Hai , i am using redhat linux7.3

what is the diffrence between Nfs sever and telnet,ssh commends?.

I think they are work same function.

How to add directory to /etc/exports file with out using text editor?.

The linuxconf command is used to add directory to /etc/exports file on redhatlinux7.2 but linuxconf command is not avilable in redhatlinux7.3 .which commad is used for alternate on linux7.3

First and formost: use ssh whenever you can. Very important if
you don't want your passwords not to be compromised. Now
I don't know about Nfs, but about the differences between telnet
and ssh, well, practically telnet just opens a line of communication
between two computers.
Data send by telnet are not encrypted, thus, anyone spying
on the line can see anything you type/do: passwords, commands,
actions ... everything (feel confortable??). Ssh on the other hand uses
encryption and authentication procedures for obvious reasons. It's
definatelly more secure and sophisticated and thus it feels "slower"
than telnet. But knowing the above it worths it, right??

Cheers,
Dominique

echo "/usr/local *.domain.COM(all_squash,ro,sync)" >> /etc/exports