mount.nfs: Input/output error When Mounting From CentOS 5.9 to 6.4

Was trying to mount a NFS shared folder on CentOS 6.4 from CentOS 5.9 and found a really tricky problem. I’ve added the /etc/fstab entry, but once I ran mount /my/folder it stuck for 2-3 minutes and came back saying

mount.nfs: Input/output error

Things I’ve Tried

This is all the things I’ve tried with no success:

  • Ensured network connection was ok. I checked the firewall / iptables and made sure the client machine can connect to NFS server
  • Checked my /etc/hosts file, ensured no dodgy entries
  • Double checked /etc/exports and ran exportfs -r on the NFS server
  • Ran showmount -e [host_ip] to check the NFS server really does advertise the shared folders
  • Ran rpcinfo -p [host_ip] to check the version and supporting services are available
  • Rebooting the server many times


Thanks to this post from forum, the solution was to add nolock option to the /etc/fstab file. /mnt/nfs/my/folder nfs nolock 0 0

CentOS manual is pretty vague as well on what this option really does, but oh well it seems to do the job for time being

nolock — Disables file locking. This setting is occasionally required when connecting to older NFS servers.


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