Clear console screen before logon prompt

The easiest way of clearing screen before logon (or after logout) is to put a "clear" escape sequence into /etc/issue. The following command add it to the end of the file.

clear >> /etc/issue

Now use your favorite editor (vim) and ensure that ^[[H^[[2J is at the beginning. Here is an example:

^[[H^[[2JDebian GNU/Linux 5.0 \n \l

Read more about this here.