k8s Kubernetes Installation and Cluster Setup

• Kubernetes installation and basic setup

Steps to be followed:

1. Installing Kubernetes
2. Setting up a Kubernetes cluster

Step 1: Installing Kubernetes

• 1.1 To download and add the key to allow kubernetes installation, execute the commands mentioned below:

sudo su
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
sudo echo deb http://apt.kubernetes.io/ kubernetes-xenial main > /etc/apt/sources.list.d/kubernetes.list

• 1.2 Update the apt-get package by executing the command mentioned below:

sudo apt-get update

• 1.3 Install the kubernetes and the tools required to manage it. Run the command mentioned below in the terminal:

sudo apt install docker.io kubectl=1.20.5-00 kubeadm=1.20.5-00 kubelet=1.20.5-00

Step 2: Setting up a Kubernetes cluster

• 2.1 Update the apt-get package by executing the command mentioned below:

sudo apt-get update

• 2.2 To initialize the cluster run the following command on the master node

sudo kubeadm init

• 2.3 To start using your cluster, you need to run the following on master node:

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

• 2.4 You should see a single master node deployed on running the command:

sudo kubectl get nodes

• 2.5 Copy the kubeadm join command that you can see on the screen of your master node

• 2.6 Run the copied kubeadm join command as a root user on the worker node. You can use the terminal only lab as a worker node. Make sure you have Kubernetes installed on the worker node and then run the below command.

kubeadm join 172.31.64.38:6443 --token 425qb8.51rbrxc5h862g202 \
    --discovery-token-ca-cert-hash sha256:a502867d97b05820f186e3ee748afddd9142aae4104aee804d30662148138bae

• 2.7 On the master node, run the following command to install the weavenet plugin in order to create a network:

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

• 2.8 List all the nodes again to check the status of nodes using the command:

kubectl get nodes

Pod creation command

kubectl run nginx --image=nginx

kubectl run httpd --image=httpd

Installation command all in one

curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
sudo echo deb http://apt.kubernetes.io/ kubernetes-xenial main > /etc/apt/sources.list.d/kubernetes.list
sudo apt-get update
sudo apt install docker.io kubectl=1.20.5-00 kubeadm=1.20.5-00 kubelet=1.20.5-00
sudo apt-get update

service docker start
service docker status 

kubeadm init

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

sleep 1

kubeadm join 172.31.64.38:6443 --token 425qb8.51rbrxc5h862g202 --discovery-token-ca-cert-hash sha256:a502867d97b05820f186e3ee748afddd9142aae4104aee804d30662148138bae

kubectl get pods -n kube-system

Creating network

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

kubectl commands

kubectl get namespace

kubeadm token list
kubectl get namespaces

kubectl get replicationcontroller,services
kubectl get pods -n kube-public
kubectl get pods -n kube-system
kubectl get pods --all-namespaces

kubectl run nginx --image=nginx
kubectl get pods --all-namespaces

kubectl get pods
kubectl get pods -o wide
kubectl describe pod nginx
kubectl get pods
kubectl run nginx --image=httpd
kubectl run httpd --image=httpd
kubectl get pods

service docker status
sudo kubectl get nodes

Pod Creation in Kubernetes

• Steps to be followed:

1. Creating multi-container pods
2. Creating a single container pod

Step 1: Creating multi-container pods

• 1.1 On the master node, create a new file named sample.yaml:

sudo su
vi sample.yaml
1.2	Add the following code in the multi-container.yaml file:
https://github.com/manikcloud/k8s/blob/main/pods/multi-container.yaml

• 1.3 Use the following command to create the multi-container pod:

kubectl create -f sample.yaml

Step 2: Creating a single container pod

• 2.1 On the master node, create a single container pod with a tomcat image using the following command:

kubectl run tomcat --image=tomcat:8.0

• 2.2 Check all the running pods

kubectl get pods

• 2.3 To check why exactly a pod is in the pending state, run the command -- kubectl describe pods <pod_name>
• To check why multi-container pod is pending,use the command

kubectl describe pods multi-container

2.4 To remove the taint from the node run the following commands:

kubectl get nodes

• Copy the node name and use it in the below command
• kubectl taint nodes node-role.kubernetes.io/master-

Here for example we use the command given below

kubectl taint nodes  ip-172-31-17-206 node-role.kubernetes.io/master-

-- 2.5 Now check the pod status. The pods should be in the running state.

