server localhost not responding, timed out

nfs mount时遇到错误：

rpcbind: server localhost not responding, timed out
RPC: failed to contact local rpcbind server (errno 5).
rpcbind: server localhost not responding, timed out
RPC: failed to contact local rpcbind server (errno 5).
lockd_up: makesock failed, error=-5
rpcbind: server localhost not responding, timed out
RPC: failed to contact local rpcbind server (errno 5).

在网上找到解决方法是在mount时加上了-o nolock选项，问题解决了。

mount -o nolock ip:/dir /mnt

具体原因：man mount（for nfs 段）说：do not use locking.Do not start lockd.

不是很明白。