Following hints earlier in the year, a beta of Red Hat Fedora Linux 21 has finally arrived in three incarnations: Cloud, Server, and Workstation. Fedora 21 also provides the first public glimpse of Project Atomic, Red Hat's initiative to produce a Linux distribution optimized as a Docker container host.
Users who have deployed Fedora in the past as a workstation environment can turn to the appropriately named Fedora 21 Workstation. In addition to updates of all previously included software, the new version features a technology preview of the Wayland display server, an improvement on the X.org display server currently used by Linux distributions. Workstation also includes the Dev Assistant tool to provide developers with a fast way to instantiate project environments.
Fedora 21 Cloud allows the best idea of what the "atomic" in Project Atomic means. It's available in two varieties of images: one for use in conventional cloud environments like OpenStack or Amazon Web Services, and a slimmed-down version optimized as a Docker host. The latter -- the "atomic" incarnation -- doesn't have any more moving parts than is absolutely needed and uses Red Hat project rpm-ostree to keep the system updated without the the restrictions of Fedora's package manager.
The kernel in Cloud also comes in two incarnations depending on its use case. For cloud deployments, a slimmed-down kernel sports a minimum of components; for deployment onto bare metal, Fedora provides another kernel with the full complement of add-ons.
Fedora has always served as a proving ground for cutting-edge features across all aspects of Linux, so Fedora 21 Server includes new functionality aimed at users running application-stack servers. A key new Server feature is the Rolekit tool, which provides admins with "a consistent interface to administrators to install and configure all the packages needed to implement a specific server role." That project is still in its early alpha stages, but over the long term, it will let future users deploy a specific kind of server functionality with a single click -- and with the settings for the role available through an API, not merely as the result of a scripted process.
It's with Cloud, though, that new long-term prospects for Docker with Fedora -- and possibly Red Hat Enterprise Linux -- become clear. Docker originally made it possible to deploy applications on Linux in a way that was highly independent of the platform they ran on, and through projects like CoreOS, this concept is now being applied to the way Linux operates.
The latest Fedora incarnations show Red Hat's first step in that same direction, but so far, it doesn't look anything like a CoreOS clone. Rather, Red Hat is taking a more incremental approach where existing Fedora/RHEL users don't need to learn a new deployment and operations paradigm, and the use of containers is optional rather than mandatory.