Deploying from CI/CD pipeline in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a CI/CD pipeline?

A CI/CD pipeline is a set of automated steps that help developers build, test, and deploy code quickly and safely. It stands for Continuous Integration and Continuous Deployment.

beginner

Why use Docker in a CI/CD pipeline?

Docker packages applications and their dependencies into containers. This makes deployment consistent and easy across different environments in the CI/CD pipeline.

beginner

What is the role of a Dockerfile in deployment?

A Dockerfile is a simple text file with instructions to build a Docker image. It defines what goes inside the container used in deployment.

intermediate

How does a CI/CD pipeline deploy a Docker container?

The pipeline builds a Docker image, pushes it to a registry, then pulls and runs the container on the target server automatically.

beginner

What is a Docker registry?

A Docker registry is a storage and distribution system for Docker images. Examples include Docker Hub and private registries.

What does CI stand for in CI/CD?

A Container Installation

B Continuous Integration

C Code Inspection

D Continuous Improvement

CI means Continuous Integration, which is the practice of merging code changes frequently.

Which file defines how to build a Docker image?

A README.md

B docker-compose.yml

C Dockerfile

D config.json

A Dockerfile contains instructions to build a Docker image.

Where are Docker images stored for deployment?

A Docker registry

B Local folder only

C Source code repository

D Virtual machine

Docker images are stored in a Docker registry to be pulled during deployment.

What is the main benefit of deploying with Docker in CI/CD?

A Consistent environment across stages

B Faster coding speed

C No need for testing

D Manual deployment only

Docker ensures the same environment from build to production, reducing errors.

Which step is NOT part of a typical Docker deployment in CI/CD?

A Building the Docker image

B Pushing image to registry

C Running container on server

D Writing application code manually on server

Writing code manually on the server is not part of automated CI/CD deployment.

Explain the steps involved in deploying a Docker container using a CI/CD pipeline.

Think about how code moves from your computer to the live server.

Describe why Docker helps make deployments more reliable in CI/CD pipelines.

Consider how cooking a recipe exactly the same way every time relates to Docker.

Practice

1. What is the main purpose of using a CI/CD pipeline when deploying Docker applications?

easy

A. To manually update Docker images on each server

B. To write Dockerfiles faster

C. To automate building, testing, and deploying Docker containers

D. To monitor server hardware performance

Solution

1. Step 1: Understand CI/CD pipeline role

   A CI/CD pipeline automates repetitive tasks like building and deploying software.

2. Step 2: Apply to Docker deployment

   For Docker apps, it automates building images, pushing them, and deploying containers.

3. Final Answer:

   To automate building, testing, and deploying Docker containers -> Option C

4. Quick Check:

   Automation = CI/CD pipeline purpose [OK]

Hint: CI/CD pipelines automate repetitive Docker deployment tasks [OK]

Common Mistakes:

• Thinking CI/CD is for manual updates
• Confusing CI/CD with monitoring tools
• Believing CI/CD only speeds up coding

2. Which of the following is the correct Docker command to push an image to a registry in a CI/CD pipeline?

easy

A. docker run myimage:latest

B. docker pull myimage:latest

C. docker build myimage:latest

D. docker push myimage:latest

Solution

1. Step 1: Identify the command to upload images

   The docker push command uploads images to a registry.

2. Step 2: Confirm correct syntax

   docker push myimage:latest correctly pushes the image tagged 'latest'.

3. Final Answer:

   docker push myimage:latest -> Option D

4. Quick Check:

   Push = upload image [OK]

Hint: Push uploads images; pull downloads images [OK]

Common Mistakes:

• Using pull instead of push to upload
• Using build or run commands to push
• Missing image tag in push command

3. Given this snippet in a CI/CD pipeline YAML file:

steps:
  - name: Build image
    run: docker build -t myapp:1.0 .
  - name: Push image
    run: docker push myapp:1.0
  - name: Deploy
    run: kubectl set image deployment/myapp myapp=myapp:1.0

What will happen after this pipeline runs successfully?

medium

A. The Kubernetes deployment will update to use the new Docker image tagged 1.0

B. The Docker image will be deleted from the registry

C. The deployment will roll back to the previous image

D. The Docker image will only be built locally without pushing

Solution

1. Step 1: Analyze build and push steps

   The pipeline builds the image tagged 'myapp:1.0' and pushes it to the registry.

2. Step 2: Analyze deployment step

   The command updates the Kubernetes deployment to use the new image 'myapp:1.0'.

3. Final Answer:

   The Kubernetes deployment will update to use the new Docker image tagged 1.0 -> Option A

4. Quick Check:

   Build + push + deploy = update deployment [OK]

Hint: Build, push, then deploy updates the app [OK]

Common Mistakes:

• Assuming image is only local, not pushed
• Thinking deployment rolls back automatically
• Confusing deployment update with image deletion

4. A CI/CD pipeline fails at the deployment step with the error: kubectl: error: no deployment found. What is the most likely cause?

medium

A. The Docker image failed to build

B. The Kubernetes deployment name is incorrect or missing

C. The Docker push command was missing

D. The pipeline YAML syntax is invalid

Solution

1. Step 1: Understand the error message

   The error says no deployment found, meaning Kubernetes cannot find the named deployment.

2. Step 2: Identify cause in deployment step

   This usually happens if the deployment name in the kubectl set image command is wrong or missing.

3. Final Answer:

   The Kubernetes deployment name is incorrect or missing -> Option B

4. Quick Check:

   No deployment found = wrong deployment name [OK]

Hint: Check deployment name spelling in kubectl command [OK]

Common Mistakes:

• Blaming build or push steps for deployment error
• Ignoring error details about deployment not found
• Assuming YAML syntax error without checking logs

5. You want to deploy a new version of your Docker app automatically only if tests pass in your CI/CD pipeline. Which sequence of steps is best to ensure this?

hard

A. Run tests -> Build Docker image -> Push image -> Deploy to production

B. Build Docker image -> Push image -> Run tests -> Deploy to production

C. Push image -> Run tests -> Build Docker image -> Deploy to production

D. Deploy to production -> Run tests -> Build Docker image -> Push image

Solution

1. Step 1: Understand the logical order for safe deployment

   Tests must run first to verify code correctness before building and deploying.

2. Step 2: Confirm correct step sequence

   After tests pass, build the Docker image, push it to the registry, then deploy to production.

3. Final Answer:

   Run tests -> Build Docker image -> Push image -> Deploy to production -> Option A

4. Quick Check:

   Tests first, then build, push, deploy [OK]

Hint: Always test before building and deploying [OK]

Common Mistakes:

• Building or pushing before tests pass
• Deploying before tests run
• Running tests after deployment