Take a crash course in Ubuntu server administration and learn specific details that set Ubuntu Server apart from other platforms in this chapter from The Official Ubuntu Book.
Ubuntu Server is no different. It depends on the very same archive as the standard Ubuntu distribution, but it installs a distinctive set of default packages. Notably, the set of packages comprising Ubuntu Server is very small. The installer will not install things such as a graphical environment or many user programs by default. But since all the packages for Ubuntu Server come from the same official Ubuntu archive, you can install any package you like later. In theory, there's nothing stopping you from transforming an Ubuntu Server install into a regular Ubuntu desktop installation or vice versa (in practice, this is tricky, and we don't recommend you try it). You can even go from running Kubuntu to running Ubuntu Server. The archive paradigm gives you maximum flexibility.
We've established that Ubuntu Server just provides a different set of default packages than Ubuntu. But what's important about that different set? What makes Ubuntu Server a server platform?
The most significant difference is a nonpreemptible server kernel with an internal kernel timer frequency of 100Hz instead of the desktop default of 1KHz. We'll spare you the OS theory: The idea is to offer some extra performance and throughput for server applications. In addition, the server kernel supports SMP and basic NUMA. SMP, or symmetric multiprocessing, is the code that allows you to use more than one processor in your server, and NUMA is a memory design used in some multiprocessor systems that can dramatically increase multiprocessing performance.
So what else is different in Ubuntu Server? Other than the server kernel and a minimal set of packages, not too much. Though Ubuntu has supported a minimal installation mode for a number of releases, spinning off Ubuntu Server into a proper derivative distribution is still a young effort, and many neat features are planned for the future but aren't available just yet.
Starting with Ubuntu Server 6.06 LTS, known as Dapper Drake, Ubuntu Server offers officially supported packages for the Red Hat Cluster Suite, Red Hat's Global File System (GFS), Oracle's OCFS2 filesystem, and the Linux Virtual Server utilities: keepalived and ipvsadm. Combined with the specialized server kernel, these bits already let you use your Ubuntu Server for some heavy lifting. And there's a great lineup of upcoming features: Among other things, we're hoping to throw in a resource manager for cluster folks, automatically place system configuration files under version control, ship with out-of-the-box support for server farm monitoring and hard drive replication over the network, and provide an integrity checker for installed systems directly on Ubuntu CDs.
Installing Ubuntu Server
So you've downloaded your Ubuntu Server CD from http://releases. ubuntu.com/8.04/ and burned it, eagerly placed it in your CD drive, and rebooted the machine to be greeted by the friendly Ubuntu menu. The first option, Install Ubuntu Server, marks the beginning of a journey toward your very own system administrator cave.
For the most part, server installation is identical to installing a regular Ubuntu machine. This is because Ubuntu takes extra care to ask only the most fundamental questions in the installer, and it turns out those don't differ much between a desktop and a server system. For a quick review of the installation procedure, turn back to Chapter 2. Here, we'll be looking at some of the advanced installer gadgetry that the earlier chapter leaves out and that is particularly geared toward server users.