The abbreviation "motd" stands for "message of the day", and this file has been traditionally used for exactly that (it requires much less disk space than mail to all users). To change what your current message reads, you need to edit /etc/motd file. Now whenever your users login, they will be see whatever you have placed in this file.
The message of the day can be used to communicate important information about your
server to end users, or to remind users something important.
To change what your current message, you need to edit /etc/motd file using text editor such as vi. For example display following messge to all users:
# vi /etc/motd
Add following sample message to it (remove existing message):
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