Ubuntu Server is a fast, free, no-frills Linux distribution that fills a niche between utilitarian Debian and the GUI-driven and, some would argue, over-featured Novell SUSE and Red Hat Enterprise Linux.
In our business transactions benchmarking tests, Canonical's Ubuntu Server 9.0.4 was nearly as fast as the closest Linux cousin we've reviewed recently, Novell's SUSE Linux Enterprise Server 11.
Ubuntu Server doesn't have a GUI. Instead, at installation, users have the choice of adding services, such as DNS, LAMP (Linux Apache MySQL PHP), mail, OpenSSH, PostgreSQL database, print services, SAMBA and/or TomCat Java services.
Users can also configure the server as a svelte virtual machine or manually install server applications and utilities. The installation choices are offered through a simple 'VGA' (character) graphics menu.
Ubuntu Server also includes a version of Eucalyptus - an open source tool for implementing Linux on public and private clouds. It's compatible with Amazon's Elastic Compute Cloud (EC2), Simple Storage Service (S3) and Elastic Book Store (EBS).
Eucalyptus, based on an open source project at the University of California at Santa Barbara, is comprised of a cloud controller, a cluster controller and node controller.
Together, various nodes (operating instances where the work actually happens) are tied together either in local or disparate server locations, according to the desired computational strength, and the needs of availability of the nodes to do actual work.
Since communication among the components uses SOAP, a commonly understood mechanism in application development, we found building clusters into our own cloud to be pretty simple.