Deploying from CI/CD pipeline in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Output of Docker command in CI/CD

You run this command in your CI pipeline to build and tag a Docker image:

docker build -t myapp:latest .

What will be the output if the Dockerfile is missing in the current directory?

Docker

docker build -t myapp:latest .

A Successfully built and tagged myapp:latest

B Build completed but image not tagged

C Warning: No Dockerfile specified, using default

D Error response from daemon: Dockerfile not found

💡 Hint

Think about what Docker needs to build an image.

Docker requires a Dockerfile in the specified directory to build an image. If missing, it returns an error saying Dockerfile not found.

🔀 Workflow

intermediate

Correct order of CI/CD deployment steps

Arrange these steps in the correct order for deploying a Dockerized app from a CI/CD pipeline:

A 3,2,1,4

B 2,3,1,4

C 3,1,2,4

D 1,3,2,4

💡 Hint

Think about building before testing and pushing.

First build the image, then test it, push it to registry, and finally deploy it.

❓ Troubleshoot

advanced

Troubleshooting failed Docker push in CI

In your CI pipeline, the Docker push command fails with:

denied: requested access to the resource is denied

What is the most likely cause?

Docker

docker push myregistry.com/myapp:latest

A You are not logged in to the Docker registry

B The Dockerfile has syntax errors

C The image was not built before push

D The Docker daemon is not running

💡 Hint

Think about permissions and authentication.

The error means the registry denied access, usually because the user is not logged in or lacks permissions.

🧠 Conceptual

advanced

Why use multi-stage builds in CI/CD pipelines?

What is the main benefit of using multi-stage Docker builds in a CI/CD pipeline?

A It automatically deploys the image after build

B It allows running multiple containers simultaneously

C It reduces the final image size by separating build and runtime stages

D It speeds up the Docker daemon startup time

💡 Hint

Think about image size and efficiency.

Multi-stage builds let you copy only necessary artifacts to the final image, making it smaller and more secure.

✅ Best Practice

expert

Secure handling of secrets in CI/CD Docker deployments

Which method is the safest way to handle sensitive environment variables (like passwords) during Docker image deployment in a CI/CD pipeline?

A Pass secrets as plain text arguments during docker build

B Store secrets in the CI/CD platform's secret manager and inject at runtime

C Include secrets in the source code repository in a .env file

D Hardcode secrets in the Dockerfile using ENV instructions

💡 Hint

Think about avoiding exposure of secrets in images or code.

Using the CI/CD platform's secret manager keeps secrets out of code and images, injecting them securely at runtime.

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