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
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  

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~

Verify from Master node: kubectl get nodes

=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


 * References