Pre login banner is use for sending a warning message before authentication may be relevant for getting legal protection or just give out information to users. The contents of the specified file are sent to the remote user before authentication is allowed. This option is only available for protocol version 2. By default, no banner is displayed (if you are using latest version of Linux/UNIX then you do not have to worry about version issue).
Procedure to change OpenSSH pre login banner
1) By default sshd server turns off this feature.
2) Login as the root user; create your login banner file:
# vi /etc/ssh/sshd-banner
Welcome to nixCraft Remote Login!
3) Open sshd configuration file /etc/sshd/sshd_config using a text editor:
# vi /etc/sshd/sshd_config
4) Add/edit the following line:
5) Save file and restart the sshd server:
# /etc/init.d/sshd restart