When i'm log in to the RHEL 4 box from one tty,
it is not taking any username and password, even root also.
no error is displayed, when i entered username and password again and again it asking me for username and password.

I think this the the problem of nologin file.

Please tell me about nologin file and help me to resolved this issue.

thanks....

Sunny Anthony

quoting the login man:
So that realy cant be the cause of your problem if root cannot login. Is it possible that your harddrive is full? Thats the single thing that causes the most weird of errors since no pid files, temp files etc etc can be placed normaly.

If this is the case and you cannot log in, I suggest you boot the machine off a livedisk or minidistro and clean out some logfiles etc unneeded files.

Another problem that can cause the symptoms you describe is that the machine has pam installed and /etc/securetty doesnt have the tty:s listed. This will prevent root logins, but as I remember normal users ought to be able to log in.