A lot can change in six months — including the comfort of a $40 million funding cushion, apparently.

Docker Inc. raised that much with a C round in September. But the startup needs even more, so today, it's announcing a $95 million Series D round.

Yes, already. Interest in open source Linux containers is still exploding, with Docker containers as the catalyst. Docker Inc. claims that thousands of enterprises use Docker for deploying applications. The company estimates its user base is in the millions.

The money will go toward helping Docker Inc. keep up with this expanding universe. After launching Docker technology publicly two years ago and changing the company's name from dotCloud Inc., Docker Inc. promised commercial offerings such as managed services and enterprise-grade registries and support.

Some of that has started to emerge. October saw the launch of the Docker Enterprise Hub, for instance. But it seems likely that the popularity of containers is pushing Docker Inc. to step up its timeline for more services. The company also wants to devote more resources to its partnerships with Amazon Web Services, IBM, and Microsoft.

Docker Inc. happens to be on the acquisition trail as well, although the nature and newness of its work mean that the startups it buys aren't exactly pricey. Typical of Docker Inc.'s shopping list are eight-person Koality, which was the acquisition behind Docker Enterprise Hub, and SocketPlane, a networking startup that had existed for mere months before being acquired.

Finally, you can't help wonder if $95 million is meant to keep Docker out of the hands of larger IT players that might want to acquire it. It might also be intended to sustain Docker up to an IPO. (That's a guess, but Illumio, which announced a $100 million funding round today, is talking out loud about wanting to go public.)

New investors joining the Docker Inc. fold include Insight Venture Partners, which led the round, and Coatue, Goldman Sachs, and Northern Trust. Other contributors includes prior investors Benchmark, Greylock Partners, Sequoia Capital, Trinity Ventures and AME Cloud Ventures (Yahoo co-founder Jerry Yang's firm).