The San Francisco-based company behind the popular open source code project Docker.io is changing its name to Docker, effective on Tuesday. The firm was formerly known as dotCloud.

DotCloud was founded in 2010 to provide a multi-language platform-as-a-service for developers. In doing so, the company came up with the idea of containerized virtual machines, in which sets of virtual machines run in a container under one operating system instead of each virtual machine having its own operating system. This approach saves server memory and speeds up virtual machine operations.

In Java programming, a container is a logical construct that defines a set of resources for use by the virtual machines launched inside it. Sun Microsystems, for example, used "zones" as virtual machines running under one copy of Solaris on a host server. Docker implements a similar approach under Linux, explained Ben Golub, CEO of Docker.

Launched six months ago, the Docker.io project was created from dotCloud's early work. Since then, it has grown popular with developers, reminiscent of Linux, the Apache Web server and MySQL in their early days. Docker has been downloaded 100,000 times, and 200 outside developers have contributed to the Docker project.

[ Want to learn more about how Docker was integrated into OpenStack? See OpenStack Havana Has Amazon-Like Aura. ]

The firm has established a registry of applications that have been placed in Docker containers and that are available for public use. Applications and their dependencies, such as application servers, Web servers or connections to databases, all fit into one container file, which can be downloaded or moved from one cloud location to another. The registry shows 20,000 applications.

At least 13,000 developers have competed online Docker training, and 50 developer meet-ups have taken place in 30 cities on use of Docker, Golub said in an interview.

A driver allowing Docker to be used from inside an OpenStack cloud was included in the recent Havana release of the cloud software, potentially easing the task of migrating from one OpenStack cloud to another. The Docker driver is also integrated in Red Hat's OpenShift platform-as-a-service and Red Hat's distribution of OpenStack in Red Hat Enterprise Linux.

"It was a great validation to be accepted into OpenStack," said Golub, adding that Docker representatives will attend the upcoming OpenStack Summit in Hong Kong, where they will demonstrate how to create Docker containers and move applications between clouds. Docker also plans to provide professional consulting on implementing Docker, as well as technical support, in 2014.

Docker is backed by Benchmark Capital, Trinity Ventures, Yahoo founder Jerry Yang, Y Combinator and other investors.