I have two RHEL5 boxes on a private network together ( and I am trying to export a file system from one to the other but I keep getting the following error:

mount.nfs: Input/output error

on the client side I see this output:

mount: trying prog 100003 vers 3 prot tcp port 2049
mount: trying prog 100005 vers 3 prot tcp port 960

and on the server side I see this:

Sep 20 14:14:32 omicron mountd[18739]: authenticated mount request from for /srv/nfs/web (/srv/nfs/web)

but that's all. I opened up iptables so that the whole network is allowed to communicate freely but the public side is locked down to 22,80 etc....

any ideas?


I had a similar problem, please have a look at this link.
And this one.

Basically you have to open much more ports.


Make sure portmapper is running

On centos

chkconfig --list | grep portmap

To start it on centos and set it to start at boot

service portmap start
chkconfig portmap on

For a similar problem, I have added to the syntax of the mount command the following options "-o nolock, udp."

mount -o nolock,udp /mnt/nfs/

Apparently this problem when the service nfslook is not 'started' successfully.


Check the following:

  • On the server, can you read/write to and from /srv/nfs/web?
  • What's in your /etc/exports?
  • What's in /etc/hosts.*
  • What's in your /etc/sysconfig/iptables?
  • What happens if you service iptables stop on both hosts and then try to mount it?
  • The directory where you're trying to mount it you have read/write access to?
  • What mount options are you using/what is the line in /etc/fstab for the mount?
  • What is the output from 'showmount -a' and 'showmount -e'?
  • 1
    That should be in the comments, not in the answers. – Rilindo Nov 30 '11 at 4:13

Please also note portsentry maybe running, disable it and restart portmap

# /etc/init.d/portmap status
portmap dead but subsys locked
# /etc/init.d/portsentry stop
chkconfig portsentry off
# /etc/init.d/portmap start     
Starting portmap:                                          [  OK  ]

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