DCA Communication & Stakeholder Relations 4

Question 1

A team lead asks how services in a Docker Swarm discover each other without hardcoding IP addresses. What mechanism enables this?

Accepted Answer

Swarm's built-in DNS-based service discovery

Answer

Docker Swarm provides built-in DNS-based service discovery where service names resolve to virtual IPs automatically.

Question 2

An architect wants to communicate the difference between published ports and exposed ports to developers. Which statement is accurate?

Accepted Answer

EXPOSE documents intent but does not publish; -p actually maps the port to the host

Answer

EXPOSE is metadata documenting which ports the container listens on, while -p actually binds the port to the host network interface.

Question 3

A QA manager asks how to pass environment-specific configuration to containers without rebuilding images. What is the recommended approach?

Accepted Answer

Use -e flags or --env-file to inject environment variables at runtime

Answer

Injecting environment variables at runtime via -e or --env-file keeps images environment-agnostic and reusable.

Question 4

A security stakeholder wants to know how Docker secrets differ from environment variables for sensitive data. What is the key distinction?

Accepted Answer

Secrets are stored encrypted in Swarm Raft and mounted in-memory; env vars are visible in inspect output

Answer

Docker secrets are encrypted at rest in the Swarm Raft store and mounted as tmpfs files, unlike env vars which appear in `docker inspect` output.

Question 5

A release manager asks how to roll back a Docker Swarm service update that introduced errors. Which command should you use?

Accepted Answer

docker service rollback <service>

Answer

`docker service rollback <service>` reverts a service to its previous configuration in Docker Swarm.

DCA - Docker Certified Associate Exam Practice Test