Our first containers

Objectives

At the end of this lesson, you will have:

Seen Docker in action.
Started your first containers.

Hello World

In your Docker environment, just run the following command:

$ docker run busybox echo hello world
hello world

(If your Docker install is brand new, you will also see a few extra lines, corresponding to the download of the busybox image.)

That was our first container!

We used one of the smallest, simplest images available: busybox.
busybox is typically used in embedded systems (phones, routers...)
We ran a single process and echo'ed hello world.

A more useful container

Let's run a more exciting container:

$ docker run -it ubuntu
root@04c0bb0a6c07:/#

This is a brand new container.
It runs a bare-bones, no-frills ubuntu system.
-it is shorthand for -i -t.
- -i tells Docker to connect us to the container's stdin.
- -t tells Docker that we want a pseudo-terminal.

Do something in our container

Try to run figlet in our container.

root@04c0bb0a6c07:/# figlet hello
bash: figlet: command not found

Alright, we need to install it.

An observation

Let's check how many packages are installed here.

root@04c0bb0a6c07:/# dpkg -l | wc -l
189

dpkg -l lists the packages installed in our container
wc -l counts them
If you have a Debian or Ubuntu machine, you can run the same command and compare the results.

Install a package in our container

We want figlet, so let's install it:

root@04c0bb0a6c07:/# apt-get update
...
Fetched 1514 kB in 14s (103 kB/s)
Reading package lists... Done
root@04c0bb0a6c07:/# apt-get install figlet
Reading package lists... Done
...

One minute later, figlet is installed!

root@04c0bb0a6c07:/# figlet hello
 _          _ _       
| |__   ___| | | ___  
| '_ \ / _ \ | |/ _ \ 
| | | |  __/ | | (_) |
|_| |_|\___|_|_|\___/

Exiting our container

Just exit the shell, like you would usually do.

(E.g. with ^D or exit)

root@04c0bb0a6c07:/# exit

Our container is now in a stopped state.
It still exists on disk, but all compute resources have been freed up.

Starting another container

What if we start a new container, and try to run figlet again?

$ docker run -it ubuntu
root@b13c164401fb:/# figlet
bash: figlet: command not found

We started a brand new container.
The basic Ubuntu image was used, and figlet is not here.
We will see in the next chapters how to bake a custom image with figlet.

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