First, just a note about re-installations. With Ubuntu, a circumstance that will require a complete re-installation of your system is very rare; perhaps mechanical failure of the hard disk would be the most common case.

Many common operating systems may require a complete installation to be performed when critical failures take place or for upgrades to new OS versions. Even if a completely new installation isn't required, often the programs you use must be re-installed to operate properly in the new OS.

Under Ubuntu, it is much more likely that your OS can be repaired rather than replaced if things go wrong. Upgrades never require a wholesale installation; you can always upgrade in-place. And the programs are almost always compatible with successive OS releases. If a new program version requires newer supporting software, the Ubuntu packaging system ensures that all the necessary software is automatically identified and installed. The point is, much effort has been put into avoiding the need for re-installation, so think of it as your very last option. The installer is not designed to re-install over an existing system.

Here's a road map for the steps you will take during the installation process.

If you have problems during the installation, it helps to know which packages are involved in which steps. Introducing the leading software actors in this installation drama:

The installer software, debian-installer, is the primary concern of this manual. It detects hardware and loads appropriate drivers, uses dhcp-client to set up the network connection, runs debootstrap to install the base system packages, and runs tasksel to allow you to install certain additional software. Many more actors play smaller parts in this process, but debian-installer has completed its task when you load the new system for the first time.

To tune the system to your needs, tasksel allows you to choose to install various predefined bundles of software like a Web server or a Desktop environment.