Our CoreOS Alpha channel is designed to strike a balance between offering early access to new versions of software and serving as the release candidate for the Beta and Stable channels. Due to its release-candidate nature, we must be conservative in upgrading critical system components (e.g. systemd and etcd), but in order to get new technologies (like fleet and flannel) into the hands of users for testing we must occasionally include pre-production versions of these components in Alpha.
rkt will join systemd-nspawn and Docker as container runtimes that are available to CoreOS users. Keep in mind that rkt is still pre-1.0 and that you should not rely on flags or the data in
/var/lib/rkt to work between versions. Specifically, next week v0.4.1 will land in Alpha which is incompatible with images and containers created by previous versions of rkt. Besides the addition of
/usr/bin/rkt to the image, nothing major has changed and no additional daemons will run by default.
We have adopted a regular weekly schedule for Alpha releases, rolling out a new version every Thursday. Every other week we release a Beta, taking the best of the previous two Alpha versions and promoting it bit-for-bit. Similarly, once every four weeks we promote the best of the previous two Beta releases to Stable.
Give it a spin
If you want to spin up a CoreOS Alpha machine and get started, check out the documentation for v0.3.2. We look forward to having you involved in rkt development via the rkt-dev discussion mailing list, GitHub issues, or contributing directly to the project. We have made great progress so far, but there is still much to build!