I'm trying to configure the /etc/sudoers file to allow a non-administrative user access to certain applications, namely the Update Manager and Ubuntu Software Centre.

I configure the file as follows. The host's name is 'ubuntu', 'luser' is the administrative user and 'mark' is the one I want to grant the necessary privileges to.

Code:
Defaults	env_reset
Defaults	secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
root	ALL=(ALL:ALL) ALL
mark ubuntu=(ALL)NOPASSWD:/usr/bin/software-center,/usr/bin/update-manager
%admin ALL=(ALL) ALL
%sudo	ALL=(ALL:ALL) ALL
As you can see, the file contains the default config plus my 1 extra line.

If you log in as user 'mark' and run
Code:
sudo update-manager
or
Code:
sudo software-center
, I am able to run these with the expected privileges. However, if I run the applications from the Unity menus or dash, it doesn't run with elevated privilege and asks for authentication. It won't accept the password for the 'mark' user but it will accept the password for 'luser' which is the one I used when I installed Ubuntu.

I can't figure out what else I need to do, to make sudo work for the graphical interface. Can anyone help me out?

Thanks