Our login screen requirements include a warning / disclaimer and a basic login, showing just a username and password field. Sadly, Gnome 3 seems to be ignoring the org.gnome.login-screen.disable-user-list checkbox presented by dconf-editor.
Can you disable the list of users displayed prior to login in Gnome 3 GDM?
gdm3 loads its configuration in its own dconf database. This is separate apparently from the user dconf db that is accessible from the GUI with dconf-editor.
To edit the key value pairs which control the gdm settings and the login screen create a custom file in the /etc/dconf/db/gdm.d and add the custom entries there.
Do the following as the root user:
Add the following:
[org/gnome/login-screen]
disable-user-list=true
Update the dconf database
dconf update
Restart gdm.
systemctl restart gdm
or
/etc/init.d/gdm restart
More details on this can be found on the gnome sysadmin FAQ.
This is what worked for me (Oracle Linux 6.5)
http://blog.toracat.org/2011/01/gnome-login-shows-all-valid-user-accounts-disable-it/
Edit the /etc/gconf/gconf.xml.defaults/%gconf-tree.xml file
Under this section
<entry name="disable_user_list" mtime="1400746800" type="schema" stype="bool" owner="gdm-simple-greeter" gettext_domain="gdm"
<local_schema locale="C" short_desc="Do not show known users in the login window">
<default type="bool" value="false"/>
<longdesc>Set to true to disable showing known users in the login window.</longdesc>
</local_schema>
</entry>
Change false to true and logout.
