Image naming conventions (registry/image:tag) in Docker - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Docker image naming format

Which part of the Docker image name registry.example.com/myapp/backend:1.2.3 specifies the version of the image?

A 1.2.3

B myapp/backend

C myapp

D registry.example.com

💡 Hint

The version is usually indicated after a colon at the end.

The part after the colon (:1.2.3) is the tag, which commonly represents the version of the image.

💻 Command Output

intermediate

Output of docker pull with full image name

What will be the output status when running docker pull registry.example.com/myapp/frontend:latest if the image exists in the registry?

A Error: image not found

B

latest: Pulling from myapp/frontend
Digest: sha256:abc123...
Status: Downloaded newer image for registry.example.com/myapp/frontend:latest

C Status: Image is up to date for registry.example.com/myapp/frontend:latest

D Permission denied

💡 Hint

Pulling an image shows download progress and digest.

When pulling an image that exists, Docker shows the pulling progress and digest, then confirms the image is downloaded.

❓ Configuration

advanced

Correct image name for private registry

Which of the following is the correct Docker image name to push an image to a private registry at myregistry.local:5000 with repository project/api and tag v5?

A project/api:v5

B myregistry.local/project/api:v5

C myregistry.local:5000/project/api:v5

D myregistry.local:project/api:v5

💡 Hint

Private registries often include port numbers after a colon.

The correct format includes the registry hostname with port, followed by repository and tag: myregistry.local:5000/project/api:v5.

❓ Troubleshoot

advanced

Error caused by invalid image tag format

What error will Docker show if you try to tag an image with an invalid tag containing uppercase letters, like myapp/backend:VersionOne?

A Error response from daemon: invalid reference format

B Tag created successfully

C Error: tag contains invalid characters

D Warning: tag converted to lowercase

💡 Hint

Docker tags must be lowercase and follow specific rules.

Docker enforces tag format rules and will reject tags with uppercase letters, showing 'invalid reference format' error.

✅ Best Practice

expert

Choosing the best tag for continuous deployment

In a continuous deployment pipeline, which tag naming strategy is best to ensure traceability and avoid overwriting images unintentionally?

A Use the 'latest' tag for every build

B Use random strings as tags for each build

C Use timestamps as tags like '20240615-1530'

D Use semantic versioning tags like 'v1.2.3' for each build

💡 Hint

Tags should help identify the exact version deployed.

Semantic versioning tags provide clear version info and help track deployments. 'latest' can be overwritten and cause confusion.