12.7 Summary
The Ubuntu operating system is comprised of thousands of software packages that are downloaded and installed from the main, restricted, universe, multiverse, partner and third-party repositories.
Software packages are installed using the Advanced Package Tool (apt) or one of a number of graphical desktop tools and downloaded from the repositories defined within the sources.list file.
In addition to installing and removing software packages, apt may also be used to upgrade those packages with the latest updates. These software upgrades can be performed manually, or configured to automatically update.
In the past, updates to the operating system kernel required a system reboot. With the introduction of Livepatch, the Ubuntu Linux kernel can now be updated dynamically without system interruption.
