How to reset root Password Ubuntu & Fedora

Lost your root password?

If you have lost your root password, you can’t really recover it, but you can change it if you have physical access to the machine.

The two most used methods of changing your root password if it’s lost is:
Booting into single-user mode and resetting the password
Booting from a live CD and [...]

Error cannot retrieve repository metadata repomd.xml for repository

You need to edit two of your repository files: /etc/yum.repos.d/fedora.repo and /etc/yum.repos.d/fedora-updates.repo. Now un-comment all the lines that start with the term baseurl and place a comment before all lines that start with mirrorlist. This should be done for both the above files.
Now edit your /etc/hosts file and append the following to it’s contents:
80.239.156.215 [...]

Recover Lost Data / Partitions

TestDisk is a powerful free data recovery software! It was primarily designed to help recover lost partitions and/or make non-booting disks bootable again when these symptoms are caused by faulty software, certain types of viruses or human error (such as accidentally deleting a Partition Table). Partition table recovery using TestDisk is really easy. (read more…)

Error showing url: There was an error launching the default action command associated with this location.

I use Fedora Gnome and i solve my error going to
System->Preferences->Personal->Preferred Applications
and i choose default browser.

Callee RC: 0×80040154

Callee RC: 0×80040154 error while using Virtualbox on Fedora 9. You can fix this by removing some files from tmp directory:
sudo rm -rf /tmp/.vbox*