How to create a common user name in all the unix servers?

Hi all, Please help me with the following,

I am trying to create a common user name and password in all the UNIX servers I have.

I would like to know if I create a user name and password in a single server then an automated script or something else should run in rest of the UNIX servers, so the created user name and password is valid(or common) for all the servers.

I have seen few similarities in MS servers using WMI service with automated VB scripts performing this.

Use a Network Information Service

Thanks for the reply.

I would like to explain my situation so u can help me resolve it.

I am directly logging into a UNIX server using SSH, from there I am going to run a script which creates user in all the unix servers(lets say around 500 servers).
I got the script but the problem here is RSA authentication.
This does not allow me to run the script in the servers.

I want the script to run automatically without any restrictions.
Kindly help me with this.

You still would need to setup public key authentication on each server in order to be able to ssh from one system to another without specifying a password.

Here are some links to get you started:

http://sial.org/howto/openssh/publickey-auth/
http://www.csua.berkeley.edu/~ranga/notes/ssh_nopass.html

Your best scripting language choice would probably be expect.

This would actually allow you to not use key-based auth, but your user and root passwords would be in plain text in the script.