
+	var cmdConfig ss.Config
+
 	flag.StringVar(&configFile, "c", "config.json", "specify config file")
+	flag.StringVar(&cmdConfig.Server, "s", "", "server address")
+	flag.StringVar(&cmdConfig.Password, "k", "", "password")
+	flag.IntVar(&cmdConfig.ServerPort, "p", 0, "server port")
+	flag.IntVar(&cmdConfig.LocalPort, "l", 0, "local socks5 proxy port")
+	flag.BoolVar((*bool)(&debug), "d", false, "print debug message")
+
 	flag.Parse()
 
 	config, err := ss.ParseConfig(configFile)
 	if err != nil {
 		return
 	}
-	debug = ss.Debug
+	ss.UpdateConfig(config, &cmdConfig)
+	ss.SetDebug(debug)
+
 	run(strconv.Itoa(config.LocalPort), config.Password,
 		config.Server+":"+strconv.Itoa(config.ServerPort))
 }
diff --git a/cmd/shadowsocks-server/server.go b/cmd/shadowsocks-server/server.go
index c1f56f2..8f7b321 100644
--- a/cmd/shadowsocks-server/server.go
+++ b/cmd/shadowsocks-server/server.go
@@ -152,14 +152,23 @@ func run(port, password string) {
 
 func main() {
 	var configFile string
+	var cmdConfig ss.Config
+
 	flag.StringVar(&configFile, "c", "config.json", "specify config file")
+	flag.StringVar(&cmdConfig.Password, "k", "", "password")
+	flag.IntVar(&cmdConfig.ServerPort, "p", 0, "server port")
+	flag.IntVar(&cmdConfig.Timeout, "t", 60, "connection timeout (in seconds)")
+	flag.BoolVar((*bool)(&debug), "d", false, "print debug message")
+
 	flag.Parse()
 
 	config, err := ss.ParseConfig(configFile)
 	if err != nil {
 		return
 	}
-	debug = ss.Debug
+	ss.UpdateConfig(config, &cmdConfig)
+	ss.SetDebug(debug)
+
 	if len(config.PortPassword) == 0 {
 		run(strconv.Itoa(config.ServerPort), config.Password)
 	} else {
diff --git a/config.json b/config.json
index 02a39cc..0685796 100644
--- a/config.json
+++ b/config.json
@@ -7,6 +7,5 @@
         "8388": "barfoo!",
         "8387": "foobar!"
     },
-    "timeout":60,
-    "debug":true
+    "timeout":60
 }
diff --git a/shadowsocks/config.go b/shadowsocks/config.go
index b8a45ba..91086c1 100644
--- a/shadowsocks/config.go
+++ b/shadowsocks/config.go
@@ -12,6 +12,7 @@ import (
 	"io/ioutil"
 	"log"
 	"os"
+	"reflect"
 	"time"
 )
 
@@ -22,7 +23,6 @@ type Config struct {
 	Password     string            `json:"password"`
 	PortPassword map[string]string `json:"port_password"`
 	Timeout      int               `json:"timeout"`
-	Debug        bool              `json:"debug"`
 }
 
 var readTimeout time.Duration
@@ -46,7 +46,40 @@ func ParseConfig(path string) (config *Config, err error) {
 		log.Println("can not parse config:", err)
 		return nil, err
 	}
-	Debug = DebugLog(config.Debug)
 	readTimeout = time.Duration(config.Timeout) * time.Second
 	return
 }
+
+func SetDebug(d DebugLog) {
+	Debug = d
+}
+
+// Useful for command line to override options specified in config file
+// Debug is not updated.
+func UpdateConfig(old, new *Config) {
+	// Using reflection here is not necessary, but it's a good exercise.
+	// For more information on reflections in Go, read "The Laws of Reflection"
+	// http://golang.org/doc/articles/laws_of_reflection.html
+	newVal := reflect.ValueOf(new).Elem()
+	oldVal := reflect.ValueOf(old).Elem()
+
+	// typeOfT := newVal.Type()
+	for i := 0; i < newVal.NumField(); i++ {
+		newField := newVal.Field(i)
+		oldField := oldVal.Field(i)
+		// log.Printf("%d: %s %s = %v\n", i,
+		// typeOfT.Field(i).Name, newField.Type(), newField.Interface())
+		switch newField.Kind() {
+		case reflect.String:
+			s := newField.String()
+			if s != "" {
+				oldField.SetString(s)
+			}
+		case reflect.Int:
+			i := newField.Int()
+			if i != 0 {
+				oldField.SetInt(i)
+			}
+		}
+	}
+}