LTS releases are arguably much more important for servers than they are for desktops. Desktop users can afford to upgrade their operating system every six months, but most server administrators would be reluctant to run a non-LTS release on a production machine.
On servers, therefore, an LTS release is a particularly big deal. Ubuntu 10.04 effectively marks the first chance for server users to take advantage of new features since the Hardy release two years ago. Many of the innovations discussed below were available, at least partially, in Ibex, Jaunty and Karmic, but it's only now that we're likely to see many of them entering production environments.
What's ChangedSo what exactly does Ubuntu 10.04 Server Edition offer that wasn't present in Ubuntu 8.04? For one, it's more cloud-oriented. This fact becomes evident as soon as the installation CD's boot menu appears, offering a separate installation option for "Ubuntu Enterprise Cloud."
The latest version of Ubuntu Server Edition also offers packages that are much better at auto-configuring themselves than their predecessors. In the past, for example, I used to spend hours fighting with the configuration files for the MTA exim. In Lucid, dpkg was able to set it up almost perfectly out-of-the-box. These improvements were available in Jaunty as well, but I can now take advantage of them without having to use a non-LTS release.
The server edition of Lucid also benefits from numerous upstream advancements. For example, the version of KVM, Linux's native virtualization infrastructure, available in the Ubuntu 10.04 repositories is much more mature and feature-rich than its predecessor from the Hardy days. With support for operations like live migration of virtual machines and better integration into management tools, KVM in Lucid is a much more viable alternative to expensive commercial virtualization solutions.
The vmbuilder utility has also evolved into a much more useful tool for Ubuntu 10.04. It existed in Hardy, but the Lucid version offers more features and works much more reliably, in my experience. The script allows users to roll out completely preconfigured virtual machine images, for a variety of hypervisors and versions of Ubuntu, all in one command. The catch is that the specifications of the virtual machine have to be supported by the hardware and software on which it's built--you can't create an image for a 64-bit virtual machine using a 32-bit kernel, for example. All the same, this is a great tool that has saved me a lot of time.
Room for ImprovementDespite the substantial advances discussed above, Ubuntu Server Edition is far from perfect. One glaring weakness is the text-mode installer, which hasn't really changed at all from Hardy and can be confusing at times. While I'm a big supporter of Ubuntu's commitment to leaving X out of the default software stack for Ubuntu Server in order to keep it as lean as possible, offering a graphical version of the installer for servers wouldn't hurt. Just because the operating system is CLI-only doesn't mean the installer has to be as well.
Tools for automating installations would also be helpful. At a minimum, I would be much happier if the server installer took a tip from its desktop counterpart and asked for all the information it needs at the beginning of the installation process, instead of forcing the user to enter information at different times as the installer progresses. If I wanted to have to sit in front of the screen for an hour answering questions every few minutes, I'd install Windows.
To be fair, I should admit that I am perhaps feeling especially bitter towards the installer because it failed entirely on my employer's IBM BladeCenter hardware. It complained that the installation CD did not exist, despite the fact that the installer had booted from that very same CD. There's already a bug report for this, and the issue can be worked around with a little creativity (and a lot of spare RAM). All the same, it is embarrassing that Ubuntu Server Edition fails so spectacularly on popular enterprise-class server hardware.
I have fewer complaints about Ubuntu 10.04 Server Edition once it is finally installed. One criticism is that it doesn't support kernel-mode setting on my hardware, even though other, older distributions do. KMS would be especially nice in a server environment without X installed.
Otherwise, however, the server version of Lucid works quite well, offering a great wealth of packages for what is probably the most minimalist server environment of all major Linux distributions. If you're looking for a Debian-based server operating system with commercial support available, Ubuntu 10.04 is certainly worthy of your consideration.