Get notified instantly when someone logs into your server as root. Here is how to do it.
1st. Login as root in console, for ubuntu its sudo -i and for other distributions its simply su.
2nd. Edit your root bash file by typing: nano /root/.bashrc
3rd. Place this following code snippet at the bottom of the file (make sure to replace YourServerName and email with your own)
echo 'ALERT - Root Shell Access (YourServerName) on:' `date` `who` | mail -s "Alert: Root Access from `who | cut -d"(" -f2 | cut -d")" -f1`" your_email@your_domain.com
This it. Now if your email server such as sendmail installed, you should receive root login notifications.