GitHub Actions with Docker - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the Docker image to use in the GitHub Actions workflow.

Docker

jobs:
  build:
    runs-on: ubuntu-latest
    container:
      image: [1]

Drag options to blanks, or click blank then click option'

Aactions/checkout@v3

Bnode:14

Cubuntu-latest

Ddocker/build-push-action@v3

Attempts:

3 left

💡 Hint

Common Mistakes

Using a GitHub Action name instead of a Docker image.

Using a runner label like 'ubuntu-latest' as image.

The container.image field specifies the Docker image to run the job in. Here, node:14 is a valid Docker image.

2fill in blank

medium

Complete the code to check out the repository in a GitHub Actions workflow step.

Docker

- name: Checkout code
  uses: [1]

Drag options to blanks, or click blank then click option'

Aactions/checkout@v3

Bdocker/build-push-action@v3

Cactions/setup-node@v3

Dactions/upload-artifact@v3

Attempts:

3 left

💡 Hint

Common Mistakes

Using a build or setup action instead of checkout.

Using an upload artifact action here.

The actions/checkout@v3 action checks out your repository code so the workflow can access it.

3fill in blank

hard

Fix the error in the step to build and push a Docker image using the official GitHub Action.

Docker

- name: Build and push Docker image
  uses: docker/build-push-action@v3
  with:
    context: .
    push: [1]

Drag options to blanks, or click blank then click option'

Afalsee

B1

Cyes

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using misspelled boolean values like 'falsee'.

Using strings like 'yes' or numbers like '1'.

The push input expects a boolean value true or false. Here, true enables pushing the image.

4fill in blank

hard

Fill both blanks to set environment variables for Docker Hub username and password in the workflow step.

Docker

- name: Log in to Docker Hub
  uses: docker/login-action@v2
  with:
    username: ${{ secrets.[1] }}
    password: ${{ secrets.[2] }}

Drag options to blanks, or click blank then click option'

ADOCKER_USERNAME

BGITHUB_TOKEN

CDOCKER_PASSWORD

DAWS_SECRET

Attempts:

3 left

💡 Hint

Common Mistakes

Using unrelated secrets like 'GITHUB_TOKEN' or 'AWS_SECRET'.

Mixing up username and password secret names.

You store your Docker Hub username and password as secrets named DOCKER_USERNAME and DOCKER_PASSWORD. These are referenced here.

5fill in blank

hard

Fill all three blanks to build a Docker image with a tag and push it using the GitHub Actions Docker build-push action.

Docker

- name: Build and push Docker image
  uses: docker/build-push-action@v3
  with:
    context: [1]
    push: [2]
    tags: [3]

Drag options to blanks, or click blank then click option'

A.

Btrue

Cmyuser/myapp:latest

Dfalse

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'false' for push when you want to push.

Using wrong context path.

Missing or incorrect image tag.

The context is the build folder, usually .. push must be true to push the image. tags is the image name and tag.

Practice

1. What is the main purpose of using GitHub Actions with Docker in a project?

easy

A. To automate building and testing Docker images on code changes

B. To manually run Docker commands on your local machine

C. To replace Docker with a different container tool

D. To write Dockerfiles without using any commands

Solution

1. Step 1: Understand GitHub Actions role

   GitHub Actions automates tasks like building and testing when code changes happen.

2. Step 2: Connect automation with Docker

   Using GitHub Actions with Docker means automating Docker image builds and tests on events like pushes.

3. Final Answer:

   To automate building and testing Docker images on code changes -> Option A

4. Quick Check:

   Automation with Docker = D [OK]

Hint: GitHub Actions automate tasks triggered by code events [OK]

Common Mistakes:

• Thinking GitHub Actions replace Docker itself
• Confusing manual commands with automation
• Assuming Dockerfiles are written by GitHub Actions

2. Which of the following is the correct syntax to build a Docker image inside a GitHub Actions workflow step?

easy

A. run: docker start -t myimage .

B. run: docker create myimage .

C. run: docker push -t myimage .

D. run: docker build -t myimage .

Solution

1. Step 1: Recall Docker build command

   The command to build an image is 'docker build' with '-t' to tag the image.

2. Step 2: Match with GitHub Actions step syntax

   In GitHub Actions, 'run:' is used to run shell commands, so 'run: docker build -t myimage .' is correct.

