Modding the Mac OS to suit your needs is common around these parts, but there is one area that often times overlooked.  The Login Window.  The usual way to modify something like this is to edit the .nib file that is called when logging in, but that is a separate story.  If you know how to edit the NIB file it is located in /System/Library/CoreServices/SecurityAgentPlugins/loginwindow.bundle/Contents/Resources/English.lproj.  However, if you've never worked on a NIB before, there is an easier way after the jump.


Mac OS X has a built-in option for the welcome message.  By editing the com.apple.loginwindow.plist file inside of /Library/Preferences.  Your two options are to edit this via the command line or with a plist editor (like the one that comes with the Developers tools, XCode).  PrefSetter is an application from Night Productions (nightproductions.net) that allows you to open and save any of your preference files.  Plist Editor is the freebie with XCode.  There are some retail applications that will allow you to edit the plist files, but I prefer the free.

Once you have the plist editor, open the com.apple.loginwindow plist file and add a "LoginwindowText" key.  Make it a string value and add whatever you want to appear in your login window.  Either save a copy of the plist to the Desktop and copy it over, or save directly back into the Preferences folder.  No need to restart, just go back to the login window (either log out or via the fast user switching) and it should show up there.

Finally you can also use the terminal to do it.  By doing a defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText "This is your welcome message" you can define the welcome message.  However, it must be in quotes when you do it this way and it isn't as forgiving.  I got an error message when I tried putting in three paragraphs for the welcome message this way, but editing the plist worked.  And no.  Don't ask why I would want three paragraphs for my welcome message.  Let's just say I have a lot to say.

Download PrefSetter from Night Productions here.