default root password for ubuntu 12.04

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http://askubuntu.com – I installed Ubuntu 64bit 12.04. nowhere was asked to set password for root. I just installed AccuRev software. It was installed under the root folder by default. Now I try do something on that folder. I tried with su to switch to root but I don't know its password. Always use sudo or get the default root password if any? EDIT: how to create launcher for software installed inside root directory? (HowTos)