3. Final Answer:

   run: docker build -t myimage . -> Option D

4. Quick Check:

   Build image command = C [OK]

Hint: Use 'docker build -t name .' to build images [OK]

Common Mistakes:

• Using 'docker create' instead of 'docker build'
• Confusing 'docker start' with building images
• Using 'docker push' to build images

3. Given this GitHub Actions workflow step:

run: |
  docker build -t test-image .
  docker run --rm test-image echo Hello

What will be the output when this step runs successfully?

medium

A. test-image

B. Hello

C. docker build completed

D. Error: image not found

Solution

1. Step 1: Understand the commands run

   The first command builds an image tagged 'test-image'. The second runs a container from it that prints 'Hello'.

2. Step 2: Identify the output of the run command

   The 'docker run' command runs 'echo Hello' inside the container, so the output is 'Hello'.

3. Final Answer:

   Hello -> Option B

4. Quick Check:

   docker run echo output = Hello [OK]

Hint: Run command output is what container prints [OK]

Common Mistakes:

• Thinking build command outputs 'test-image'
• Expecting build success message as output
• Assuming image not found error without build

4. You have this GitHub Actions step:

run: docker build -t myapp .
run: docker run myapp

The workflow fails with 'Error: Dockerfile not found'. What is the likely cause?

medium

A. The Dockerfile is missing in the repository

B. The two 'run' commands are separate steps and do not share state

C. The image name 'myapp' is invalid

D. The 'docker run' command syntax is incorrect

Solution

1. Step 1: Understand docker build requirement

   The 'docker build .' command requires a Dockerfile in the current directory (repo root after checkout).

2. Step 2: Identify the error cause

   If the Dockerfile is missing from the repository, the build step fails with 'Dockerfile not found' error.

3. Final Answer:

   The Dockerfile is missing in the repository -> Option A

4. Quick Check:

   docker build fails = no Dockerfile [OK]

Hint: Ensure Dockerfile exists in repository root [OK]

Common Mistakes:

• Thinking separate steps prevent image sharing
• Assuming image name 'myapp' is invalid
• Believing 'docker run' syntax causes the error

5. You want to create a GitHub Actions workflow that builds a Docker image only when a push happens to the 'main' branch and then pushes the image to Docker Hub. Which of these YAML snippets correctly sets the trigger and steps?

hard

A. on:
push:
tags:
- main
jobs:
build:
runs-on: ubuntu-latest
steps:
- run: docker build -t myuser/myapp .
- run: docker push myuser/myapp

B. on:
pull_request:
branches:
- main
jobs:
build:
runs-on: ubuntu-latest
steps:
- run: docker build -t myapp .
- run: docker push myapp

C. on:
push:
branches:
- main
jobs:
build:
runs-on: ubuntu-latest
steps:
- uses: actions/checkout@v3
- run: docker build -t myuser/myapp:latest .
- run: echo ${{ secrets.DOCKER_PASSWORD }} | docker login -u ${{ secrets.DOCKER_USERNAME }} --password-stdin
- run: docker push myuser/myapp:latest

D. on:
push:
branches:
- develop
jobs:
build:
runs-on: ubuntu-latest
steps:
- run: docker build -t myuser/myapp .
- run: docker push myuser/myapp

Solution

1. Step 1: Check trigger event and branch

   on: push: branches: - main jobs: build: runs-on: ubuntu-latest steps: - uses: actions/checkout@v3 - run: docker build -t myuser/myapp:latest . - run: echo ${{ secrets.DOCKER_PASSWORD }} | docker login -u ${{ secrets.DOCKER_USERNAME }} --password-stdin - run: docker push myuser/myapp:latest triggers on push to 'main' branch, which matches the requirement.

2. Step 2: Verify build and push steps

   on: push: branches: - main jobs: build: runs-on: ubuntu-latest steps: - uses: actions/checkout@v3 - run: docker build -t myuser/myapp:latest . - run: echo ${{ secrets.DOCKER_PASSWORD }} | docker login -u ${{ secrets.DOCKER_USERNAME }} --password-stdin - run: docker push myuser/myapp:latest includes checkout, build with proper tagging, login using secrets, and push commands correctly.

3. Final Answer:

   The snippet that triggers on push to main, checks out code, logs in with secrets, builds tagged image, and pushes -> Option C

4. Quick Check:

   Push on main + login + build + push = A [OK]

Hint: Use 'on: push: branches: - main' and login before push [OK]

Common Mistakes:

• Using pull_request instead of push event
• Triggering on tags instead of branches
• Pushing without Docker login step