I am a linux newbie and I have a very basic question. I have three machines -

machineA    10.108.24.132
machineB    10.108.24.133
machineC    10.108.24.134

and all those machines have Ubuntu 12.04 installed in it and I have root access to all those three machines.

Now I am supposed to do below things in my above machines -

Create mount point /opt/exhibitor/conf
Mount the directory in all servers.
 sudo mount <NFS-SERVER>:/opt/exhibitor/conf /opt/exhibitor/conf/

I have already created /opt/exhibitor/conf directory in all those three machines as mentioned above.

Now I am trying to create a Mount Point on all those three machines. So I followed the below process -

Install NFS support files and NFS kernel server in all the above three machines

$ sudo apt-get install nfs-common nfs-kernel-server

Create the shared directory in all the above three machines

$ mkdir /opt/exhibitor/conf/

Edited the /etc/exports and added the entry like this in all the above three machines -

# /etc/exports: the access control list for filesystems which may be exported
#               to NFS clients.  See exports(5).
#
# Example for NFSv2 and NFSv3:
# /srv/homes       hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check)
#
# Example for NFSv4:
# /srv/nfs4        gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check)
# /srv/nfs4/homes  gss/krb5i(rw,sync,no_subtree_check)
#
/opt/exhibitor/conf/     10.108.24.*(rw)

Run exportfs in all the above three machines

root@machineA:/# exportfs -rv
exportfs: /etc/exports [1]: Neither 'subtree_check' or 'no_subtree_check' specified for export "10.108.24.*:/opt/exhibitor/conf/".
  Assuming default behaviour ('no_subtree_check').
  NOTE: this default has changed since nfs-utils version 1.0.x

exporting 10.108.24.*:/opt/exhibitor/conf

Now I did showmount on machineA

root@machineA:/# showmount -e 10.108.24.132
Export list for 10.108.24.132:
/opt/exhibitor/conf 10.108.24.*

And also I have started the NFS server like this in all the above three machines -

sudo /etc/init.d/nfs-kernel-server start    

And now when I did this, I am getting an error -

root@machineA:/# sudo mount -t nfs 10.108.24.132:/opt/exhibitor/conf /opt/exhibitor/conf/
mount.nfs: access denied by server while mounting 10.108.24.132:/opt/exhibitor/conf

I have also tried doing the same thing from machineB and machineC as well and still I get the same error-

root@machineB:/# sudo mount -t nfs 10.108.24.132:/opt/exhibitor/conf /opt/exhibitor/conf/
root@machineC:/# sudo mount -t nfs 10.108.24.132:/opt/exhibitor/conf /opt/exhibitor/conf/

Did my /etc/exports file looks good? As I have the same content in all the three machines. And also are there any logs related to NFS which I can see to find any clues?

Any idea what wrong I am doing here?

UPDATE:-

So my etc/exports files would be like this in all the three machines -

# /etc/exports: the access control list for filesystems which may be exported
#               to NFS clients.  See exports(5).
#
# Example for NFSv2 and NFSv3:
# /srv/homes       hostname1(rw,sync,no_subtree_check) hostname2(ro,sync,no_subtree_check)
#
# Example for NFSv4:
# /srv/nfs4        gss/krb5i(rw,sync,fsid=0,crossmnt,no_subtree_check)
# /srv/nfs4/homes  gss/krb5i(rw,sync,no_subtree_check)
#
/opt/exhibitor/conf/     10.108.24.132(rw)
/opt/exhibitor/conf/     10.108.24.133(rw)
/opt/exhibitor/conf/     10.108.24.134(rw)

Just a quick check - The IP Address that I am taking for each machine as mentioned above is like this -

root@machineB:/# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:50:56:ad:5b:a7
          inet addr:10.108.24.133  Bcast:10.108.27.255  Mask:255.255.252.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:5696812 errors:0 dropped:12462 overruns:0 frame:0
          TX packets:5083427 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:7904369145 (7.9 GB)  TX bytes:601844910 (601.8 MB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:187144 errors:0 dropped:0 overruns:0 frame:0
          TX packets:187144 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:24012302 (24.0 MB)  TX bytes:24012302 (24.0 MB)

Here the IP Address that I am taking for machineB is 10.108.24.133.