use two pc: online01 online03
set online01(rh9) as dhcp,tftp,nfs server.
online01 /etc/exports:
/tftpboo/online03 *(rw,no_root_squash)
/usr *(rw,no_root_squash)

kernel 2.4.20-8 for online03:
dhcp,bootp,rarp,nfsroot buildin.

online03 /etc/fstab:
online01:/ftfpboot/online03 / nfs defaults 0 0
online01:/usr /usr nfs defaults 0 0

both side has portmap runing.

when online03 boot up as diskless client (run level 1):
(during booting get error: " portmap: spcecial device online01:/usr does not exist" )
df:
online01:/ftfpboot/online03 /
(/usr is not mounted, ls /usr returns nothing)

but, showmount -a online01
online03.online.local:/tftpboot/online03
online03.online.local:/usr

why cant /usr be mounted ?

The firewall on online03 is blocking access?

no firewall working on online03.

the problem gone after i add (rw) in pxeconfig file's append line.

thanks anyway!

no prob - good to see you posting the solution you found.
Well done.