Being a complete novice in Linux, I don’t yet know how to do many obvious things. For example, I thought that the notorious ‘root’ thing should be installed. Upon googling for ‘install root’, I have found a command
sudo apt-get install root-system-bin
which I happily executed. Of course, instead of giving me the root rights, it has installed the ROOT’s Object Oriented Technologies thing, which has appeared in the Ubuntu Software Center. I have then tried to uninstall it using the Remove button there. Ubuntu has asked me for the password but has not removed anything, the ROOT was still there.
The solution came in the form of the terminal command
sudo apt-get remove root-system-bin
After this, ROOT also nicely disappears from the list of installed programmes in the Ubuntu Software Centre.
Hint: Following a colleague’s advice, I have also executed
sudo apt-get remove root-system-bin --purge
sudo apt-get autoremove
This removes many installed and no more needed files.