[lubuntu] What is my Root password ?

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http://ubuntuforums.org – I just installed Lubuntu as a user. It didn't ask me anything during the install about root, or what root password I would like. So now, when I need root to change /etc/fstab or /etc/rc.local, I can't. When I try to set up root admin in Users Accounts, it says there already is a root. Nobody said nothing to ME about setting up a root account. I'm just the owner of this computer, and the installer of Lubuntu. Why should I be told about anything... So how do I find out what my root's password is ? (Hardware)