Software management on Ubuntu 12.10

Complementing Package Sources

In Software Center, you can download from external repositories using Edit | Software Sources. To use the Medibuntu project's external sources, for example, click Other Software and Add, then enter deb http://packages.medibuntu.org/ quantal free non-free. This address is not the actual one; usually, the address is the website for the external repository. Click the Add Source button to accept the repository (Figure 6).

Figure 6: Obtain additional packages from external repositories.

External repositories often protect themselves from abuse with keys, and this applies to Medibuntu sources as well. Every package has a signature verified with a key, so manipulated packages with mismatched signatures will fall by the wayside. Often, you can't access a package offering without a key, but how do get one? To import the key for the Medibuntu repository, invoke a terminal through Ctrl+Alt+T and use the following command:

$ sudo apt-get update

The command updates the list of available software for Software Center and returns an error message. Next, enter the following command:

$ sudo apt-key adv --recv-keys --keyserver hkp://keyserver.ubuntu.com:80 2EBC26B60C5A2783

This downloads the appropriate key and integrates it with package management. If you can't get to the keyserver, it may be temporarily overloaded. In this case, replace keyserver.ubuntu.com in the command with another keyserver, such as subkeys.pgp.net, pgp.mit.edu, or keys.gnupg.net. After entering the sudo apt-get update command, you should be able to install the software from the source. The new repository might not show up in Software Center right away.

Key Over Terminal

Importing the key can be handled another way. Most websites show a simple line that you can copy with Ctrl+C and Ctrl+V to the terminal. The line might appear as in the following VirtualBox example:

$ wget -q http://download.virtualbox.org/virtualbox/debian/oracle_vbox.asc-O - | sudo apt-key add -

This command downloads the key from the website (using wget -q {HTTP-LINK}), sends it to the console (with -O -), and passes it to the sudo apt-key add command. Next, use sudo apt-get update to update the package list and load up the VirtualBox package.