Docker swarm is a tool used to create a cluster of docker hosts. With docker swarm, we can create a high availability and high performance cluster where applications are distributed among the hosts. Docker swarm consists of a manager and worker nodes and operations are performed from the manager. In this guide, we are looking at how to set up Docker swarm cluster on Ubuntu 22.04|20.04.
Step 1: Prepare your nodes.
In my set up, I have one manager node and two worker nodes. On each host, configure hosts file to include all the other nodes.
sudo vim /etc/hostsAdd the following content to the file
192.168.1.10 manager.example.com manager
192.168.1.11 worker-01.example.com worker-01
192.168.1.12 worker-02.example.com worker-02Save the file. Ensure that you can ping all the hosts from each host using hostname and not IP address.
Step 2: Install Docker CE on Ubuntu 22.04|20.04
We are going to install Docker CE on the hosts. To install Docker CE on Ubuntu22.04|20.04, following the following steps:
Install dependency packages with the below command
sudo apt update
sudo apt install apt-transport-https ca-certificates curl software-properties-common lsb-releaseAdd docker key:
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/trusted.gpg.d/docker-archive-keyring.gpgAdd docker repository to your hosts with the following commands:
sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"Update packages
sudo apt updateEnsure that you are going to install from the official Docker repo instead of default Ubuntu repo.
$ apt-cache policy docker-ce
docker-ce:
Installed: (none)
Candidate: 5:20.10.17~3-0~ubuntu-jammy
Version table:
5:20.10.17~3-0~ubuntu-jammy 500
500 https://download.docker.com/linux/ubuntu jammy/stable amd64 Packages
5:20.10.16~3-0~ubuntu-jammy 500
500 https://download.docker.com/linux/ubuntu jammy/stable amd64 Packages
5:20.10.15~3-0~ubuntu-jammy 500
500 https://download.docker.com/linux/ubuntu jammy/stable amd64 Packages
5:20.10.14~3-0~ubuntu-jammy 500
500 https://download.docker.com/linux/ubuntu jammy/stable amd64 Packages
5:20.10.13~3-0~ubuntu-jammy 500
500 https://download.docker.com/linux/ubuntu jammy/stable amd64 PackagesInstall Docker CE on Ubuntu22.04|20.04:
sudo apt install docker-ceAfter installing, Docker daemon should be started. Confirm the status by running the below command:
$ systemctl status docker
● docker.service - Docker Application Container Engine
Loaded: loaded (/lib/systemd/system/docker.service; enabled; vendor preset: enabled)
Active: active (running) since Sat 2020-10-17 16:28:08 EAT; 57s ago
TriggeredBy: ● docker.socket
Docs: https://docs.docker.com
Main PID: 2807 (dockerd)
Tasks: 8
Memory: 37.5M
CGroup: /system.slice/docker.service
└─2807 /usr/bin/dockerd -H fd:// --containerd=/run/containerd/containerd.sockAdd your user to Docker group to avoid typing sudo everytime you run docker commands.
sudo usermod -aG docker ${USER}
newgrp dockerStep 3: Create Docker Swarm Cluster onUbuntu 22.04|20.04
To set up swarm cluster, we first need to initialize Docker Swarm mode on the manager node then add the worker nodes to the cluster.
Get interface IP address
# Get active primary interface name
$ ip address
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp1s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 52:54:00:13:e7:d6 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.10/24 brd 192.168.200.255 scope global dynamic noprefixroute enp1s0
valid_lft 3578sec preferred_lft 3578sec
inet6 fe80::bfeb:53e3:8760:78ee/64 scope link noprefixroute
valid_lft forever preferred_lft forever
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:e8:4e:10:c8 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
valid_lft forever preferred_lft foreverFor me the interface for which Docker manager will advertise on is enp1s0
INT_NAME="enp1s0" #replace accordingly
HOST_IP=$(ip addr show $INT_NAME | grep "inet\b" | awk '{print $2}' | cut -d/ -f1)Confirm IP address is saved correctly:
$ echo $HOST_IP
192.168.1.10Run the below command to initialize Docker swarm node on the manager.
$ sudo docker swarm init --advertise-addr $HOST_IP
Swarm initialized: current node (fsuaqqpihi2eabmmq8gldzhpv) is now a manager.
To add a worker to this swarm, run the following command:
sudo docker swarm join --token SWMTKN-1-018kvdektwa74z8fajb5c1u6jyz6qfk4ood8u4qotw7go9jj0p-cfpnh7omy86xcgoh45vau2kaj 192.168.1.10:2377
To add a manager to this swarm, run 'docker swarm join-token manager' and follow the instructions.Step 4: Join Worker Nodes to the Cluster
We are now going to add the ‘worker-01‘ and worker-02 nodes to the cluster ‘manager’ using the ‘join-token’ from the cluster ‘manager’ node.
Run the command printed in the init command output.
$ sudo docker swarm join --token SWMTKN-1-13xo81gxpb3ttjh5e335pfrmz9fbnliikgfys7u8l4r8k4m575-2gsjwjs3y1i4kgeua2yu840hw 192.168.1.10:2377
This node joined a swarm as a worker.Check if the worker nodes are successfully added to the cluster by running the below command on the manager:
$ sudo docker node ls
ID HOSTNAME STATUS AVAILABILITY MANAGER STATUS ENGINE VERSION
etx5xc5guzftmsqx4naqwvump worker-02 Ready Active 19.03.13
xop4jvrkywz4ldsgwqmfacssc * manager Ready Active Leader 19.03.13
bghrkp7ll1b9lb0ikv8x51gzy worker-01 Ready Active 19.03.13Step 5: Deploy application in the Cluster
Let’s create a service Nginx web server to run on default http port 80, and then expose it to the port 8080 on the host.
$ sudo docker service create --name web-server --publish 8080:80 nginx:1.13-alpine
pq5txw0p9c1qcjrrl2lw3mh5p
overall progress: 1 out of 1 tasks
1/1: running [==================================================>]
verify: Service converged Confirm the created service by running the below command:
$ sudo docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
pq5txw0p9c1q web-server replicated 1/1 nginx:1.13-alpine *:8080->80/tcpStep 6: Replicas and Scaling the service.
We are going to make 3 replicas of the web-server service so that it is accessible on the manager and the two worker nodes.
$ sudo docker service scale web-server=3
web-server scaled to 3
overall progress: 3 out of 3 tasks
1/3: running [==================================================>]
2/3: running [==================================================>]
3/3: running [==================================================>]
verify: Service converged Confirm created service replicas
$ sudo docker service ls
ID NAME MODE REPLICAS IMAGE PORTS
pq5txw0p9c1q web-server replicated 3/3 nginx:1.13-alpine *:8080->80/tcpAccess the service from your browser using all the nodes IPs: http://192.168.1.10:8080, http://192.168.1.11:8080 and http://192.168.1.12:8080 and you should get a nginx welcome page as below:
This has been a step-by-step guide on how to set up Docker Swarm on Ubuntu22.04|20.04. I believe it has been helpful. Check more interesting guides below:
- How to install Kubernetes Cluster on Ubuntu with kubeadm
- How to install MicroK8s Kubernetes Cluster on CentOS 8
- How to run local Kubernetes Cluster in Docker Containers
- Install Docker CE on RHEL 7 Linux
- How to run Docker/ Podman Containers as systemd Service
