Creating Images Using a Dockerfile

1 hour
  • 3 Learning Objectives

About this Hands-on Lab

You’ve decided to Dockerize your weather-app. Before you can do this, you’ll need to create an image for it. And you’ll want to keep the image small, so you will create it using a multi-stage build.

Using instructions in a Dockerfile, build the image, then test it by creating a container that uses it.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Create a docker file

Create a docker file:

vi Dockerfile

Dockerfile contents:

FROM node AS source
RUN mkdir -p /node/weather-app
ADD src/ /node/weather-app
WORKDIR /node/weather-app
RUN npm install

FROM node:alpine
ARG APP_VERSION=V1.1
LABEL org.label-schema.version=$APP_VERSION
ENV NODE_ENV="production"
COPY --from=source /node/weather-app /node/weather-app
WORKDIR /node/weather-app
EXPOSE 3000
ENTRYPOINT ["./bin/www"]
Build the image

Use Git commit hash as the image tag:

cd src
git log -1 --pretty=%H
cd ../

Build the image:

sudo docker image build -t linuxacademy/weather-app:[HASH] --build-arg APP_VERSION=2.0 .
Deploy a test container using the image just created

Create the weather-app container:

sudo docker container run -d --name weather-app -p 8080:3000 linuxacademy/weather-app:<HASH>

Additional Resources

In the /home/cloud_user/ directory, you will find the weather-app. Navigate to it. In that directory you will find the source code to the weather-app in src.

Create the Dockerfile

Create a Dockerfile that will use a multi-stage build. The first stage will use node as the base image, and will be called source.

  • Change the directory to weather-app.
  • Create and edit a Dockerfile file.
    • In the file, create a directory for the source code: /node/weather-app.
    • Add the code from src to /node/weather-app on the image.
    • Set /node/weather-app as the working directory.
    • Execute an npm install to install the dependencies.
    • The second stage will use node:alpine as the base image.
    • Create an argument called APP_VERSION that will set the version of the application.
    • Set an environment variable called NODE_ENV and set it to production.
    • Copy /node/weather-app from the source build stage to /node/weather-app.
    • Set /node/weather-app as the working directory.
    • Expose port 3000.
    • Set ./bin/www as the entrypoint.
  • Save the changes to the file.

Build the weather-app image

  • In the src directory, execute git log -1 --pretty=%H to get the commit hash.
  • Use the commit hash as the tag when you execute the image build.
  • Using the build argument, flag set APP_VERSION to 2.0.

Deploy a test container using the image.

  • Create a container called weather-app using the image you just built, and run it as a background process.
    • Publish port 8080 to 3000 on the container.
  • Execute curl localhost:8080 to test the container.

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