When we’re deploying Mac OS X there are a number of things that invariably end up being discussed. One of these is customizing the login window, where you type in your username and password. This might be swapping out the background of the screen, adding text or even changing out the Apple logo.
To change out the background of the loginwindow, you can specify a new location. By default the location is stored in /System/Library/CoreServices as DefaultDesktop.jpg. You could replace this image or the preferred method would more than likely be to choose your image and then alter the /Library/Preferences/com.apple.loginwindow.plist, editing the key for DesktopPicture. For example, we can use the defaults command to edit the appropriate key to be myimage.jpg in a folder called Custom on the root of the drive:
defaults write /Library/Preferences/com.apple.loginwindow DesktopPicture ‘/Custom/myimage.jpg’
To then go back to the original background with the default image from Apple you can use the following command (not having a key means that Mac OS X will use the original image):
defaults delete /Library/Preferences/com.apple.loginwindow DesktopPicture
You can also edit the text displayed at the login window, above the list of users. This is a good place to remind users of acceptable use policies, announce items from IT or display a number of strings to users who might happen across the computer. To add the text
defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText “By logging into this computer you are accepting the terms of our Acceptable Use Policy, which can be found at http://internal.krypted.com/Use.pdf”
If you would like to go back to the system defaults, again delete the key:
defaults delete /Library/Preferences/com.apple.loginwindow LoginwindowText
You can also replace the Apple logo that appears at the top of the login window with a different tif (should be 90×90 pxls). To do so, browse into the SecurityAgent.app at /System/Library/CoreServices/SecurityAgent.app/Contents/Resources/
and replace applelogo.tif. This can be useful for displaying a schools mascot or a companies logo, but has little other purpose beyond branding that I can think of. I usually rename the existing tif and add a new one. To rename:
mv /System/Library/CoreServices/SecurityAgent.app/Contents/Resources/applelogo.tif /System/Library/CoreServices/SecurityAgent.app/Contents/Resources/applelogo.tif.OLD
Then to copy an image called mylogo.tif from your desktop to the appropriate location:
cp ~/mylogo.tif /System/Library/CoreServices/SecurityAgent.app/Contents/Resources/applelogo.tif
To revert back you would simply mv the new applelog.tif and then rename the old one back. Once you’ve customized the loginwindow itself, another aspect of the login process that many will move into customizing is what happens immediately following the login event, in many cases using login hooks.
