Developers really love Docker, the container technology that lets them develop an application once and run it anywhere, well on any Linux anyway. And now, Docker has $15 million in fresh Series B cash to build a business around that open source technology. That brings total funding to about $26 million since the company launched, originally as dotCloud, in 2011.

Docker is turning into a genuine hit among developers. The open-source tool, which lets engineers “package” pieces of code into containers that they can easily move from computer to computer, has been downloaded more than 400,000 times. Big companies have started using Docker in production, and top cloud providers have announced support for it. In October the company pivoted to rename itself Docker and focus on that technology.