Docker: Building a Server with Dockerfile

Setting up a Nginx Webserver with Dockerfile

Let's build a static web server with a Dockerfile. The Dockerfile provides a set of instructions for Docker to run on a container. This lets us automate installing items as if it were a bash script.

Create a new directory and cd into it. Because we're installing Nginx, let's create a default configuration file that we'll use for it.

Create a file called default (the most basic nginx configuration file)

[root@blade02 ~]# mkdir nginx-dockerfile
[root@blade02 ~]# cd nginx-dockerfile/
[root@blade02 nginx-dockerfile]# vi default
[root@blade02 nginx-dockerfile]# cat default 
server {
    root /var/www;
    index index.html index.htm;

    # Make site accessible from http://localhost/
    server_name localhost;

    location / {
        # First attempt to serve request as file, then
        # as directory, then fall back to index.html
        try_files $uri $uri/ /index.html;
    }
}

Now lets create the Docker file;

[root@blade02 nginx-dockerfile]# cat Dockerfile 
FROM ubuntu

RUN echo "deb http://archive.ubuntu.com/ubuntu precise main universe" > /etc/apt/sources.list
RUN apt-get update
RUN apt-get -y install nginx

RUN echo "daemon off;" >> /etc/nginx/nginx.conf
RUN mkdir /etc/nginx/ssl
ADD default /etc/nginx/sites-available/default

EXPOSE 80

CMD ["nginx"]

What's this doing?

• FROM will tell Docker what image (and tag in this case) to base this off of
• RUN will run the given command (as user "root") using sh -c "your-given-command"
• ADD will copy a file from the host machine into the container. This is handy for configuration files or scripts to run, such as a process watcher like supervisord, systemd, upstart, forever (etc)
• EXPOSE will expose a port to the host machine. You can expose multiple ports like so: EXPOSE 80 443 8888
• CMD will run a command (not using sh -c). This is usually your long-running process. In this case, we're simply starting Nginx.

In production, we'd want something watching the nginx process in case it fails

We can now build a new docker image from this Dockerfile

docker build -t nginx-example .