Docker 0.6.5 name your containers, link them together, selectively publish ports, and more

Today we’re happy to announce . Don’t be fooled by the version number: this is a significant releas

Today we’re happy to announce . Don’t be fooled by the version number: this is a significant release! Think of it as a preparation for 0.7, which will be even more significant. In addition to numerous bug fixes, this release introduces  A big thank you to (in no particular order) to Paul Nasrat, Tianon Gravi, Edmund Wagner, Travis Cline, Gurjeet Singh, Justin Force, Johan Euphrosine, Ole Reifschneider, Will Rouesnel, Alex Larsson, Greg Thornton, Sven Dowideit, Scott Bessler, Todd Lunter, Vladimir Rutsky, Nicolas Dudebout, Nicolas Dudebout, Roger Peppe, Jerome Petazzoni for your contributions. Not bad for a minor release! (sorry if we forgot anyone).   Two warnings before you upgrade: First, your version of the lxc scripts is unstable and not supported by Docker. Please make sure to install lxc 0.8 or 0.7 before you make the upgrade. Second, in order to improve port redirection we had to introduce 

We did our best to keep the disruption to a minimum, and we hope you’ll agree that the new features are worth it. Please see below for details.   We are happy to announce that we can finally close  ! You can now give memorable names to your containers using the new   flag for  . If no name is specified Docker will automatically generate a name. When you link one container to another you will have to provide the name and alias of the child that you want to link to via  . Enough talk, let’s see some examples! You can run two databases with corresponding names like so: Every command that worked with a container_id can now be used with a name that you specified:   Links allow containers to discover and securely communicate with each other. In 0.6.5 inter-container communication can be disabled with the daemon flag  . With this flag set to false,   cannot access   unless explicitly allowed via a link. This is a huge win for securing your containers. When two containers are linked together Docker creates a parent child relationship between the containers. The parent container will be able to access information via environment variables of the child such as name, exposed ports, ip, and environment variables. When linking two containers Docker will use the exposed ports of the container to create a secure tunnel for the parent to access. If a database container only exposes port 8080 then the linked container will only be allowed to access port 8080 and nothing else if inter-container communication is set to false. When running a WordPress container we need to be able to connect to a database such as MySQL or MariaDB. Using links we can easily swap out the backend database and not have to change our configuration files for the wordpress site. In order to build a wordpress container that works with both databases the container should look for the alias, in our example , when linking to the database. This will allow you to access the database information via consistent environment variables no matter what the name of the container is. Using the two database containers from the naming example we will create a link between them to our wordpress container. To link just add the   flag to  :  or After creating the new container linked into the database container with the alias db you can inspect the environment of the wordpress container and view the ip and port of the database.   $ _PORT_3306_TCP_PORT $ _PORT_3306_TCP_ADDR   The environment variables will be prefixed with the alias you specified on the   flag. For another example we encourage you to read the   example in the Docker documentation. Host integration allows Docker to better integrate with process supervisors like init, upstart, systemd, etc. now automatically attaches to the container’s process and forwards all signals to the container so that process supervisors can detect when the container crashes and correctly restart it. See for details and usage examples. Docker 0.6.5 extends the flag to give you more control over port redirection. Instead of automatically redirecting on all host interfaces, you can specify interfaces to redirect on. Note that this extends the existing syntax without breaking it. For example: You can also choose to  on any host interface, effectively making that port unreachable from the outside. This is very useful in combination with  (see “ ” below), for example to expose an unprotected database port to an application container without publishing it on the public internet. You can do this without a Dockerfile thanks to the new  flag. This release introduces to improve security: First, we are changing the default behavior of  to . This is better for security: ports are private by default, and you can explicitely publish them with the  flag. If you currently rely on exposed ports being published on all host interfaces by default, that will no longer be true in 0.6.5. You can revert to the old behavior by simply adding the appropriate flags. Second, we are deprecating the advanced “  the . This special syntax allowed the Dockerfile to specify in advance that the exposed port should be published on a certain port on all host interfaces. We have found that this hurts separation of concerns between dev and ops, by restricting in advance the system administrator’s ability to configure redirects on the host. The regular “EXPOSE ” syntax is not affected. For example: We apologize for these breaking changes. We did our best to minimize the inconvenience, and we hope you’ll agree that the improvements are worth it!   Happy hacking! —

The Docker team