Docker Containerization Docker Swarm and Orchestration 5

Question 1

How do you remove a node from a Docker Swarm cluster from a manager node?

Accepted Answer

docker node rm <node-id>

Answer

Running 'docker node rm <node-id>' on a manager removes the specified node from the Swarm cluster; the node must have left the swarm first.

Question 2

What is the purpose of the '--reserve-memory' flag when creating a Swarm service?

Accepted Answer

It reserves a guaranteed minimum amount of memory for each task

Answer

The --reserve-memory flag tells the Swarm scheduler to only place tasks on nodes with at least that much free memory, acting as a soft reservation.

Question 3

When deploying a Docker stack with 'docker stack deploy', which file format is required?

Accepted Answer

Docker Compose file (version 3 or higher)

Answer

Docker stack deploy requires a Compose file in version 3 format, which supports Swarm-specific 'deploy' keys ignored by plain docker-compose.

Question 4

What is the purpose of the 'docker swarm join-token worker' command?

Accepted Answer

Displays the token and command needed to add a new worker node to the Swarm

Answer

Running 'docker swarm join-token worker' on a manager outputs the exact 'docker swarm join' command with the current token needed to add a new worker.

Question 5

Which Swarm feature ensures that a service always maintains its desired number of replicas even if tasks fail?

Accepted Answer

Reconciliation loop

Answer

Swarm's reconciliation loop continuously compares the desired state (replica count) with the observed state and creates replacement tasks when needed.

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Docker Containerization Docker Swarm and Orchestration 5