When Ubuntu was using gnome I was able to create a popup banner like the banner below before the login screen using zenity in the /etc/gdm/Init/Default. The line of code would be like this:
if [ -f "/usr/bin/zenity" ]; then /usr/bin/zenity --info --text="`cat /etc/issue`" --no-wrap; else xmessage -file /etc/issue -button ok -geometry 540X480; fi
How can I accomplish this with Unity?
NOTICE TO USERS
This is a Federal computer system (and/or it is directly connected to
a BNL local network system) and is the property of the United States
Government. It is for authorized use only. Users (authorized or
unauthorized) have no explicit or implicit expectation of privacy.
Any or all uses of this system and all files on this system may be
intercepted, monitored, recorded, copied, audited, inspected, and
disclosed to authorized site, Department of Energy, and law
enforcement personnel, as well as authorized officials of other
agencies, both domestic and foreign. By using this system, the user
consents to such interception, monitoring, recording, copying,
auditing, inspection, and disclosure at the discretion of authorized
site or Department of Energy personnel.
Unauthorized or improper use of this system may result in
administrative disciplinary action and civil and criminal penalties.
By continuing to use this system you indicate your awareness of and
consent to these terms and conditions of use.
LOG OFF IMMEDIATELY if you do not agree to the conditions stated in
this warning.