Cannot ssh for a user

Linux and Unix-Like Red Hat
1

This is the entry when I tail /var/log/secure when I ssh for user "nightly"...

 
Aug  4 03:19:48 itanium2 sshd[10791]: Illegal user nightly from ::ffff:10.91.220.35
Aug  4 03:20:10 itanium2 sshd[10791]: Failed password for illegal user nightly from ::ffff:10.91.220.35 port 32862 ssh2

What could be the reason, plz suggest.

---------- Post updated at 07:48 PM ---------- Previous update was at 07:42 PM ----------

and password is correct, works when I telnet, just ssh fails.

---------- Post updated at 07:50 PM ---------- Previous update was at 07:48 PM ----------

there is a local user for the host with which I can ssh to the system but not with nightly. nightly is not in /etc/passwd

2

If nightly is not in /etc/passwd, how is nightly being authenticated? NIS, LDAP or what?

3

yes, it was an NIS user.
and the IP settings of the server was changed.
So the keys got messy.
I disabled the PubkeyAuthentication option in /etc/ssh/sshd_config
Now I can login, but i need to regenrate the keys

4

use ssh-key gen command to generate the keys