In addition to the officially supported package repositories available for Ubuntu, there exist additional community-maintained repositories which add thousands more potential packages for installation. Two of the most popular are the Universe and Multiverse repositories. These repositories are not officially supported by Ubuntu, but because they are maintained by the community they generally provide packages which are safe for use with your Ubuntu computer.

Many other package sources are available, sometimes even offering only one package, as in the case of package sources provided by the developer of a single application. You should always be very careful and cautious when using non-standard package sources, however. Research the source and packages carefully before performing any installation, as some package sources and their packages could render your system unstable or non-functional in some respects.

By default, the Universe and Multiverse repositories are enabled but if you would like to disable them edit /etc/apt/sources.list and comment the following lines:

deb http://archive.ubuntu.com/ubuntu hardy universe multiverse deb-src http://archive.ubuntu.com/ubuntu hardy universe multiverse deb http://us.archive.ubuntu.com/ubuntu/ hardy universe deb-src http://us.archive.ubuntu.com/ubuntu/ hardy universe deb http://us.archive.ubuntu.com/ubuntu/ hardy-updates universe deb-src http://us.archive.ubuntu.com/ubuntu/ hardy-updates universe deb http://us.archive.ubuntu.com/ubuntu/ hardy multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ hardy multiverse deb http://us.archive.ubuntu.com/ubuntu/ hardy-updates multiverse deb-src http://us.archive.ubuntu.com/ubuntu/ hardy-updates multiverse deb http://security.ubuntu.com/ubuntu hardy-security universe deb-src http://security.ubuntu.com/ubuntu hardy-security universe deb http://security.ubuntu.com/ubuntu hardy-security multiverse deb-src http://security.ubuntu.com/ubuntu hardy-security multiverse