A beginners' guide to 10 useful docker CLI commands.
Docker is a great tool for building microservices, allowing you to create cloud-based applications and systems. To make the most of it via your terminal, here is a run down of the top 10 Docker commands for your terminal.
- Docker key concepts
Docker key concepts
A container is launched by running an image. An image is an executable package that includes everything needed to run an application – the code, a runtime, libraries, environment variables, and configuration files.
A container is a runtime instance of an image–what the image becomes in memory when executed (that is, an image with state, or a user process). You can see a list of your running containers with the command, docker ps, just as you would in Linux.
Top 10 CLI commands
Lists running containers. Some useful flags include:
-a, -all for all containers (default shows just running) and
—-quiet, -q to list just their ids (useful for when you want to get all the containers).
Most of your images will be created on top of a base image from the Docker Hub registry. Docker Hub contains many pre-built images that you can pull and try without needing to define and configure your own. To download a particular image, or set of images (i.e., a repository), use docker pull.
The docker build command builds Docker images from a Dockerfile and a “context”. A build’s context is the set of files located in the specified PATH or URL. Use the -t flag to label the image, for example docker build -t my_container . with the . at the end signalling to build using the currently directory.
Run a docker container based on an image, you can follow this on with other commands, such as
-it bash to then run bash from within the container.
Use this command to display the logs of a container, you must specify a container and can use flags, such as
--follow to follow the output in the logs of using the program. docker logs
This lists the volumes, which are the preferred mechanism for persisting data generated by and used by Docker containers.
Removes one or more containers, such as
docker rm my_container.
Removes one or more images.
docker rmi my_image
Stops one or more containers.
docker stop my_container stops one container, while
docker stop $(docker ps -a -q) stops all running containers. A more direct way is to use
docker kill my_container, which does not attempt to shut down the process gracefully first.
10. Use them together
For example, to clean up all your docker images and containers:
- kill all running containers with
docker kill $(docker ps -q)
- delete all stopped containers with
docker rm $(docker ps -a -q)
- delete all images with
docker rmi $(docker images -q)
Find out more
There are lots more Docker commands, flags and combinations you can learn about in Docker’s CLI Documentation. Keep trying them out and they should become second nature.
This is just the start though, docker-compose is a tool to define multiple docker containers that work together in an application.