I tried to share the root / from a fedora 9 to a freeBSD while when I tried to mount the / folder it complained with "[tcp] nfs_server:/: RPCPROG_NFS: RPC: Program not registered". I followed the below steps to setup on the fedora nfs server:-

Add the below line inside the /etc/exports

/       nfs_client(rw,no_root_squash,sync)

restart the nfs related service

service portmapper restart
service nfslock restart
service nfs restart

export the filesystem using the below command:-

exportfs -arv

On the nfs client, I have troubleshoot using the below command:-

rpcinfo -p nfs_server
   program vers proto   port  service
    100000    2   tcp    111  rpcbind
    100000    2   udp    111  rpcbind
    100024    1   udp  32816  status
    100024    1   tcp  34173  status
    100011    1   udp    817  rquotad
    100011    2   udp    817  rquotad
    100011    1   tcp    820  rquotad
    100011    2   tcp    820  rquotad
    100003    2   udp   2049  nfs
    100003    3   udp   2049  nfs
    100021    1   udp  32818  nlockmgr
    100021    3   udp  32818  nlockmgr
    100021    4   udp  32818  nlockmgr
    100005    1   udp  32819  mountd
    100005    1   tcp  34174  mountd
    100005    2   udp  32819  mountd
    100005    2   tcp  34174  mountd
    100005    3   udp  32819  mountd
    100005    3   tcp  34174  mountd


showmount -e nfs_client
Exports list on nfs_server:
/                                  nfs_client

What else did I missed?