Now that everything is installed, we can test different commands.
The first one is:
docker run hello-world
If everything is correctly installed, Docker will pull image from the Docker registry (Docker Hub), load and run the container.
We get now a Busybox image (a binary file, heavily used in Linux and Unix environment)
docker pull busybox
In case you get a permission denied message, you should use the sudo in front of it
To see all images avaible on your system, use that command:
docker images
Let's run the container based on this image
docker run busybox
... and nothing happens??
In fact, plenty of things are happening. With run command, Docker pull the image, load the container and run a command.
Since we don't give any command, the container runs and then exit.
To see how command runs, let's do this:
docker run busybox echo "Hello from busybox"
The command had been executed but container exited again.
To see running container, use this command:
docker ps
No container is running at the moment. To see those stopped, we can do:
docker ps -a
It's a list of all containers we used until now.
But how to run several command in a container?
With the -it argument
docker run -it busybox sh
A / # appear, where we can type any command just like a standard bash terminal!
Let's test ls or uptime
[!]
If you're aventurous, it's possible to use, inside the container, rm -rf bin. After that, ls or echo won't work anymore.
But don't forget that it must be done inside the container or you'll lose a lot of work or even break your system.
Just type exit to go outside of the container's terminal.
Use that command again
docker run -it busybox sh
and your container will run normally, just like if you haven't done anything to it; because it's a brand new container each time.
More info about the run command:
docker run --help
As a rule of thumb, you can clean up containers once uou're done with them. To do that, run the docker command
docker rm <container_id>
You can see the <container_id> with this command:
docker ps -a
Some characters are required to select and delete the container, you're not forced to write it completely
If you want to erase several containers at once:
docker rm $(docker ps -a -q -f status=exited)
The -q returns only numerical IDs, -f filters outputs on the condition status=exited
In later versions of Docker, that command can be achieved for the same result:
docker container prune