This are my notes about docker and how to run it for my projects. I’m sharing them here for convenience of the teams that I’m working with. Note: This is a live document, expect changes any time.

Docker

Basics

Docker can be seen as a light-weight virtual machine runner. It’s not a true virtual machine, but it is enough to provide virtualized environments for servers and clouds. In that context, being light-weight is an advantage, as it consumes less memory than a virtual machine, and the integration with the host environment is more powerful than that of a virtual machine.

OS Support

Docker comes with Linux. Eventually install it using sudo apt-get intall docker. Docker does not run out-of-the-box on Mac or Windows, but it can be run using third-party tools like boot2docker.

Running Docker

Docker is a command with subcommands to run, similar to git or svn.

To see what docker can do, simply run docker.

Getting, installing and running images

To see what images are available on your system, use docker images In order to see what images are available for download on a specific term, use docker search term. An image can be downloaded and installed using the docker pull command. For example, to download and install a ubuntu container, use docker pull ubuntu. To run the container, use docker run ubuntu. That generated a new LXC container, created a new file system, mounted a read/write layer, allocated network interface etc. whatever is required for running a container. You probably want to run it with a specific command in the container, docker run -it ubuntu bash.

Definition: An image in execution is called container.

To see which docker images available on the system, use docker images. To see the docker containers, use docker ps.

Running a command inside a docker container

Find out the docker container using docker ps. Then run the command like this docker exec container-id command. For example, if your container is postgres:latest with id 343147e64921 and you want to run echo hello world in it, run docker exec 343147e64921 echo hello world.

Persistence

The file system per default is in memory (like ramfs). In order to persist files, use the docker commit command.

History

To view the (commited) history, use docker history imagename.

Log / stdout

To view the stdout of a container, use docker logs.