CoreOS has signed up four major backers to its App Container specification in a continued bid to provide the industry with a container standard -- one that's an alternative to Docker Inc.'s de facto standard for containers in the data center.
A standard container specification would allow different vendors to build containers in different ways, while still imposing a shared definition and set of terms and conventions. Those terms and conventions would let different vendors' tools work with spec-compliant containers. In addition, compliant containers would be more likely to be able to run across different data center environments.
It's an uphill battle, given that Docker is already widely used by developers, and has momentum as a de facto standard in the marketplace.
However, enterprise IT shops have been more cautious about adopting Docker than independent developers have. There's still a lot of mindshare and future IT budget to be lost or won when it comes to container adoption.
And each of the four new backers of the CoreOS App Container spec will help in its own way. Here's how:
Google: Google, which launches 2 billion containers a week in its internal operations, agrees that the CoreOS proposed standard is a good one. Google software engineers were the ones who produced the Linux control group code that found its way into the Linux Kernel in 2008 to allow the operating system to manage containers in the first place. A Google endorsement is a Good Housekeeping seal of approval to much of the world, when it comes to container design.
[Want to learn more about how CoreOS sees itself vs. Docker? See Rocket Containers: How CoreOS Plans To Challenge Docker.]
Red Hat: Red Hat doesn't produce its own version of containers, but was an early endorser of the Docker Engine and its ability to format a container in software layers. It also recently made generally available its version of Linux, Atomic Host, to run Docker and other containers.
Red Hat's support gives CoreOS credibility on two fronts. One, Red Hat understood early the significance of containers, and it realizes the value to container portability of a standard industry specification. Two, Red Hat is a direct competitor of the CoreOS host system for running containers. Its nod to App Container means that the industry's largest open source firm is endorsing a competitor's work in formulating the spec. Both amount to a big plus for App Container (dubbed appc for short by CoreOS).
VMware: As the established giant in terms of virtualization, VMware is a candidate to be the manager of both virtual machines and containers in many enterprise data centers. That task will be much easier if there's one specification with which many different types of containers and container tools are built. VMware has more or less ignored the alleged threat that containers pose to the continued growth of virtual machine adoption, and instead partnered early with Docker. Now it's ignoring Docker's wish to be the standard, and partnering early with CoreOS on appc. Smart industry players are making their moves; appc is benefiting.
Apcera: Apcera is a lesser known firm than Docker or even CoreOS. It was founded to manage and automate software deployments. It's assumed many future deployments will be done in containers, so it's significant that Apcera officials have decided CoreOs has come up with the right specification for those containers.
Furthermore, Apcera founder Derek Collison was the principal architect for Cloud Foundry, the most popular open source enterprise development platform. He's "one of the elite thinkers behind Cloud Foundry," said Alex Polvi, CEO of CoreOS, in an interview. Within the ranks of Cloud Foundry developers, there's still a strong sense of being just at the start of what containers will accomplish. Cloud Foundry developers are wary of the Docker bandwagon and have their own container format, Garden, though it has been eating Docker's dust for over a year. Apcera, with its support of appc, also may represent the thinking of a significant percentage of developers inside enterprise IT -- many of them Cloud Foundry or future Cloud Foundry users.
To get the App Container spec accepted, the project's leaders recently put in place governance policies and elected maintainers from outside the ranks of CoreOS. They are Charles Aylward of Twitter, Vincentt Batts of Red Hat, and Tim Hockins of Google.
Rocket, CoreOS's container runtime environment, has been redubbed rkt, Polvi said, and it is an implementation of the App Container spec.
"We are just realizing the potential benefits of a shared standard," said Polvi. If that idea becomes a widely shared perception, Docker itself might feel pressure to follow the appc spec. Polvi claimed it wouldn't be that hard for Docker. The specification recognizes the value of the Docker Build function that layers software in a specified sequence into a container.
Docker, however, doesn't have appc's concept of a pod or set of containers that can share the same resources. It could be added to Docker and bring it a step closer to matching the spec, said Polvi.