Ubuntu 8.04 alpha 4 was officially released today and is now available for testing. This alpha offers an early look at some of the features that will be included in the final 8.04 release, which is scheduled for April. Codenamed Hardy Heron, Ubuntu 8.04 will be the second long-term support (LTS) release, which means that it will be supported on the desktop for three years and on the server for five years.

We tested alpha 4 ourselves, and we are very impressed with some of the hot new features. Ubuntu 8.04 is the first version to include PulseAudio, an open-source sound server that offers sophisticated mixing capabilities and network transparency. PulseAudio offers several potential improvements to the desktop user experience, including support for independently controlling the volume of individual applications, transferring audio streams between devices, and outputting a stream on multiple devices at the same time. PulseAudio is installed by default in alpha 4 but hasn't been fully integrated into the system yet. During this stage of the transition, volume controls are inaccessible, so there isn't much testing that one can do with it right now.

Another very significant architectural change in Ubuntu 8.04 is the inclusion of GIO and GVFS, a new I/O abstraction layer and virtual file system mechanism. GVFS replaces the antiquated GnomeVFS library and uses the D-Bus interprocess communication protocol to coordinate between various daemons that handle mounting and file operations. These components have been integrated into Nautilus, the GNOME file manager. There are still some bugs that need to be resolved and not all of the previously supported network protocols are working with it yet, but it already provides a few new features that are visible to the user. In particular, Nautilus will now queue up long file transfer operations and display them in a single window rather than spawning a separate window for each file transfer operation.





File transfer queue in Nautilus using GVFS

Ubuntu 8.04 also adds PolicyKit, a new framework for secure privilege escalation. The Ubuntu developers aim to completely eliminate the anachronistic gksudo component by bringing pervasive PolicyKit integration to every corner of the system. Unlike gksudo, which grants elevated root privileges to an entire program, PolicyKit makes it possible to isolate privileged actions and make them accessible to programs through a D-Bus interface. This approach provides a much higher level of security and also gives administrators more flexible control over what operations are accessible to individual users. PolicyKit still uses password prompts like gksudo, so the difference to end users will be minimal. In some system configuration utilities, like the network settings tool, there are now Unlock buttons which, when clicked, will present the user with a password prompt before making privileged elements of the user interface accessible. PolicyKit also includes an authorization management tool that provides an overview of all the privileged operations exposed through PolicyKit and allows administrators to configure permissions for each individual operation.





The PolicyKit authorization manager tool

There are a handful of other subtle improvements in Ubuntu 8.04 that are already present in this alpha release. The panel clock applet, for instance, has been improved to include support for displaying weather information and times for multiple locations in its expanded view. Ubuntu 8.04 also replaces the unmaintained GNOME BitTorrent client with Transmission, a cross-platform BitTorrent client that offers a nice GTK interface for Linux. Also new is the Brasero CD burning program and a much-improved System Monitor utility with a rich Cairo-based visual display.





The new GNOME System Monitor tool





The new world clock feature

Although many of the significant architectural features like PulseAudio and GIO are still in transitional stages and aren't fully functional yet, Ubuntu 8.04 alpha 4 is still very impressive. I'm a big fan of D-Bus, and I'm very pleased to see it being adopted throughout the entire desktop stack in core components. I'm also very impressed with the relative completeness of PolicyKit integration, and I'm looking forward to the promised performance improvements and support for pausing file transfers that we should get when GIO is more mature. Many of the major pieces are falling into their proper places for Hardy Heron, but there are still some things that haven't landed yet. One of the significant features planned for 8.04,for instance, is a complete visual refresh, with totally new artwork and new GTK theme. The new artwork hasn't begun showing up yet.

It should be noted that this is a prerelease and isn't intended for use in production environments. Some parts are particularly fragile, and the Ubuntu developers are encouraging users to refrain from using Nautilus to operate on valuable files until GVFS stabilizes a bit. Users who want to test Ubuntu 8.04 alpha 4 can download an installation ISO and give it a try. ISOs are also available for Kubuntu, Edubuntu, Ubuntu JeOS, Xubuntu, and Gobuntu.