Deploying services in Swarm in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is Docker Swarm?

Docker Swarm is a tool that lets you manage a group of Docker engines as a single virtual system. It helps you deploy and scale services easily across multiple machines.

beginner

How do you initialize a Docker Swarm on a manager node?

You run the command docker swarm init on the machine you want to be the manager. This sets up the swarm and makes that node the leader.

beginner

What command deploys a new service in Docker Swarm?

Use docker service create followed by options and the image name. For example, docker service create --name myweb nginx deploys an Nginx service named 'myweb'.

beginner

What does the --replicas option do when deploying a service?

It sets how many copies (instances) of the service you want running. For example, --replicas 3 runs three copies of the service.

intermediate

How can you update a running service in Docker Swarm?

Use docker service update with options to change the service. For example, docker service update --replicas 5 myweb changes the number of replicas to 5.

Which command initializes a Docker Swarm manager node?

A docker swarm init

B docker service create

C docker swarm join

D docker container run

The command docker swarm init sets up the current node as a Swarm manager.

What does the command docker service create --replicas 4 nginx do?

A Removes 4 nginx containers

B Creates 1 container running nginx

C Creates 4 containers running nginx as a service in Swarm

D Updates an existing nginx service to 4 replicas

The command creates a new service with 4 replicas of the nginx container.

How do you add a worker node to an existing Docker Swarm?

A docker swarm init

B docker swarm join with the manager's token and IP

C docker service create

D docker container start

Worker nodes join the swarm using docker swarm join with the manager's join token and IP address.

Which command shows the list of services running in a Docker Swarm?

A docker swarm ps

B docker container ls

C docker node ls

D docker service ls

docker service ls lists all services deployed in the swarm.

What happens if you scale a service to zero replicas?

A All service tasks stop running

B One task keeps running

C The service is deleted

D The service restarts automatically

Setting replicas to zero stops all running tasks of that service.

Explain the steps to deploy a new service in Docker Swarm from scratch.

Think about setting up the swarm first, then adding nodes, then deploying the service.

Describe how to update the number of replicas for a running service in Docker Swarm.

Focus on the command that changes service settings without redeploying.