You don't need the installation media. If you have access to the server console you can add the word single at the end of the kernel parameter line in the Grub startup menu. This will prompt you at the command shell, from where you can type the command passwd to change the root password, then restart the system and everything should be as usual.
Your duplicate post that you had placed into the SQL-PL/SQL forum has been removed.
Why you would have dreamed of putting an OS question over there is a bit perplexing.
(at least until reviewing posting history and noticing they're all questions easily answered by using Google)