Docker tutorial

In this tutorial we will learn the basics of docker and prepare a application for a deployment in cloud.

To start take a Linux machine (preffered Mint or Ubuntu) and install docker:

sudo apt-get install -y docker.io docker-compose

If you want to start quickly skip the rest of the tutorial and run this command:

docker-compose -f config/docker-compose.yml up

Http server (simple example)

We will use the official apache2 image from docker public repository (called Docker Hub).

Note: httpd and apache2 are interchangable names.

We can start the server like this:

docker run -p 80:80 httpd:latest

Open http://localhost in browser and viola!

Now we can will mount the current directory to serve the content of this tutorial over the internet:

docker run -p 80:80 -v "${PWD}:/usr/local/apache2/htdocs/" httpd:latest

The -p option makes the docker port visible from the outside world. By default all docker ports are not exposed.

The -v option binds a local directory to the directory that is served by apache.

The -d option lets us run the container in a "detached mode" (in background).

Mysql server

We will use the official mysql image (w/o writing own Dockerfile).

mysql run -d -e MYSQL_ALLOW_EMPTY_PASSWORD="yes" -p 3306:3306 mysql:5

The -e option lets us pass env variables directly to the container. Here the variable MYSQL_ALLOW_EMPTY_PASSWORD allows us to run the server with empty root password.

Note: 3306 is the default mysql port.

Now we have at least 2 options to connect to the server.

Connect using mysql-client (Option 1)

Now we can connect to the mysql server from our local machine, by using mysql-client for example. Install mysql-client first.

sudo apt-get install mysql-client

And connect:

mysql --host=127.0.0.1 --user=root

We instruct mysql to connect to local server, because the 3306 port is forwarded to the docker container.

Note: Specifying localhost instead of the ip address 127.0.0.1 will make mysql try to connect using the unix socket, which will not work because only the TCP/IP port is exposed.

Open the shell in the docker container (Option 2)

Check the container id via docker ps command, and then open the shell:

docker exec -it <CONTAINER-ID> bash

Now you can connect to mysql server from inside docker container:

mysql # no flags required 

Persist data inside container

The data would not be persisted between subsequent docker container runs. To persist the data we have to use mount docker volume. The volume would be created for us and managed completely by docker. Add this option to docker-run: -v tutorial_mysql_vol:/var/lib/mysql.

mysql run -d -e MYSQL_ALLOW_EMPTY_PASSWORD="yes" -p 3306:3306 -v tutorial_mysql_vol:/var/lib/mysql mysql:5

To list all volumes:

docker volume ls

To remove a volume and start over:

docker volume rm tutorial_mysql_vol

Note: If you use volumes created later by docker-compose remember about the prefix with current dir name. The name of the volume would be: docker-example_tutorial_mysql_vol.

Complete application using docker-compose

Now we run an application composed of 3 docker containers: drupal, mysql, phpmyadmin. The application stack should be specified in docker-compose.yml file.

docker-compose -f config/docker-compose.yml up

To stop application:

docker-compose -f config/docker-compose.yml down

Check http://localhost in the browser.

The -d option runs in detached mode.

The -f option allows us to change the compose file, e.g. -f my-file.yml.

The -p option lets us change the name that will be used as prefix for containers, networks, or volumes.

Complete application using Docker Swarm

Deploy the configuration:

docker swarm init
docker stack deploy -c config/app-stack.yml tutorial

Delete the deploy:

docker stack rm tutorial

List services:

docker service ls

Show logs of a service:

docker service logs tutorial_mysql

Own dockerfile

You can create your own docker image by writing a Dockerfile.

docker build ./debian/ -t tutorial-example
docker run -it tutorial-example

You can find a simple example in ./debian/ directory.

Security remarks

Note: Use this for development only. Do not use it on production!

This tutorial is intended to quickly setup drupal application on LAMP stack for development. At least do this in production setup:

1. Setup proper password for mysql root user.
2. Do not expose mysql port (3306) to the outside world.
3. Secure access to phpmyadmin (or disable it completely).
4. Generate new certificates.