Docker 1.5 Released
Written by Kay Ewbank   
Monday, 16 February 2015

A new version of Docker has been released with IPv6 support, read-only containers, stats, “named Dockerfiles” and more. 

Docker is the hugely successful open packaging technology that lets you run an app without having to worry about the system it is running on having the necessary dependencies. Your app gets its own operating system environment packaged with it. Another way to think of it is as containers, lightweight virtual environments that sit on top of an operating system instance and let you run an isolated app.

Docker consists of the runtime and packaging tool, Docker Engine, and Docker Hub, a cloud service for sharing applications and automating workflows. Writing about the new version on the Docker blog, the Docker project team says the new version smashes many long-standing, annoying bugs and adds “a few awesome features.”

The IPv6 support means you can now allocate an ipv6 address to each container, and can resolve ipv6 addresses from within a container. You can even use this feature to have containers communicate across multiple hosts. For the few who have IPv6 this is great news. 

The addition of read-only containers means you can now enable a read-only file system for your container, so you can restrict the locations that an application inside a container can write files to. The Docker code maintainers say that by using this capability in combination with volumes, you can make sure containers only persist data where it can be managed in a known location.

Another major improvement is support for stats on resource use. One of the main advantages of Docker is the ability its containers give you to set resource constraints on your applications to make sure that no one application can take over an entire machine. This relies on collection information on resource usage using profiling. Docker 1.5 introduces a new stats API endpoint and CLI command that will stream live CPU, memory, network IO and block IO for your containers.

You can use the new API endpoint to build tools that feed live resource information for your containers into your existing monitoring solutions. The API can also be used to build live dashboards directly.

One addition that has been requested by many users is the ability to specify which Dockerfile to use in a build, rather than relying on the default Dockerfile. This feature has now been added, with the ability to define multiple Dockerfiles in a single project and specify which one to use at build time.

A final improvement is an image specification detailing how Docker currently builds and formats images and their configuration. The blog post says that the hope is that “these details allow contributors to better understand this critical facet of Docker as well as help contribute to future efforts to improve the image format.”

The full release notes give more information and details of the bug fixes.





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Last Updated ( Monday, 16 February 2015 )