/ is full

/ has become full.... So i'm unable to login to the server. What should i do now ??

please help me... Thanks in advance

How do you know that / is full?
Perhaps it's out of memory?

I guess it's the file system containing / (and other (sub-) directories) that has become full. If you can't login normally anymore, try
a) to do a single user login
b) to boot a rescue disk
and delete / move out (to external drives) obsolete files in e.g. /tmp, /var, or other log file directories.
If that's impossible, show more evidence like error msgs, so we can get the whole picture.

It is recommended to use different file system for /tmp and /var in production server.

...and other servers, too.