The community of open source software developers behind the Fedora Linux distribution announced this week the release of version 15. The update brings an overhauled desktop user interface and a number of noteworthy architectural improvements under the hood.

Fedora is a community-driven Linux distribution that is sponsored by Red Hat. It is released twice a year on a six-month development cycle and typically ships with the latest cutting-edge Linux software. Fedora is known for riding ahead of the curve and is often the first Linux distro to introduce major new features. It also serves as an incubation space for emerging Red Hat technologies, particularly in areas like virtualization. It lacks the usability and robustness of some other distros, but its unique technical advantages and high commitment to open source ideology are appealing to system administrators, software developers, and software freedom advocates.

The most significant user-facing change in Fedora 15 is the inclusion of GNOME 3.0, a major update of the open source GNOME desktop environment. It brings a completely new desktop shell to Fedora that helps to modernize the user experience. The new shell is built with the Clutter toolkit and requires hardware-accelerated rendering in order to operate. Fedora fortunately does a pretty good job of handling it with open source drivers on many hardware configurations.

The new GNOME brings an enormous number of changes to Fedora that are too numerous to address in this article. Readers who want to know more about the GNOME 3.0 user experience can refer to our full review of the desktop environment. Because Fedora offers the cleanest and most upstream-aligned GNOME 3.0 configuration, we recommend it to readers who want to go hands-on with the desktop environment.

A number of other prominent software applications got rolled over to major new versions in Fedora 15. Firefox 4, which was released in March, is included by default. LibreOffice 3.3, which was released in January, has replaced OpenOffice.org as the standard office suite in Fedora.

There are a number of user-facing technical improvements in Fedora 15. One is a new crash reporting utility that can use remote servers hosted by the Fedora project to do coredump tracing. This allows users to supply highly detailed backtraces in automated crash reports without having to have debug symbols available locally. It will make it easier for upstream developers to troubleshoot software bugs.

The SELinux Troubleshooter, which was originally introduced in Fedora Core 6, has been overhauled for Fedora 15. The new version will hopefully make it easier to detect and resolve conflicts caused by the platform's somewhat temperamental security framework. It's a step forward, but I still prefer to simply disable SELinux when I use Fedora.

Under the hood, the most significant advancement in Fedora 15 is the addition of systemd, a new init system developed by Red Hat's Lennart Poettering, the creator of PulseAudio. It was initially planned for inclusion in Fedora 14, but got pushed back to 15 so that it would have more time to mature.

Because systemd has a number of substantial differences from Upstart and the traditional SysV init, it has some far-reaching implications for the boot process and service management. It uses a dependency system (rather than the event-based approach of Upstart) and on-demand service activation to govern how services are initialized. It has made it easier to further parallelize service initialization at startup, producing some modest improvements to boot performance.

Fedora is the first major distro to adopt systemd as part of the standard installation, but openSUSE and a number of others are planning to do so in the future. In a bid to further advance the reach of systemd and open the door for tighter integration between various layers of the Linux desktop stack, Poettering recently proposed systemd as an external dependency for GNOME.

The proposal proved to be controversial and failed to gain consensus support due to the Linux-centric nature of systemd and lack of widespread distro acceptance. The controversy has generated a lot of curiosity about systemd among Linux enthusiasts. Fedora 15 offers users an opportunity to see how it works in production.

In addition to systemd, another intriguing new feature under the hood is experimental support for the btrfs file system. It's available as an option in the full installer (not the live images), but isn't used by default. Btrfs will eventually replace Ext4 as the default file system in future versions, but it's still not yet ready for serious production use. As such, the feature is offered in Fedora 15 as a preview and isn't really recommended.

The Fedora enthusiasts among our readers tend to be really interested in the distro's virtualization functionality. There are a handful of improvements in this area that are worthy of note. Spice, a technology for network-transparent access to virtualized environments that was first introduced in Fedora 14, is now fully supported through the virt-manager interface in Fedora 15.

Another great new feature that will interest virtualization fans is BoxGrinder, a tool suite for generating virtual appliances in various formats from definition files. It's not as sexy as Novell's intuitive SUSE Studio, but it gets the job done with very little hassle. The definition files use a really simple YAML-based format that is easy to learn and programmatically manipulate.

Fedora 15 is a nice release with some welcome improvements. GNOME users who are looking forward to the next-generation desktop experience will find it particularly pleasing. As usual, there are also plenty of shiny new features under the hood that will satisfy Fedora's more technical audience.

You can download Fedora 15 in a variety of flavors from the project's website. There are installable Live CD images for GNOME, KDE, LXDE, and XFCE users. There is also a hefty DVD installer for users who want lots and lots of packages on disc. Fedora "spins" with specialized configurations are also available, with themes like security, design, and gaming. The release notes can be read online at the Fedora website.