Are you following this:

https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Desktop_Migration_and_Administration_Guide/customizing-login-screen.html

?

The:

#dconf update

Is a crucial step.

On Thu, Oct 15, 2015 at 6:35 AM, Stephen Berg (Contractor) <
[log in to unmask]> wrote:

> I've tried to set this up a couple times and somehow I get no banner
> display at all.
>
> On an idle desktop I set the following by running dconf-editor as root,
> made sure the system was up to date (SL7.1) and rebooted it. When the login
> screen came up all I get is the two most recent users listed.  No banner at
> all.  So it's not showing the banner and it is showing the recent user's.
> I've looked into this issue a few times but never found a solution, so it's
> probably something really simple and silly that I'm missing.
>
> [org/gnome/login-screen]
> banner-message-enable=true
> banner-message-text='You are accessing a U.S. Government (USG) Information
> (...snip...)'
> disable-user-list=true
> enable-fingerprint-authentication=false
>
> --
> Stephen Berg
> Systems Administrator
> NRL Code: 7320
> Office: 228-688-5738
> [log in to unmask]
>



-- 
Miano, Steven M.
http://stevenmiano.com