Following Red Hat’s acquisition of CoreOS last February, that project—otherwise known as CoreOS Container Linux—is being merged with Red Hat’s Project Atomic to create Fedora CoreOS, for securely running containerized workloads at scale. Don’t let the name deceive you—this is not a return to the Fedora Core days, nor is this a shift in direction for Fedora at large;the project operates in parallel to Fedora Desktop (and related spins) and Fedora Server.
According to the release announcement, “Fedora CoreOS combines the provisioning tools, automatic update model, and philosophy of Container Linux with the packaging technology, OCI support, and SELinux security of Atomic Host.” Likewise, Fedora CoreOS “provisions itself with Ignition, runs containers with Podman and Moby, and updates itself atomically and automatically with rpm-ostree.”
SEE: Deploying containers: Six critical concepts (free PDF) (TechRepublic)
The philosophy behind this idea is that—like the desktop-focused Fedora Silverblue—the underlying OS image is immutable making every installation identical, with apps containerized and keeping their data separate from the host system, in the interest of improving stability and reliability. Immutable OSes have the root filesystem mounted as read-only by default, making it resilient against accidental damage and certain types of attacks.
The OSTree project at the Core of Fedora CoreOS and Silverblue allows for greater flexibility as it makes updates atomic—updating requires nothing more than a restart, and if problems exist with an update, it is trivial to reboot and rollback to last known good image. Likewise, on Silverblue, it is possible to easily switch between branches, with migration back and forth between Rawhide (Fedora’s unstable branch), updates-testing, and stable.
That said, CoreOS is built slightly differently as some limitations exist on the initial preview. Presently, only the testing stream exists, with “next” and “stable” not yet produced. Likewise, x86_64 is the only supported architecture at present and PXE and CD booting is not presently supported.
For more, check out “Fedora 31 to drop 32-bit kernel, retain support for 32-bit programs,” and “How to use a post-install script to simplify Fedora desktop set up” on TechRepublic.