Running Containers

Introduction

The quickest way to learn Docker is to run something. You need Docker installed and running.

Your first container

$ docker run hello-world

Docker looks for the hello-world image on your computer, downloads it from Docker Hub if needed, starts a container, prints a short welcome message, and exits.

Run a web server

$ docker run -d -p 8080:80 --name my-web nginx

What each part means:

• -d runs it in the background (detached).
• -p 8080:80 publishes a port: traffic to port 8080 on your computer goes to port 80 inside the container.
• --name my-web gives the container a friendly name.
• nginx is the image: a popular web server.

Now open http://localhost:8080 in your browser. You should see the nginx welcome page.

Manage containers

$ docker ps            # list running containers
$ docker ps -a         # list all containers, including stopped ones
$ docker logs my-web   # see what the container printed
$ docker stop my-web   # stop it
$ docker rm my-web     # remove the stopped container
$ docker images        # list images on your computer

Stopping a container does not delete it. Remove it with docker rm when you are done. Adding --rm to docker run removes the container automatically when it stops.

Run something interactively

$ docker run -it ubuntu bash

-it gives you an interactive terminal inside a fresh Ubuntu container. Type exit to leave. Anything you install in there disappears with the container, which is great for safe experiments.

Clean up

Images and stopped containers use disk space. Remove what you do not need, for example with docker rm and docker rmi image-name.

Try it yourself

Run nginx on port 8080, open it in your browser, read its logs, then stop and remove the container.

Summary

• docker run starts a container from an image, downloading it if needed.
• -d runs in the background, -p publishes a port and --name names it.
• Use ps, logs, stop and rm to manage containers.