Practical Information

In the following, the installation and setup process of DockerCE and Docker Swarm is described, and at the end, some examples on how to use Docker Services is given.

Installation of Docker

To install DockerCE on a node in the Swarm the following command can be used to set up the local Docker environment:

curl -fsSL https://get.docker.com -o get-docker.sh | sh get-docker.sh

Once the Docker engine has been installed, it is recommended that the user is added to the Docker group so that every Docker command is not run as root. The following command ensures that your user is added to the Docker group:

sudo usermod -aG docker <USERNAME>@student.aau.dk

If the Docker installation is going to be used in a Docker Swarm at AAU, the following changes are needed since the AAU network is running on the default Docker subnet.

For local installations use the following.

nano /etc/docker/daemon.json

and insert the following:

{
  "bip": "10.14.0.1/16",
  "ipv6": false
}

For the Swarm overlay network first create the network manualy with the following command:

docker network create --subnet 10.10.0.0/16 -o com.docker.network.bridge.enable_icc=false -o com.docker.network.bridge.name=docker_gwbridge

Initializing the Swarm

REMEMBER TO CREATE THE NETWORK FIRST On the first master server run the following command:

docker swarm init

Adding a Manager to the Swarm

REMEMBER TO CREATE THE NETWORK FIRST Once the Docker Swarm is initialized used the following command on the first master server to get the join token for the swarm:

docker swarm join-token --manager

The output is copied to the new master server.

Adding a Worker to the Swarm

REMEMBER TO CREATE THE NETWORK FIRST To add a worker to the Swarm first run the following command on one of the managers:

docker swarm join-token worker

The output should be run on the servers intended to be workers in the Swarm.

Now that the Docker Swarm has been created and is ready to serve.

Use the following command to verify the Swarm setup:

docker swarm ls

The output should look like this:

ID	HOSTNAME	STATUS	AVAILABILITY	MANAGER STATUS	ENGINE VERSION
yny9ky6b6zczqrjzxd7sl71k6 *	giraf-master00.srv.aau.dk	Ready	Active	Leader	18.09.3
2n08r588w9p8xazc5cm8r6o9o	giraf-master01.srv.aau.dk	Ready	Active	Reachable	18.09.3
wrr68nqt116tk1rszwvdv1nmk	giraf-node00.srv.aau.dk	Ready	Active		18.09.3
bhh5mitvwzdhzbky1cjne9ffg	giraf-node01.srv.aau.dk	Ready	Active		18.09.3
as7n375y2gwcj5vf4h73h9ron	giraf-node02.srv.aau.dk	Ready	Active		18.09.3
koclcs8nxt0y6qu4ho511la0m	giraf-node03.srv.aau.dk	Ready	Active		18.09.3

Examples of Using a Service

Once the Docker Swarm has been set up, it can be used to serve the different parts of the project. In the following, we will give some examples of how to work with the Swarm.

Example nginx

To create a new service, use the following:

docker service create --name nginx-giraf-proxy --replicas 2 -p 80:80 -p 443:443 nginx:1.15

By running this command, a service with two containers will be stated and the containers will have port 80 and 443 exposed to the internet and can be accessed on the Swarms public IP's. The two containers will be running the nginx version 1.15.

To upgrade the version that a service uses, run the following to downgrade or upgrade the service:

docker service update --image nginx:1.15 nginx-giraf-proxy

To increase the number of containers a service creates, use the following command:

docker service scale nginx-giraf-proxy=5

To verify the service use the following command:

docker service ps nginx-giraf-proxy

The outputs should look like this:

ID	NAME	IMAGE	NODE	DESIRED STATE	CURRENT STATE	ERROR	PORTS
iksklc50ttxt	nginx-giraf-proxy.1	nginx:latest	giraf-master01.srv.aau.dk	Running	Running 29 minutes ago

Note that the ports exposed are not listed in this view since it is served through the service and can be seen then running the following command:

docker service ls

ID	NAME	MODE	REPLICAS	IMAGE	PORTS
k6nuoecmam6m	proxy	replicated	5/5	nginx:latest	:80->80/tcp, :443->443/tcp

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Last update: September 18, 2024