Kubernetes

Source: techrepublic.com, linuxtechi.com

Requirements

3 Ubuntu VMs having:

Same version
Having same resources
LAN Connectivity

Installing dependencies

The first thing you must do is install the necessary dependencies. This will be done on all machines that will join the Kubernetes cluster. The first piece to be install is apt-transport-https (a package that allows using https as well as http in apt repository sources). This can be installed with the following command:

sudo apt-get update && apt-get install -y apt-transport-https

Our next dependency is Docker. Our Kubernetes installation will depend upon this, so install it with:

sudo apt install docker.io

Once that completes, start and enable the Docker service with the commands

sudo systemctl start docker
sudo systemctl enable docker

Disable Swap in all the 3 VMs:

sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab

Or:

sudo sed -i '/ swap / s/^/#/' /etc/fstab

Installing Kubernetes

sudo curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add 

Next add a repository by creating the file /etc/apt/sources.list.d/kubernetes.list and enter the following content:

deb http://apt.kubernetes.io/ kubernetes-xenial main 

Save and close that file. Install Kubernetes with the following commands:

apt-get update
apt-get install -y kubelet kubeadm kubectl kubernetes-cni

Initialize your master

Go to the machine that will serve as the Kubernetes master and issue the command:

sudo su
sudo kubeadm init

Before you join a node, you need to issue the following commands (as a regular user):

exit
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Deploying a pod network

You must deploy a pod network before anything will actually function properly:

kubectl apply -f [podnetwork].yaml'

You can use one of the below Pod Networks:

https://kubernetes.io/docs/concepts/cluster-administration/addons/

Verify Pods, all should be running & only DNS pod should be Pending initially:

aman@ubuntu:~$ kubectl get pods --all-namespaces
NAMESPACE     NAME                             READY     STATUS    RESTARTS   AGE
kube-system   etcd-ubuntu                      1/1       Running   0          3m
kube-system   kube-apiserver-ubuntu            1/1       Running   0          3m
kube-system   kube-controller-manager-ubuntu   1/1       Running   0          3m
kube-system   kube-dns-86f4d74b45-wq49s        0/3       Pending   0          4m    <==
kube-system   kube-proxy-g96ml                 1/1       Running   0          4m
kube-system   kube-scheduler-ubuntu            1/1       Running   0          3m

Flannel

Multiple bugs were encountered when implementing Flannel

Here we will be installing the Flannel pod network:

sudo kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
sudo kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/k8s-manifests/kube-flannel-rbac.yml

Issue the command:

kubectl get pods —all-namespaces

Weave Net

Install the WeaveNet Pod:

export kubever=$(kubectl version | base64 | tr -d '\n')
kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$kubever"

Verification

Verify Installation after a few minutes:

aman@ubuntu:~$ kubectl get pods --all-namespaces
NAMESPACE     NAME                             READY     STATUS    RESTARTS   AGE
kube-system   etcd-ubuntu                      1/1       Running   0          11m
kube-system   kube-apiserver-ubuntu            1/1       Running   0          11m
kube-system   kube-controller-manager-ubuntu   1/1       Running   0          11m
kube-system   kube-dns-86f4d74b45-wq49s        3/3       Running   0          12m    <==
kube-system   kube-proxy-g96ml                 1/1       Running   0          12m
kube-system   kube-scheduler-ubuntu            1/1       Running   0          11m
kube-system   weave-net-pg57l                  2/2       Running   0          6m     <==

Joining a node

With everything in place, you are ready to join the node to the master. To do this, go to the node's terminal and issue the command:

sudo su
kubeadm join --token <TOKEN> <MASTER_IP:6443>

OR what ever is shown in the outputof master after kubeadm init:

kubeadm join 10.1.11.184:6443 --token 0lxezc.game230zg6jpa60g --discovery-token-ca-cert-hash sha256:74b34793d0ty56037c71e4a54e7475901bf627~

Deploying a service

At this point, you are ready to deploy a service on your Kubernetes cluster. To deploy an NGINX service (and expose the service on port 80), run the following commands (from the master):

sudo kubectl run --image=nginx nginx-app --port=80 --env="DOMAIN=cluster"
sudo kubectl expose deployment nginx-app --port=80 --name=nginx-http

Go to your node and issue below command, you should see the service listed:

sudo docker ps -a

Verify

kubectl get pods
kubectl get pods -o wide

Troubleshooting

If the Pod creations fails:

kubectl describe pod nginx-app-56f6bb6776-b7cb5

Reset Everything

sudo kubeadm reset
sudo rm -rf .kube