Learn to run basic commands with Docker and get to an interactive shell.
Let’s run some simple commands in Docker. For this, we’re going to use the Ubuntu Docker image, which will allow us to run most Linux commands.
$ docker run ubuntu:latest echo "Hello from Ubuntu."
Unable to find image 'ubuntu:latest' locally
latest: Pulling from library/ubuntu
...
2508cbcde94b: Pull complete
Digest: sha256:71cd81252a3563a03ad8daee81047b62ab5d892ebbfbf71cf53415f29c130950
Status: Downloaded newer image for ubuntu:latest
Hello from Ubuntu.
Let’s break that down:
docker run is the Docker command to run a container.ubuntu is the name of the Docker image we’re running in our container. This
image comes from Docker Hub.latest is the “tag”, or version of the image that we want to use.echo "Hello from Ubuntu." is the command that we’re running inside the
container.Docker pulls the image for Ubuntu automatically if it isn’t already cached. Then it runs our echo command.
Instead of running echo, we can ask Docker to run /bin/bash inside the
Ubuntu container. This will get us to an interactive shell.
$ docker run -it ubuntu:latest /bin/bash
root@c267f778d237:/#
We are at a bash prompt! The prompt is # rather than $. This is a great way
to know that you’re at a prompt inside the Docker container rather than on your
host machine. (It also indicates that you’re the root user inside the
container - more on that later). Let’s run some simple commands and have a look
around.
root@c267f778d237:/# echo "Hello from a Bash prompt in an Ubuntu container!"
Hello from a Bash prompt in an Ubuntu container!
root@c267f778d237:/# pwd
/
root@c267f778d237:/# ls
bin boot dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var
Feel free to experiment some more inside the container, when you’re done, run
exit to exit Bash and stop the container. Then move on to the next lab.