Project Planning & Execution Flashcards

A project requires containers to be automatically restarted if they crash, but not if stopped manually. Which restart policy should be configured?

Answer: --restart=unless-stopped

The 'unless-stopped' policy restarts crashed containers automatically but respects an explicit manual stop, unlike 'always'.

During project planning, the security team requires all containers to run as a non-root user. How is this enforced in a Dockerfile?

Answer: USER instruction before the CMD or ENTRYPOINT

The USER instruction in a Dockerfile sets the default user for subsequent RUN, CMD, and ENTRYPOINT instructions in the container.

A team plans to use Docker configs (not secrets) to distribute non-sensitive configuration to Swarm services. What is a key difference between Docker configs and Docker secrets?

Answer: Configs are mounted at arbitrary paths; secrets are always mounted at /run/secrets/

Secrets are always mounted under /run/secrets/, while configs can be mounted at any path specified in the service definition.

When planning the execution environment, a developer wants to override the default command of a Docker image at runtime without modifying the Dockerfile. Which approach is correct?

Answer: docker run myimage appends to ENTRYPOINT and replaces CMD

Arguments passed after the image name in 'docker run' replace the default CMD; use --entrypoint to override ENTRYPOINT instead.

A project execution plan requires rolling back a Docker Swarm service to its previous configuration after a failed update. What is the correct command?

Answer: docker service update --rollback

The 'docker service update --rollback' command reverts a service to the configuration it had before the last 'docker service update'.

During project planning, the team wants to inspect the layers of a Docker image to understand what contributed to its size. Which command provides this information?

Answer: docker history

The 'docker history' command shows each layer of an image, including the instruction that created it and the size contribution.

A project plan includes health checks for all services. Where can a HEALTHCHECK instruction be defined so it applies to every container started from an image?

Answer: Directly in the Dockerfile using the HEALTHCHECK instruction

The HEALTHCHECK instruction in a Dockerfile embeds the health check into the image so it runs by default for all containers started from it.