"mount: RPC: Timed out" when attempting to mount NFS filesystem

Following a reboot of an NFS server, client machines are unable to mount it, returning the message"mount: RPC: Timed out"

• I've ruled out iptables rules by clearing them
• /etc/exports on the server is unchanged
• rpcinfo -p from the client to the server looks OK:

    program vers proto   port
    100000    2   tcp    111  portmapper
    100000    2   udp    111  portmapper
    100003    2   udp   2049  nfs
    100003    3   udp   2049  nfs
    100003    2   tcp   2049  nfs
    100003    3   tcp   2049  nfs
    100021    1   udp  32791  nlockmgr
    100021    3   udp  32791  nlockmgr
    100021    4   udp  32791  nlockmgr
    100021    1   tcp  32768  nlockmgr
    100021    3   tcp  32768  nlockmgr
    100021    4   tcp  32768  nlockmgr
    100005    1   udp    618  mountd
    100005    1   tcp    621  mountd
    100005    2   udp    618  mountd
    100005    2   tcp    621  mountd
    100005    3   udp    618  mountd
    100005    3   tcp    621  mountd
    100024    1   udp  32765  status
    100024    1   tcp  32765  status

Advice for further diagnostics much appreciated!

From serverfault Paul Dixon

• I resolved this by restarting some of the client side components with

  /etc/init.d/nfs-common restart
  

  I was then able to mount the filesystem just fine. Phew ;)

  From Paul Dixon

• You need to make sure that both the client and the server have a working portmap service, visible from the client. It's possible that you don't have a working portmap on the client.

  From David Pashley