The Fedora Project ships new Fedora Server and Workstation releases at roughly six-month intervals. It then maintains each release for around thirteen months. So Fedora N is supported by the community until one month after the release of Fedora N+2. Since the first Fedora Atomic Host shipped, as part of Fedora 21, the project has maintained separate ostree repositories for both active Fedora releases. For instance, there are currently trees available for Fedora Atomic 25 and Fedora Atomic 24.
Fedora Atomic sets out to be a particularly fast-moving branch of Fedora. It provides releases every two weeks and updates to key Atomic Host components such as Docker and Kubernetes. The release moves more quickly than one might expect from the other releases of Fedora.
Due in part to this faster pace, the Fedora Atomic Working Group has always focused its testing and integration efforts most directly on the latest stable release. The group encourages users of the older release to rebase to the newer tree as soon as possible. Releases older than the current tree are supported only on a
best effort basis. This means the ostree is updated, but there is no organized testing of older releases.
This will change with either the Fedora 26 to 27 or the 27 to 28 upgrade cycle (depending on readiness). The Fedora Atomic Working Group will then collapse Fedora Atomic into a single version. That release will track the latest stable Fedora branch. When a new stable version of Fedora is released, Fedora Atomic users will automatically shift to the new version when they install updates.
Traditional OS upgrades can be disruptive and error-prone. Due to the image-based technologies that Atomic Hosts use for system components (rpm-ostree) and for applications (Linux containers), upgrading an Atomic Host between major releases is like installing updates within a single release. In both scenarios, the system updates are applied by running an rpm-ostree command and rebooting. The release provides rollback to the previous state available in case something goes wrong. Applications running in containers are unaffected by the host upgrade or update.
If you’d like to get involved in the Fedora Atomic Working Group, come talk to us in IRC in #fedora-cloud or #atomic on Freenode, or join the Atomic WG on Pagure.