When containers first appeared in Linux, the natural assumption was that it would be yet another of many technologies that Linux has assimilated.
But then came Docker, a novel use of containers to make apps portable and self-contained. It's set Linux vendors scrambling, both to to rethink the way containers are implemented in Linux and to see how Linux can be reworked around Docker's application-centric model.
Here's how four major enterprise Linux distributions are readying themselves for a Docker-ized future.
Not long after Docker started blowing up, Red Hat began rolling Docker support into Red Hat Enterprise Linux and certifying containerized apps for use on the OS. Since then, Red Hat has drastically ramped up ambitions for RHEL; the company wants nothing less than for RHEL to become a full-blown container host system.
The hard part is doing so without upsetting the existing installed base of RHEL. Thus, Red Hat has elected to create RHEL 7 Atomic Host, which works both as a container host and as a conventional RHEL distribution. But with Fedora 21, Red Hat is delving into more experimental territory to see how, or if, future versions of Red Hat can be made over entirely as a container-based system.
Look no further than CoreOS for an example of how radically Linux can be reworked around containers. Rather than take an existing version of Linux and build Docker management features into it, CoreOS took the opposite approach and rebuilt Linux from the inside out as a lightweight system for running almost nothing but containers. If you all you need is your applications, why not concentrate on that?
CoreOS was also built with an eye toward how an OS could make it easier to manage both fleets of systems and herds of applications, with rolling reboots for the former and cluster self-configuration for the latter all built directly into the OS. Small wonder this radical redesign has given other Linux vendors a lot to think about.
Canonical's Linux distribution has recently been viewed as empowering OpenStack, with some of the work recycled into Ubuntu's support for Docker. Rather than create new Docker-specific tools, the latest version of Ubuntu leverages existing Canonical projects like the Juju orchestration system -- which Canonical also uses for OpenStack -- to manage Docker workloads.
Canonical has also vowed to keep Docker up to date in Ubuntu, which ought to be easier under Ubuntu's twice-a-year release cycle. What's worth watching for is how, or if, Ubuntu will use Docker and containers to push the distribution toward being an infrastructure building block.
Of all the enterprise distributions, Suse ranks as the most conservative in its use of Docker, only recently adding support for it in the form of a technical preview. It's unlikely that Suse wants to be left behind; rather, the company values stability and predictability highly, as reflected in its 10-year support lifetime for Linux editions. To that end, don't expect Suse to perform a radical Docker-powered makeover. Instead, Suse will probably refresh Docker regularly as part of its Modules line of third-party software that needs to be kept current in Suse.