Docker image as artifact in Jenkins - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to build a Docker image named 'myapp' using the Dockerfile in the current directory.

Jenkins

docker build -t myapp[1] .

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

A:latest

B-f Dockerfile

C--rm

D-p 8080:80

Attempts:

3 left

💡 Hint

Common Mistakes

Using port mapping option -p in build command.

Specifying Dockerfile with -f when default is used.

Using --rm which is for container run, not build.

The -t option tags the image. Adding :latest specifies the tag explicitly.

2fill in blank

medium

Complete the Jenkins pipeline step to push the Docker image 'myapp:latest' to Docker Hub.

Jenkins

sh 'docker push myapp[1]'

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

A:stable

B:1.0

C:dev

D:latest

Attempts:

3 left

💡 Hint

Common Mistakes

Pushing an image tag that was not built.

Omitting the tag and causing push failure.

Using a tag that does not exist locally.

The image tag :latest is the default and commonly used for pushing the most recent image.

3fill in blank

hard

Fix the error in the Jenkins pipeline step that logs in to Docker Hub using environment variables.

Jenkins

sh 'docker login -u [1] -p $DOCKER_PASSWORD'

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

A$USERNAME

BDOCKER_USERNAME

C$DOCKER_USERNAME

Ddocker_user

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the $ before environment variables.

Using incorrect variable names.

Passing plain strings instead of variables.

Environment variables in shell commands need the $ prefix to be expanded.

4fill in blank

hard

Fill both blanks to tag the Docker image 'myapp' with the build number and push it.

Jenkins

sh 'docker tag myapp myapp:[1]'
sh 'docker push myapp:[2]'

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

ABUILD_NUMBER

Blatest

C${BUILD_NUMBER}

D1.0

Attempts:

3 left

💡 Hint

Common Mistakes

Using variable names without ${} in shell commands.

Using different tags for tag and push commands.

Using static tags instead of build number.

Use ${BUILD_NUMBER} to insert the Jenkins build number variable in shell commands.

5fill in blank

hard

Fill all three blanks to create a Docker image, tag it with the build number, and push it in a Jenkins pipeline.

Jenkins

sh 'docker build -t myapp:[1] .'
sh 'docker tag myapp:[2] myrepo/myapp:[3]'
sh 'docker push myrepo/myapp:[3]'

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

Alatest

B${BUILD_NUMBER}

D1.0

Attempts:

3 left

💡 Hint

Common Mistakes

Using different tags in build and push commands.

Omitting ${} around environment variables.

Using static tags instead of dynamic build number.

Use ${BUILD_NUMBER} consistently to tag and push the image with the Jenkins build number.

Practice

1. What is the main reason to save a Docker image as an artifact in Jenkins?

easy

A. To run the image on a different operating system

B. To delete the image after the build

C. To convert the image into a container

D. To reuse the image later without rebuilding it

Solution

1. Step 1: Understand Docker image reuse

   Saving a Docker image as an artifact allows you to reuse it later without rebuilding, saving time and resources.

2. Step 2: Identify Jenkins artifact purpose

   Jenkins artifacts store files from builds for later use or sharing, perfect for Docker images.

3. Final Answer:

   To reuse the image later without rebuilding it -> Option D

4. Quick Check:

   Docker image reuse = To reuse the image later without rebuilding it [OK]

Hint: Artifacts store files to reuse later, like saving your work [OK]

Common Mistakes:

• Thinking artifacts delete images
• Confusing image with container
• Assuming artifacts change OS compatibility

2. Which Jenkins pipeline step correctly archives a saved Docker image file named myimage.tar?

easy

A. archiveArtifacts artifacts: 'myimage.tar'

B. archiveArtifacts file: 'myimage.tar'

C. archiveArtifact artifacts: 'myimage.tar'

D. archiveArtifacts files: 'myimage.tar'

Solution

1. Step 1: Recall Jenkins archiveArtifacts syntax

   The correct syntax uses the parameter name 'artifacts' to specify files to archive.

