*: support wal dir

etcdserver/server.go

@@ -189,6 +189,11 @@ func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
 		return nil, err
 	}
 
+	err = os.MkdirAll(cfg.MemberDir(), privateDirMode)
+	if err != nil && err != os.ErrExist {
+		return nil, err
+	}
+
 	haveWAL := wal.Exist(cfg.WALDir())
 	ss := snap.New(cfg.SnapDir())
 
@@ -258,6 +263,10 @@ func NewServer(cfg *ServerConfig) (*EtcdServer, error) {
 			return nil, fmt.Errorf("cannot write to member directory: %v", err)
 		}
 
+		if err := fileutil.IsDirWriteable(cfg.WALDir()); err != nil {
+			return nil, fmt.Errorf("cannot write to WAL directory: %v", err)
+		}
+
 		if cfg.ShouldDiscover() {
 			plog.Warningf("discovery token ignored since a cluster has already been initialized. Valid log found at %q", cfg.WALDir())
 		}