Review: Docker 1.0 is ready for prime time
The first production-ready version of the open source Linux container engine irons out networking and other wrinklesFollow @pvenezia
You may note that the size of that image is quite small. This is because Docker builds deltas out from the parent image, storing only the changes per container. Thus, if you have a 300MB parent image, your container and resulting image might be only 50MB in size, if you installed 50MB of additional applications or services within the container.
You can automate the creation of Docker containers with Dockerfiles, which are files that contain specifications for single containers. For instance, you could create a Dockerfile to set up an Ubuntu container with proper networking, run a bevy of commands within the new container, install software, or perform other tasks, then start the container.
Networking in earlier versions of Docker was based on host bridging, but Docker 1.0 includes a new form of networking that allows a container to connect directly to the host Ethernet interfaces. By default, a container will have a loopback and an interface connected to the default internal bridge, but can also be configured for direct access if desired. Naturally, direct access is faster than bridging.
Nevertheless, the bridging method is very useful in many cases and is accomplished by the host automatically creating an internal network adapter and assigning a subnet to it that is unused on the host itself. Then, when new containers attach to this bridge, their addresses are assigned automatically. You can configure a container to attach to a host interface and port when it starts, so a container running Apache may start and connect to TCP port 8080 on the host (or a randomized port), which is then directed to port 80 on the container itself. Through the use of scripting and administrative control, you could start Docker containers anywhere, collect the port they're using, and communicate that to other parts of the application or service stack that need to use the service.
Docker in the real world
In the right hands, Docker has been ready for production for at least a few releases, and the release of v1.0 should result in more eyeballs on the project. The learning curve for Docker should be relatively short for seasoned Linux administrators, but you can easily try it out for yourself at Docker's online demo.
Docker is a very good example of a workable, foundational, back-end infrastructure component that possesses plenty of utility and functionality for Linux admins and architects, but will be lost on those used to point-and-click interfaces. That's not necessarily a bad thing. Docker still has many places to go from here (e.g. image versioning and private registries) and many areas that could use streamlining (e.g. networking). But this 1.0 release is quite enough to get you started.
This article, "Review: Docker 1.0 is ready for prime time," was originally published at InfoWorld.com. Follow the latest developments in application development, cloud computing, virtualization, and open source at InfoWorld.com. For the latest business technology news, follow InfoWorld.com on Twitter.