Ubuntu: Use root password instead default user password

After clean install of Ubuntu, you noticed u have to enter your user password to do administrative or system tasks. This is the way to change it.
First make sure u set password for the 'root' user:

sudo passwd root

Use your favorite text editor and edit '/usr/share/gconf/defaults/10_libgksu' file.
Change:

/apps/gksu/sudo-mode true

to:

/apps/gksu/sudo-mode false

Then issue following command:

sudo update-gconf-defaults