nfs and telnet problems

[Adel Essafi]

hi lists
I have installed an FC4 server. I have confgured it as nis and NFS 
servers. I have proceeded exactly like documentation said and I got 
theses probles
(note that ping and ssh works well)
1- telnet don t work
2. nfs don t show the partitions to export (exportfs -a  returns nothing)
3. (not important at this point) nis clients can t find the server.
I don t know why this happens. I have tested this 5 months ago with an 
FC3 and it works fine   :-\
could you help plz