buildimage.md

Build your own Docker image

We're now going to build a customer docker image using nginx as a base.

Review Dockerfile

From your jumpbox, take a look at the Dockerfile:

cd ~/MTC_ContainerCamp/modules/docker
cat Dockerfile

You'll see:

# Use the nginx docker image as base
FROM nginx

# copy files from the host machine into the image
COPY index.html /usr/share/nginx/html

# inform Docker that the container listens on the specified network port(s) at runtime.
EXPOSE 80

Let's explain each of these sections:

• The FROM line says to use the nginx docker image as the base for your custom image.
• The COPY line copys a file from the local filesystem into the container filesystem. In this case, it is copying the local index.html file into the /user/share/nginx.html directory inside the container.
• The EXPOSE line tells docker that the container will be listening on port 80

Build an image

Now we're going to build our custom image. Run the following command:

 docker build --tag myapp .

Now we can look at the docker images cached on our machine:

docker images

You should see at least 2 images, an image for nginx (pulled down in the prior lab) and a new image for myapp. Now let's run our new app:

docker run -d -p 80:80 --name myapp myapp
docker ps

And now you should be able to hit your app from your browser:

http://[ip address of your jumpbox]

Optional: Customize your container

Edit the file index.html and rebuild your container. (Be sure to stop and remove the old container first: docker stop myapp; docker rm myapp)

To edit the index.html file, run the following command: vim index.html

Move the cursor to the text in the body and type a. This will allow you to add/modify text. Once finished editing, hit escape.
Type :wq then enter to save the file and quit.