Creating multiline login banners

In a number of Mac environments, there is a need or requirement for a login banner (otherwise known as a lock message). This message appears in the following locations:

• FileVault 2 pre-boot login screen
• OS login window
• Screensaver lock window

Brevity is best, as staying within a maximum of three lines permits the banner text to be displayed consistently in all three locations. Exceeding the three-line limit may result in the text being cut off and not fully displayed.

You can set this banner text from the command line using the following defaults command, which should be run with root privileges:

/usr/bin/defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText "My Login Window Text Goes Here"

Being able to consistently set when lines begin and end can be challenging though, as the defaults command is not able to interpret a newline command natively. However, it is possible to set a multi-line login banner and be able to consistently set when lines begin and end. For more details, see below the jump.

To accommodate for the defaults command’s inability to interpret newline commands, you can use the printf utility to format the text of the login banner as designed and store the formatted text as a variable. printf is able to interpret the characters \n as indicating a carriage return, so it is possible to run the following command:

printf "This Mac belongs to John Doe\nPhone number: 1-555-555-1212\nReward offered if found.\n"

To display the following text:

This Mac belongs to John Doe
Phone number: 1-555-555-1212
Reward offered if found.

In order to set a login banner with this message, you could run a script like the one shown below, using root privileges:

#!/bin/bash

loginbannertext=`printf "This Mac belongs to John Doe\nPhone number: 1-555-555-1212\nReward offered if found."`

# Set login banner

/usr/bin/defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText "$loginbannertext"

The message will appear at the login window,  screensaver lock window, and FileVault 2 login with the desired lines of text beginning and ending as specified.

Note: If the message does not appear at the FileVault 2 login, you also need to remove certain cache filenames ending in .efires from the following location:

/System/Library/Caches/com.apple.corestorage/EFILoginLocalizations