docker

abstract

Docker is a software platform which builds and runs containers. Containers can simulate other computers with different software installed. Development containers can help increase reproducibility and decrease coupling.

basics

• A host machine is a computer which can run containers.
• A container acts like a simulated computer with its own OS and filesystem.
• An image uses the host's filesystem to store files needed to run a container.
• A Dockerfile is a text file which tells Docker how to build a custom image.
• A volume stores files which can be accessed by one or more containers.
• Host files must be copied or mounted before a container can access them.
• Containers on the same host use networks to communicate with each other.
• The Docker daemon manages containers, images, volumes, and networks.

commands

dependencies

• Docker Engine or
• Docker for Mac or
• Docker for Windows

examples

Build an image named myimage:v2 from a Dockerfile in some/folder:

docker build --tag myimage:v2 some/folder

Run bash interactively in a self-destructing container from the myimage:v2 image:

docker run --rm --interactive --tty myimage:v2 bash

Run the default myimage:v2 command with the current folder mounted read-only as /context:

docker run --volume "$(pwd):/context:ro" myimage:v2

Delete the myimage:v2 image and any containers using it:

docker ps --quiet --filter ancestor="myimage:v2" | xargs docker rm --force
docker image rm myimage:v2 --force

Stop all containers, then delete stopped containers and unused objects:

docker ps --quiet | xargs docker kill
docker system prune --force

faq

Where is the official documentation?

Docker docs

Dockerfile reference

docker run reference

Do containers always run as root?

No. Add a USER in a Dockerfile or call docker run with the --user option.

Can I run a container in a container?