To add a Message of the Day:
1.) Open Terminal and enter the following command.
sudo vim /etc/motd
Since we are not logged into the Root User, we have to precede the command with a sudo, this then prompts you, asking for your administrative password.
(Also Note: that you can use any editor of your choice, now that I know a few of the shortcuts for vim, it is starting to grow on me. "Nano" is also a very easy Text Editor, and the shortcuts are all displayed at the bottom of the screen for your convenience.)
2.) Once you have entered vim, press "
i" to enter the "Input mode" and type whatever you'd like for your message of the day. Example: "
Welcome to Darwin!"
Escto exit out of "Input mode" and type: "
:wq" (explained in this post) to save the file.
4.) Now close and re-open Terminal and you'll now see your new Message of the Day!