DCA Docker Swarm & Orchestration

Question 1

What command initializes a Docker Swarm and makes the current node a manager?

Accepted Answer

docker swarm init

Answer

`docker swarm init` initializes a new Swarm on the current node and designates it as the first manager.

Question 2

Which TCP port does Docker Swarm use by default for manager-to-manager communication (Raft consensus)?

Accepted Answer

2377

Answer

Port 2377 is reserved for Swarm cluster management communications between manager nodes.

Question 3

In Docker Swarm, what is a 'task'?

Accepted Answer

A running container instance that is part of a service

Answer

A task is the atomic scheduling unit in Swarm — it represents a single running container that belongs to a service.

Question 4

What command retrieves the join token needed to add a worker node to an existing Swarm?

Accepted Answer

docker swarm join-token worker

Answer

`docker swarm join-token worker` outputs the full `docker swarm join` command with the token required for a worker to join.

Question 5

What is the key difference between 'replicated' and 'global' service modes in Docker Swarm?

Accepted Answer

Replicated services run a specified number of task copies; global services run exactly one task on every available node

Answer

In replicated mode you define a desired replica count; in global mode, the Swarm schedules exactly one task per available node.

DCA - Docker Certified Associate Exam Practice Test