Right click on a panel and add a 'Custom Application Launcher'
Type as follows:
Name: GKSudo launcher
Command: gksudo "gnome-open %u"
Comment: Open files with root privilege
Then choose the icon of your liking.
When you're done with that you can just drag a file onto that icon and it will open it with root access; like the file called 'root' in your system files. You would get this message:
but if you just drag the file onto the icon it will go away
Bookmarks