Customizing the OS X login screen

Changing the Background
The background image can be changed by simply replacing the file. In Leopard, the default background is located in /System/Library/CoreServices/DefaultDesktop.jpg. In Tiger, the file is /Library/Desktop Pictures/Aqua Blue.jpg. Rename the default to a different name and copy your file of choice over the original file.
















Customizing Users
There are many tweaks one can make to the user list. Say you want to create an invisible user only accessible via SSH. Or to hide all users with certain UIDs, or hide the Other user once the root account has been enabled.

First, if you mess up something too badly, it is always possible to remove your edits by using
defaults delete /Library/Preferences/com.apple.loginwindow and
defaults delete /Library/Preferences/com.apple.loginwindow HiddenUsersList to delete users you may have hidden. Any value using TRUE may also be reversed by substituting FALSE and vice-versa.

To hide a user from the login window, use:
defaults write /Library/Preferences/com.apple.loginwindow HiddenUsersList -array-add 'jason'
You can use the user's UID instead as well. The user will also no longer appear in the Fast User Switching menu once someone has logged in.

To hide all users with UIDs under 500 -- e.g. root and the built-in Guest account:
defaults write /Library/Preferences/com.apple.loginwindow Hide500Users -bool TRUE

To hide the Other user:
defaults write /Library/Preferences/com.apple.loginwindow SHOWOTHERUSERS_MANAGED -bool FALSE

Do not try and hide all your users as this will cause the login window to be unfunctional. The login screen with the three examples shown above: