Docker Static Site

2.0 Webapps with Docker

Great! So you have now looked at docker run, played with a Docker container and also got the hang of some terminology. Armed with all this knowledge, you are now ready to get to the real stuff — deploying web applications with Docker.

2.1 Run a static website in a container

Note: Code for this section is in this repo in the static-site directory.

Let's start by taking baby-steps. First, we'll use Docker to run a static website in a container. The website is based on an existing image. We'll pull a Docker image from Docker Store, run the container, and see how easy it is to set up a web server.

The image that you are going to use is a single-page website that was already created for this demo and is available on the Docker Store as dockersamples/static-site. You can download and run the image directly in one go using docker run as follows.

$ docker run -d dockersamples/static-site

Note: The current version of this image doesn't run without the -d flag. The -d flag enables detached mode, which detaches the running container from the terminal/shell and returns your prompt after the container starts. We are debugging the problem with this image but for now, use -d even for this first example.

So, what happens when you run this command?

Since the image doesn't exist on your Docker host, the Docker daemon first fetches it from the registry and then runs it as a container.

Now that the server is running, do you see the website? What port is it running on? And more importantly, how do you access the container directly from our host machine?

Actually, you probably won't be able to answer any of these questions yet! ☺ In this case, the client didn't tell the Docker Engine to publish any of the ports, so you need to re-run the docker run command to add this instruction.

Let's re-run the command with some new flags to publish ports and pass your name to the container to customize the message displayed. We'll use the -d option again to run the container in detached mode.

First, stop the container that you have just launched. In order to do this, we need the container ID.

Since we ran the container in detached mode, we don't have to launch another terminal to do this. Run docker ps to view the running containers.

$ docker ps
CONTAINER ID        IMAGE                  COMMAND                  CREATED             STATUS              PORTS               NAMES
a7a0e504ca3e        dockersamples/static-site   "/bin/sh -c 'cd /usr/"   28 seconds ago      Up 26 seconds       80/tcp, 443/tcp     stupefied_mahavira

Check out the CONTAINER ID column. You will need to use this CONTAINER ID value, a long sequence of characters, to identify the container you want to stop, and then to remove it. The example below provides the CONTAINER ID on our system; you should use the value that you see in your terminal.

$ docker stop a7a0e504ca3e
$ docker rm   a7a0e504ca3e

Note: A cool feature is that you do not need to specify the entire CONTAINER ID. You can just specify a few starting characters and if it is unique among all the containers that you have launched, the Docker client will intelligently pick it up.

Now, let's launch a container in detached mode as shown below:

$ docker run --name static-site -e AUTHOR="Your Name" -d -P dockersamples/static-site
e61d12292d69556eabe2a44c16cbd54486b2527e2ce4f95438e504afb7b02810

In the above command:

• -d will create a container with the process detached from our terminal

• -P will publish all the exposed container ports to random ports on the Docker host

• -e is how you pass environment variables to the container

• --name allows you to specify a container name

• AUTHOR is the environment variable name and Your Name is the value that you can pass

Now you can see the ports by running the docker port command.

$ docker port static-site
443/tcp -> 0.0.0.0:32772
80/tcp -> 0.0.0.0:32773

If you are running Docker for Mac, Docker for Windows, or Docker on Linux, you can open http://localhost:[YOUR_PORT_FOR 80/tcp]. For our example this is http://localhost:32773.

If you are using Docker Machine on Mac or Windows, you can find the hostname on the command line using docker-machine as follows (assuming you are using the default machine).

$ docker-machine ip default
192.168.99.100

You can now open http://<YOUR_IPADDRESS>:[YOUR_PORT_FOR 80/tcp] to see your site live! For our example, this is: http://192.168.99.100:32773.

You can also run a second webserver at the same time, specifying a custom host port mapping to the container's webserver.

$ docker run --name static-site-2 -e AUTHOR="Your Name" -d -p 8888:80 dockersamples/static-site

To deploy this on a real server you would just need to install Docker, and run the above docker command(as in this case you can see the AUTHOR is Docker which we passed as an environment variable).

Now that you've seen how to run a webserver inside a Docker container, how do you create your own Docker image? This is the question we'll explore in the next section.

But first, let's stop and remove the containers since you won't be using them anymore.

$ docker stop static-site
$ docker rm static-site

Let's use a shortcut to remove the second site:

$ docker rm -f static-site-2

Run docker ps to make sure the containers are gone.

$ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

2.2 Docker Images

In this section, let's dive deeper into what Docker images are. You will build your own image, use that image to run an application locally, and finally, push some of your own images to Docker Cloud.

Docker images are the basis of containers. In the previous example, you pulled the dockersamples/static-site image from the registry and asked the Docker client to run a container based on that image. To see the list of images that are available locally on your system, run the docker images command.

$ docker images
REPOSITORY             TAG                 IMAGE ID            CREATED             SIZE
dockersamples/static-site   latest              92a386b6e686        2 hours ago        190.5 MB
nginx                  latest              af4b3d7d5401        3 hours ago        190.5 MB
python                 2.7                 1c32174fd534        14 hours ago        676.8 MB
postgres               9.4                 88d845ac7a88        14 hours ago        263.6 MB
containous/traefik     latest              27b4e0c6b2fd        4 days ago          20.75 MB
node                   0.10                42426a5cba5f        6 days ago          633.7 MB
redis                  latest              4f5f397d4b7c        7 days ago          177.5 MB
mongo                  latest              467eb21035a8        7 days ago          309.7 MB
alpine                 3.3                 70c557e50ed6        8 days ago          4.794 MB
java                   7                   21f6ce84e43c        8 days ago          587.7 MB

Above is a list of images that I've pulled from the registry and those I've created myself (we'll shortly see how). You will have a different list of images on your machine. The TAG refers to a particular snapshot of the image and the ID is the corresponding unique identifier for that image.

For simplicity, you can think of an image akin to a git repository - images can be committed with changes and have multiple versions. When you do not provide a specific version number, the client defaults to latest.

For example you could pull a specific version of ubuntu image as follows:

$ docker pull ubuntu:12.04

If you do not specify the version number of the image then, as mentioned, the Docker client will default to a version named latest.

So for example, the docker pull command given below will pull an image named ubuntu:latest:

$ docker pull ubuntu

To get a new Docker image you can either get it from a registry (such as the Docker Store) or create your own. There are hundreds of thousands of images available on Docker Store. You can also search for images directly from the command line using docker search.

An important distinction with regard to images is between base images and child images.

• Base images are images that have no parent images, usually images with an OS like ubuntu, alpine or debian.

• Child images are images that build on base images and add additional functionality.

Another key concept is the idea of official images and user images. (Both of which can be base images or child images.)

• Official images are Docker sanctioned images. Docker, Inc. sponsors a dedicated team that is responsible for reviewing and publishing all Official Repositories content. This team works in collaboration with upstream software maintainers, security experts, and the broader Docker community. These are not prefixed by an organization or user name. In the list of images above, the python, node, alpine and nginx images are official (base) images. To find out more about them, check out the Official Images Documentation.

• User images are images created and shared by users like you. They build on base images and add additional functionality. Typically these are formatted as user/image-name. The user value in the image name is your Docker Store user or organization name.