How can I add a custom message in the macOS login screen?

Question

Our community group has just had three Apple Macs donated to us. Two are laptops with macOS Sierra installed and one is an iMac with macOS High Sierra installed.

I’ve been asked to add a custom message to the login screen acknowledging the donation, but I am not familiar with Apple Macs. It only needs to be a simple message like:

This Mac was kindly donated by X.

Is there a way of doing this without having to use any 3rd party software? I would need some very clear steps.

Answer 1

This can be done without 3rd party app. Simply open System Preferences.app -> Security & Privacy -> Show message when the screen is locked. Here are the steps:

1. Open "System Preferences" (located in you applications folder)
2. Select "Security & Privacy"
3. Unlock the padlock
4. Set the lock message

Answer 2

Yes, you can do this by using Terminal. More specifically:

1. Open the Terminal app (by default this is located in the Utilities folder within your Applications folder)

2. Now copy the following command and paste it into your Terminal window:

   sudo defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText "This Mac was kindly donated by X."

3. Now press the delete key a few times to remove the X

4. Type in the rest of your custom message. Make sure you close it off with the second quotation mark at the end.
5. Press the enter key
6. You’ll be prompted for your password. Type it in and press the enter key again (Note: You will not see the cursor move or the password on the screen)

Now when you’re back on the login screen you will see your custom message displayed below your list of users.

Answer 3

In the Terminal:

sudo defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText "Your Message Here"

Answer 4

Via GUI

You can do this via System Preferences -> Security & Privacy -> General, see How to set a lock message on the login window of your Mac for details.

Via Command Line

sudo defaults write /Library/Preferences/com.apple.loginwindow LoginwindowText "The Custom Message here. 
    The message can be multi-line as well and will work fine"

As a policy banner

You can also set a policy banner by following this instructions from Apple

• Create a plain text (.txt) or rich text (.rtf) document that contains your banner.
• Choose File > Save, then enter PolicyBanner for the document name.
• Copy the PolicyBanner file to the /Library/Security/ folder.
• Run chmod o+r /Library/Security/PolicyBanner.txt

This may be useful for people who wanted to show the custom message on lock screen due to reasons like when their Mac is lost then they can display a contact number. Because the custom message of login window seems to be displayed only when we login-in and then lock the screen. During initial login, the custom message is not displayed. (Probably because this custom message is user specific and not applicable to all the users).