2. Step 2: Match correct parameter and spelling

   archiveArtifacts artifacts: 'myimage.tar' uses 'archiveArtifacts artifacts: 'myimage.tar'', which is correct syntax.

3. Final Answer:

   archiveArtifacts artifacts: 'myimage.tar' -> Option A

4. Quick Check:

   Correct parameter is 'artifacts' = archiveArtifacts artifacts: 'myimage.tar' [OK]

Hint: Use 'artifacts' parameter exactly in archiveArtifacts step [OK]

Common Mistakes:

• Using 'file' instead of 'artifacts'
• Misspelling 'archiveArtifacts'
• Using singular 'archiveArtifact'

3. Given this Jenkins pipeline snippet:

stage('Save Image') {
  steps {
    sh 'docker save myapp:latest -o myapp.tar'
    archiveArtifacts artifacts: 'myapp.tar'
  }
}

What will Jenkins do after this stage completes?

medium

A. Delete the Docker image myapp:latest

B. Save the Docker image as a file and archive it as a build artifact

C. Run the Docker container from the saved image

D. Build a new Docker image named myapp:latest

Solution

1. Step 1: Analyze docker save command

   The command 'docker save myapp:latest -o myapp.tar' saves the Docker image to a file named myapp.tar.

2. Step 2: Understand archiveArtifacts usage

   The 'archiveArtifacts' step archives the saved file as a Jenkins build artifact for later use.

3. Final Answer:

   Save the Docker image as a file and archive it as a build artifact -> Option B

4. Quick Check:

   docker save + archiveArtifacts = Save the Docker image as a file and archive it as a build artifact [OK]

Hint: docker save creates file; archiveArtifacts stores it [OK]

Common Mistakes:

• Confusing save with build
• Thinking it runs containers
• Assuming image is deleted

4. You wrote this Jenkins pipeline snippet:

sh 'docker save myapp:latest -o myapp.tar'
archiveArtifacts file: 'myapp.tar'

Why does Jenkins fail to archive the Docker image file?

medium

A. Because 'docker save' does not create a file

B. Because the image name is incorrect

C. Because the parameter name should be 'artifacts', not 'file'

D. Because archiveArtifacts cannot archive .tar files

Solution

1. Step 1: Check archiveArtifacts parameter

   The correct parameter to specify files is 'artifacts', not 'file'. Using 'file' causes failure.

2. Step 2: Confirm docker save output

   'docker save' correctly creates the file 'myapp.tar', so the problem is not with the file creation.

3. Final Answer:

   Because the parameter name should be 'artifacts', not 'file' -> Option C

4. Quick Check:

   Parameter must be 'artifacts' = Because the parameter name should be 'artifacts', not 'file' [OK]

Hint: Use 'artifacts' parameter exactly in archiveArtifacts step [OK]

Common Mistakes:

• Using 'file' instead of 'artifacts'
• Assuming docker save fails silently
• Thinking archiveArtifacts rejects .tar files

5. You want to reuse a Docker image saved as appimage.tar from a previous Jenkins build artifact in a new pipeline. Which sequence correctly loads and runs the image?

hard

A. sh 'docker load -i appimage.tar'
sh 'docker run appimage:latest'

B. sh 'docker run -i appimage.tar'
sh 'docker load appimage:latest'

C. sh 'docker save -i appimage.tar'
sh 'docker run appimage:latest'

D. sh 'docker load appimage.tar'
sh 'docker run appimage:latest'

Solution

1. Step 1: Understand docker load syntax

   To load an image from a file, use 'docker load -i filename'. This imports the image into Docker.

2. Step 2: Run the loaded image

   After loading, run the image by its tag, e.g., 'docker run appimage:latest'.

3. Final Answer:

   sh 'docker load -i appimage.tar' sh 'docker run appimage:latest' -> Option A

4. Quick Check:

   Load with '-i', then run by tag = sh 'docker load -i appimage.tar' sh 'docker run appimage:latest' [OK]

Hint: Load with 'docker load -i', then run image by tag [OK]

Common Mistakes:

• Using 'docker run' with file instead of image tag
• Confusing 'docker save' with 'docker load'
• Omitting '-i' option in docker load