Ubuntu does not have the option open a file as administrator from file manager by default. But we will this option most of the times to edit system files to tweak the operating system to our needs. We can add this option in three simple steps.
Step 1.a: Ubuntu 12.04
Here are the steps to do that:
sudo apt-add-repository ppa:upubuntu-com/ppa
sudo apt-get update
sudo apt-get install nautilus-gksu
Step 1.b: Ubuntu 14.04
Here are the steps to do that:
sudo add-apt-repository ppa:noobslab/apps
sudo apt-get update
sudo apt-get install open-as-administrator
Step 2
After doing this, restart nautilus file manager using the command
killall nautilus && nautilus &
Now go to your file manager and you will be able to open any file/folder as administrator in your favourite application. You don't have to open terminal for this anymore. Feel free to post your comments.