Microsoft Azure CTO Mark Russinovich Microsoft Once upon a time, Microsoft was famous for its resistance to Linux, a free operating system that was developed by a community of enthusiasts and independent vendors.

Microsoft saw Linux as a threat to its growing influence over company data centers — a dominance that made it unloved among the software developer community.

If it wasn't built at Microsoft, the company didn't want any part in it.

But times change. Under new CEO Satya Nadella, Microsoft has embraced Linux and everything it represents, including developer choice. Nadella event went so far as to say "Microsoft loves Linux" at a public company event last year.

"Part of the new Microsoft is being given the permission to meet customers where they're at," Microsoft Azure CTO Mark Russinovich says. "We're no longer bound by an arbitrary rule."

At this week's DockerCon event, Russinovich announced that since this past May, the software giant has been the number one biggest code contributor to Docker, the hot technology that's changing how developers build applications by making it easy to write code once and run it anywhere.

Developers love Docker, which makes it a natural fit for the Microsoft Azure cloud. Azure is locked in an arms race with vendors like Amazon Web Services and Google Cloud Platform to become the friendliest plaform for software developers to build their wares.

But just like Linux, Docker is an open source project, meaning that it has the same kind of active community of developers the world over shepherding its development. In fact, Docker's technology itself is based on a feature that originally came from Linux.

Microsoft CEO Satya Nadella at Microsoft Build 2015 Microsoft Microsoft also this week became a founding member of the Open Container Project, a non-profit to build a container standard housed under none other than the Linux Foundation.

Given the history, it makes it very surprising that Microsoft would give it this kind of love. But for Russinovich, it's all about serving those developers. And to do that, Microsoft wants to contribute and make Docker even better. Part of that is making Docker integrate tightly with the still-formidable Windows Server ecosystem.

"We love Docker because our customers love Docker," Russinovich says. In fact, on stage, Russinovich said that he hasn't had a single customer conversation lately where Docker didn't come up.

In fact, just to show off the commitment Microsoft has to Docker, Russinovich's DockerCon session included a bit where he built and deployed a simple web application, with parts of the application running on Linux and parts running on Microsoft Windows Server.

If that's how developers want it done, Russinovich says, that's where Microsoft will go. There's nothing stopping Microsoft from adopting whatever technologies it takes to get developers on board.

"It's really cool for us to have such a strong relationship [with Docker]," Russinovich says.

Of course, there's another thing that Docker does: It has the potential to make it easier for developers to move their apps from cloud to cloud, since it makes the underlying infrastructure way less important. But Russinovich isn't worried — it just means that Microsoft has to be the best at helping developers work with containers.

"It's not like you can stop it," Russinovich says on the threat of customers moving away.