sudo kubectl get pods 

Dashboard Creation in Kubernetes

kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.5.1/aio/deploy/recommended.yaml

kubectl proxy

http://localhost:8001/api/v1/namespaces/kubernetes-dashboard/services/https:kubernetes-dashboard:/proxy/

kubectl -n kube-system describe secret $(kubectl -n kube-system get secret | awk '/^deployment-controller-token-/{print $1}') | awk '$1=="token:"{print $2}'

kubectl -n kube-system describe secret $(
  kubectl -n kube-system get secret | \
  awk '/^deployment-controller-token-/{print $1}'
) | \
awk '$1=="token:"{print $2}'

After executing the above commands, there are 4 distinct commands and they get called in this order:

• Line 1 - This is the second command from @silverfox's Token section.
• Line 2 - This is the first command from @silverfox's Token section.
• Line 3 - Print only the first field of the line beginning with deployment-controller-token- (which is the pod name)
• Line 5 - Print only the second field of the line whose first field is "token:"

ReplicaSet commands in K8S

kubectl apply -f ReplicaSet/ReplicaSet.yaml 
kubectl get pods
kubectl get replicaset 
kubectl delete pod sl-replicaset-hnd76
kubectl descr
kubectl apply -f pods/pod-def.yaml 
kubectl get pods
kubectl apply -f pods/pod-def.yaml 
kubectl get pods
kubectl get replicaset sl-replicaset
kubectl edit replicaset sl-replicaset
kubectl get replicaset sl-replicaset
kubectl scale replicaset sl-replicaset --replicas=2
kubectl get replicaset sl-replicaset
 
kubectl get replicaset sl-replicaset

Deployment commands in K8S

kubectl create -f deployment/deployment.yaml 
kubectl get pods -o wide

kubectl get deployment
kubectl get deployment -o wide
kubectl describe deployment
kubectl create -f deployment/deployment.yaml 
kubectl get pods -o wide 
kubectl rollout history deployment/web-app-deployment 
kubectl delete deployment web-app-deployment
kubectl get pods -o wide 
kubectl create -f deployment/deployment.yaml  --record
kubectl rollout history deployment/web-app-deployment 
kubectl edit deployment web-app-deployment  --record
kubectl rollout history deployment/web-app-deployment 
kubectl rollout status deployment/web-app-deployment 
kubectl get pods -o wide 
kubectl describe deployment web-app-deployment 
kubectl rollout status deployment/web-app-deployment 
kubectl set image deployment web-app-deployment blue=varunmanik/httpd:v1-blue --record
kubectl get pods -o wide
kubectl rollout history deployment web-app-deployment 

scaling commands in K8S

kubectl scale deployment web-app-deployment --replicas=6

Roll Out

kubectl rollout undo deployment/web-app-deployment --to-revision=3
kubectl rollout history deployment web-app-deployment 

Docker testing in you K8S setup

docker build -t varunmanik/httpd:green .
docker run -itd -p 9000:80 varunmanik/httpd:green
docker build -t varunmanik/httpd:blue .
docker run -itd -p 9001:80 varunmanik/httpd:blue
kubectl describe pod green-app | grep -i "IP:"

Services commands in K8S

kubectl create -f services/service-def.yaml 
kubectl describe svc web-app-service
kubectl get svc,pods -o wide
kubectl delete service web-app-service
kubectl get svc,pods -o wide
kubectl scale   deployment/blue-green-deployment --replicas=1
kubectl get svc,pods -o wide
kubectl get svc,pods,deployment -o wide

Cleanup the entire setup

• Run this command to cleanup

sh installation/cleanup.sh

• OR copy and paste below commands one by one.

docker ps 
kubeadm reset -f
rm -rf /etc/cni /etc/kubernetes /var/lib/dockershim /var/lib/etcd /var/lib/kubelet /var/run/kubernetes ~/.kube/*
v
apt remove -y kubeadm kubectl kubelet kubernetes-cni
sudo apt-get purge kubeadm kubectl kubelet kubernetes-cni kube* 
sudo apt-get autoremove
sudo rm -rf ~/.kube
docker ps
system restart docker 
systemctl restart docker 

Check your history from below command

history | cut -c 8- > history.txt

References

1. https://kubernetes.io/
2. https://kubernetes.io/docs/setup/production-environment/tools/kubeadm/create-cluster-kubeadm/
3. https://kubernetes.io/docs/concepts/workloads/pods/
4. https://etcd.io/
5. https://kubernetes.io/docs/reference/kubectl/
6. https://kubernetes.io/docs/tasks/access-application-cluster/web-ui-dashboard/