diff --git a/config/config.toml b/config/config.toml
index ac0aab9..d3faf17 100644
--- a/config/config.toml
+++ b/config/config.toml
@@ -13,6 +13,7 @@ data_dir = "/tmp/ledis_server"
 access_log = ""
 
 # Set slaveof to enable replication from master, empty, no replication
+# Any write operations except flushall and replication will be disabled in slave mode.
 slaveof = ""
 
 # Choose which backend storage to use, now support:
diff --git a/ledis/ledis.go b/ledis/ledis.go
index 27f2ad3..0052b3a 100644
--- a/ledis/ledis.go
+++ b/ledis/ledis.go
@@ -33,7 +33,7 @@ type Ledis struct {
 	wLock      sync.RWMutex //allow one write at same time
 	commitLock sync.Mutex   //allow one write commit at same time
 
-	// for readonly mode, only replication can write
+	// for readonly mode, only replication and flushall can write
 	readOnly bool
 
 	lock io.Closer
diff --git a/server/app.go b/server/app.go
index 74a0b23..62f8514 100644
--- a/server/app.go
+++ b/server/app.go
@@ -88,7 +88,13 @@ func NewApp(cfg *config.Config) (*App, error) {
 		}
 	}
 
-	if app.ldb, err = ledis.Open(cfg); err != nil {
+	flag := ledis.RDWRMode
+	if len(app.cfg.SlaveOf) > 0 {
+		//slave must readonly
+		flag = ledis.ROnlyMode
+	}
+
+	if app.ldb, err = ledis.Open2(cfg, flag); err != nil {
 		return nil, err
 	}
 
diff --git a/server/cmd_server.go b/server/cmd_server.go
index 1d7a1cb..ab8051f 100644
--- a/server/cmd_server.go
+++ b/server/cmd_server.go
@@ -82,20 +82,6 @@ func flushdbCommand(c *client) error {
 	return nil
 }
 
-func readonlyCommand(c *client) error {
-	if len(c.args) != 1 {
-		return ErrCmdParams
-	}
-
-	if flag, err := strconv.Atoi(hack.String(c.args[0])); err != nil {
-		return err
-	} else {
-		c.app.ldb.SetReadOnly(flag != 0)
-		c.resp.writeStatus(OK)
-	}
-	return nil
-}
-
 func init() {
 	register("ping", pingCommand)
 	register("echo", echoCommand)
diff --git a/server/replication.go b/server/replication.go
index d90caab..8d49f43 100644
--- a/server/replication.go
+++ b/server/replication.go
@@ -87,8 +87,6 @@ func (m *master) connect() error {
 func (m *master) stopReplication() error {
 	m.Close()
 
-	m.app.ldb.SetReadOnly(false)
-
 	return nil
 }
 
@@ -126,7 +124,7 @@ func (m *master) runReplication() {
 			if err := m.sync(); err != nil {
 				if m.conn != nil {
 					//if conn == nil, other close the replication, not error
-					log.Warn("sync error %s", err.Error())
+					log.Error("sync error %s", err.Error())
 				}
 				return
 			}
@@ -237,7 +235,11 @@ func (app *App) slaveof(masterAddr string) error {
 	}
 
 	if len(masterAddr) == 0 {
-		return app.m.stopReplication()
+		if err := app.m.stopReplication(); err != nil {
+			return err
+		}
+
+		app.ldb.SetReadOnly(false)
 	} else {
 		return app.m.startReplication(masterAddr)
 	}