How to change the message display upon login

There are some message display after a successful log into the system. e.g. (if your system is running Ubuntu)

"The programs included with the Ubuntu system are free software; the 
exact distribution terms for each program are described in the 
individual files in /usr/share/doc/*/copyright.

Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted 
by applicable law.

To access official Ubuntu documentation, please visit: 
http://help.ubuntu.com/"

The message is called "message of the day", aka, motd. It is a text file store at /etc/motd , but it is replace with the copy at /etc/motd.tail on Linux. Change the file with the message you want using vi or other editor of your choice.

Below are some escape codes to display some additional info :

\b = Insert the baudrate of the current line.
\d = Insert the current date.
\s = Insert the system name, the name of the operating system.
\l = Insert the name of the current tty line.
\m = Insert the architecture identifier of the machine, eg. i486
\n = Insert  the nodename of the machine, also known as the hostname.
\o = Insert the NIS domainname of the machine.
\O = Insert the DNS domainname of the machine.
\r = Insert the release number of the OS, eg. 1.1.9.
\t = Insert the current time.
\u = Insert the number of current users logged in.
\U = Insert the string "1 user" or "<n> users" where <n> is the number
of users login.

Ciao !!!