Building images in CI pipeline in Docker - Mini Project: Build & Apply

Building images in CI pipeline

📖 Scenario: You work in a team that uses Docker containers to package applications. Your team wants to automate building Docker images whenever new code is pushed. This helps deliver updates faster and with fewer errors.

🎯 Goal: Build a simple Docker image using a Dockerfile and automate the build process in a CI pipeline script.

📋 What You'll Learn

Create a Dockerfile with a base image and a simple command

Add a variable for the image tag

Write a command to build the Docker image using the tag variable

Print the Docker build command output

💡 Why This Matters

🌍 Real World

Automating Docker image builds in CI pipelines helps teams deliver software updates quickly and reliably.

💼 Career

Knowing how to build Docker images and automate builds is a key skill for DevOps engineers and developers working with containers.

1

Create a Dockerfile

Create a file named Dockerfile with these exact contents:
FROM alpine:3.18
CMD ["echo", "Hello from Docker image"]

Docker

# Create a Dockerfile with the specified content

Need a hint?

The Dockerfile must start with FROM alpine:3.18 and have a CMD that echoes the exact text.

2

Add an image tag variable

In a shell script file named build.sh, create a variable called IMAGE_TAG and set it to myapp:latest.

Docker

# Create IMAGE_TAG variable
# Your code here

Need a hint?

Use IMAGE_TAG=myapp:latest exactly in your script.

3

Write Docker build command

In the build.sh script, add a command to build the Docker image using the IMAGE_TAG variable and the current directory as context. Use docker build -t $IMAGE_TAG ..

Docker

IMAGE_TAG=myapp:latest

# Add docker build command
# Your code here

Need a hint?

Use the exact command docker build -t $IMAGE_TAG . to build the image.

4

Print build command output

Add a command to the build.sh script to print the message Docker image built with tag: $IMAGE_TAG after the build command.

Docker

IMAGE_TAG=myapp:latest

docker build -t $IMAGE_TAG .

# Print build success message
# Your code here

Need a hint?

Use echo "Docker image built with tag: $IMAGE_TAG" to print the message.