K8s Essentials

Kubenetes Essentials

Installing Docker.

curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -

sudo add-apt-repository \
   "deb [arch=amd64] https://download.docker.com/linux/ubuntu \
   $(lsb_release -cs) \
   stable"

sudo apt-get update

sudo apt-get install -y docker-ce=18.06.1~ce~3-0~ubuntu

sudo apt-mark hold docker-ce

You can verify that docker is working by running this command:

sudo docker version

Installing kubelet, kubeadm, and kubectl.

Note: There are some issues being reported when installing version 1.12.2-00 from the Kubernetes ubuntu repositories. You can work around this by using version 1.12.7-00 for kubelet, kubeadm, and kubectl.

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

cat << EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF

sudo apt-get update

sudo apt-get install -y kubelet=1.12.7-00 kubeadm=1.12.7-00 kubectl=1.12.7-00

sudo apt-mark hold kubelet kubeadm kubectl

#After installing these components, verify that Kubeadm is working by getting the version info.

kubeadm version

Boostrapping the Cluster

On the Kube master node, initialize the cluster:

sudo kubeadm init --pod-network-cidr=10.244.0.0/16

That command may take a few minutes to complete.

When it is done, set up the local kubeconfig:

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

Verify that the cluster is responsive and that Kubectl is working:

kubectl version

You should get Server Version as well as Client Version. It should look something like this:

The kubeadm init command should output a kubeadm join command containing a token and hash. Copy that command and run it with sudo on both worker nodes. It should look something like this:

sudo kubeadm join $some_ip:6443 --token $some_token --discovery-token-ca-cert-hash $some_hash

Verify that all nodes have successfully joined the cluster:

kubectl get nodes

You should see all three of your nodes listed. Note: The nodes are expected to have a STATUS of NotReady at this point.

Configuring Networking with Flannel

On master and nodes, run the following:

echo "net.bridge.bridge-nf-call-iptables=1" | sudo tee -a /etc/sysctl.conf
sudo sysctl -p

Install Flannel in the cluster by running this only on the Master node:

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/bc79dd1505b0c8681ece4de4c0d86c5cd2643275/Documentation/kube-flannel.yml

Verify that all the nodes now have a STATUS of Ready:

kubectl get nodes

You should see all three of your servers listed, and all should have a STATUS of Ready.

Note: It may take a few moments for all nodes to enter the Ready status, so if they are not all Ready, wait a few moments and try again.

It is also a good idea to verify that the Flannel pods are up and running. Run this command to get a list of system pods:

kubectl get pods -n kube-system

You should have three pods with flannel in the name, and all three should have a status of Running.

Pods and Containers

Create a simple pod running an nginx container:

  cat << EOF | kubectl create -f -
  apiVersion: v1
  kind: Pod
  metadata:
    name: nginx
  spec:
    containers:
    - name: nginx
      image: nginx
  EOF

Get a list of pods and verify that your new nginx pod is in the Running state:

kubectl get pods

Get more information about your nginx pod:

kubectl describe pod nginx

Delete the pod:

kubectl delete pod nginx

Get a list of nodes:

kubectl get nodes

Get more information about a specific node:

kubectl describe node shivansh_node

Networking

Networking is an important part of understanding the basics of Kubernetes.

Create a deployment with two nginx pods:

cat << EOF | kubectl create -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.15.4
        ports:
        - containerPort: 80
EOF

Create a busybox pod to use for testing:

cat << EOF | kubectl create -f -
apiVersion: v1
kind: Pod
metadata:
  name: busybox
spec:
  containers:
  - name: busybox
    image: radial/busyboxplus:curl
    args:
    - sleep
    - "1000"
EOF

Get the IP addresses of your pods:

kubectl get pods -o wide

Get the IP address of one of the nginx pods, then contact that nginx pod from the busybox pod using the nginx pod's IP address:

kubectl exec busybox -- curl $nginx_pod_ip

shivanshthapliyal/k8s-essentials.md