Introduction
Docker is a platform that allows developers to create, deploy, and run applications in containers. Docker Compose simplifies managing multi-container applications by defining and running multiple containers as a single application with dependencies and configurations. Compose plugins extend the functionality of Docker Compose, allowing developers to add new commands, modify behavior, or integrate with external services
Kubernetes is an open-source platform for container orchestration and management that automates deployment, scaling, and management of containerized applications. It is often used in conjunction with Docker to manage containerized applications.
✨ Kubernetes provides a framework for automating deployment, scaling, and operations of application containers across clusters of hosts, while Docker provides a standardized way to package and distribute those containers
👉 I will be installing Docker in 3 CentOS7 Virtual Machines in my VMWare workstation
192.168.1.10 👉 Master
192.168.1.20 👉 Node-1
192.168.1.30 👉 Node-2
Before I begin, I will share official documentations available on installing the docker engine and compose
Installing Docker
In all systems,
yum -y install yum-utils
# Saving the docker repository to install docker from it
yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
Checking docker files
yum list docker-ce --showduplicates | sort -r
👉 This should show us different versions of docker available. I will be proceeding with version 18.x
Installing the Docker Engine
yum -y install docker-ce-18.09.8 docker-ce-cli-18.09.8 containerd.io docker-compose-plugin
Checking the docker version
rpm -qa | grep docker
docker-ce-cli-18.09.8-3.el7.x86_64
docker-compose-plugin-2.6.0-3.el7.x86_64
docker-ce-18.09.8-3.el7.x86_64
Enabling and starting the docker service
systemctl start docker
systemctl enable docker
We can check the Docker version
docker version
👉 Working only from the 'Master' Linux
Installing Docker Compose
curl -SL https://github.com/docker/compose/releases/download/v2.2.3/docker-compose-linux-x86_64 -o /usr/local/bin/docker-compose
ln -s /usr/local/bin/docker-compose /usr/bin/docker-compose
chmod +x /usr/local/bin/docker-compose
docker-compose version
Docker Compose version v2.2.3
Installing Kubernetes
👉 I have VSCode and Kubernetes installed in my Host PC to write manifest files for Kubernetes with ease
✨ From the 'Master' VM
Configuring SWAP memory to be deactivated
sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab
swapoff -a
Creating the daemon.json file
vi /etc/docker/daemon.json
{
"exec-opts": ["native.cgroupdriver=systemd"]
}
Reloading the daemon and restarting docker
systemctl daemon-reload
systemctl restart docker
👉 This will change the Docker cgroup drive
Adding the Kubernetes Local Repository
vi /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64
enabled=1
gpgcheck=0
repo_gpgcheck=0
gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg
https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg
# Installing Kuber
yum install -y kubelet-1.19.16-0.x86_64 kubectl-1.19.16-0.x86_64 kubeadm-1.19.16-0.x86_64
Confirming kubernetes installation
rpm -qa | grep kube
kubelet-1.19.16-0.x86_64
kubectl-1.19.16-0.x86_64
kubernetes-cni-0.8.7-0.x86_64
kubeadm-1.19.16-0.x86_64
Enabling ports used
firewall-cmd --permanent --add-port=80/tcp
firewall-cmd --permanent --add-port=443/tcp
firewall-cmd --permanent --add-port=2376/tcp
firewall-cmd --permanent --add-port=2379/tcp
firewall-cmd --permanent --add-port=2380/tcp
firewall-cmd --permanent --add-port=6443/tcp
firewall-cmd --permanent --add-port=8472/udp
firewall-cmd --permanent --add-port=9099/tcp
firewall-cmd --permanent --add-port=10250/tcp
firewall-cmd --permanent --add-port=10251/tcp
firewall-cmd --permanent --add-port=10252/tcp
firewall-cmd --permanent --add-port=10254/tcp
firewall-cmd --permanent --add-port=10255/tcp
firewall-cmd --permanent --add-port=30000-32767/tcp
firewall-cmd --permanent --add-port=30000-32767/udp
firewall-cmd --permanent --add-masquerade
firewall-cmd --reload
Configuring the Kuber cluster on our Master
kubeadm init --apiserver-advertise-address=192.168.1.10 --pod-network-cidr=10.244.0.0/16
Then you can join any number of worker nodes by running the following on each as root:
kubeadm join 192.168.1.10:6443 --token y20gfe.s5kx71a4nh0gzhsw \
--discovery-token-ca-cert-hash sha256:7c46fa0f4ce64ea4642183250afb3305ca17a89867ed877e2eacdf2a835095b3
👉 The final line says to use the "join" command when adding nodes to the cluster.
👉 I specified the Master Node's IP address with the "apiserver-advertise-address" command and the network area for Pod usage with the "pod-network-cidr" command
Moving the authentication data to use kubectl under root user's Home directory .kube
mkdir -p $HOME/.kube
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
chown $(id -u):$(id -g) $HOME/.kube/config
Installing the Network Plugin to be used in Kuber cluster (Flannel)
curl -O -L https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
👉 As I am using a VM with NAT connection, I needed to add the NIC device name to the flannel.yml file
vi kube-flannel.yml
args:
- --ip-masq
- --kube-subnet-mgr
- --iface=ens32
Now, we just need to apply the flannel plugin
kubectl apply -f kube-flannel.yml
systemctl restart kubelet
✨ From Both Node-1 and Node-2 VMs
👉 Same steps as Master node till firewall settings in both nodes
After firewall settings are done, we will use the join command that we got from the Master node
kubeadm join 192.168.1.10:6443 --token 172vji.r0u77jcmcnccm6no \
--discovery-token-ca-cert-hash sha256:72b9648c647f724ab52471847cb06c47b23097375f2e67633b745fc69db16e8d
👉 This will add both nodes to the Kuber cluster created by the Master
This node has joined the cluster:
* Certificate signing request was sent to apiserver and a response was received.
* The Kubelet was informed of the new secure connection details.
Run 'kubectl get nodes' on the control-plane to see this node join the cluster.
Upon successful joining,
kubectl get nodes
NAME STATUS ROLES AGE VERSION
master Ready master 107m v1.19.16
node-1 Ready <none> 91s v1.19.16
node-2 Ready <none> 48s v1.19.16
We can also check pods
kubectl get pods --all-namespaces
👉 A pod represents a single instance of a running process in the cluster
✍ Today I walked through installing Docker and Kubernetes in Linux systems and joined 2 working nodes to the Master Kuber cluster
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