Kubernetes is a cluster and orchestration engine for docker containers. In other words Kubernetes is an open source software or tool which is used to orchestrate and manage docker containers in cluster environment. Kubernetes is also known as k8s and it was developed by Google and donated to “Cloud Native Computing foundation”

In Kubernetes setup we have one master node and multiple nodes. Cluster nodes is known as worker node or Minion. From the master node we manage the cluster and its nodes using ‘kubeadm‘ and ‘kubectl‘ command.

Kubernetes can be installed and deployed using following methods:

Minikube ( It is a single node kubernetes cluster)

Kops ( Multi node kubernetes setup into AWS )

Kubeadm ( Multi Node Cluster in our own premises)

In this article we will install latest version of Kubernetes 1.7 on CentOS 7 / RHEL 7 with kubeadm utility. In my setup I am taking three CentOS 7 servers with minimal installation. One server will acts master node and rest two servers will be minion or worker nodes.

On the Master Node following components will be installed

API Server – It provides kubernetes API using Jason / Yaml over http, states of API objects are stored in etcd

– It provides kubernetes API using Jason / Yaml over http, states of API objects are stored in etcd Scheduler – It is a program on master node which performs the scheduling tasks like launching containers in worker nodes based on resource availability

– It is a program on master node which performs the scheduling tasks like launching containers in worker nodes based on resource availability Controller Manager – Main Job of Controller manager is to monitor replication controllers and create pods to maintain desired state.

– Main Job of Controller manager is to monitor replication controllers and create pods to maintain desired state. etcd – It is a Key value pair data base. It stores configuration data of cluster and cluster state.

– It is a Key value pair data base. It stores configuration data of cluster and cluster state. Kubectl utility – It is a command line utility which connects to API Server on port 6443. It is used by administrators to create pods, services etc.

On Worker Nodes following components will be installed

Kubelet – It is an agent which runs on every worker node, it connects to docker and takes care of creating, starting, deleting containers.

– It is an agent which runs on every worker node, it connects to docker and takes care of creating, starting, deleting containers. Kube-Proxy – It routes the traffic to appropriate containers based on ip address and port number of the incoming request. In other words we can say it is used for port translation.

– It routes the traffic to appropriate containers based on ip address and port number of the incoming request. In other words we can say it is used for port translation. Pod – Pod can be defined as a multi-tier or group of containers that are deployed on a single worker node or docker host.

Installations Steps of Kubernetes 1.7 on CentOS 7 / RHEL 7

Perform the following steps on Master Node

Step 1: Disable SELinux & setup firewall rules

Login to your kubernetes master node and set the hostname and disable selinux using following commands

~]# hostnamectl set-hostname 'k8s-master' ~]# exec bash ~]# setenforce 0 ~]# sed -i --follow-symlinks 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux

Set the following firewall rules.

Note: In case you don’t have your own dns server then update /etc/hosts file on master and worker nodes

192.168.1.30 k8s-master 192.168.1.40 worker-node1 192.168.1.50 worker-node2

Disable Swap in all nodes using “swapoff -a” command and remove or comment out swap partitions or swap file from fstab file

Step 2: Configure Kubernetes Repository

Kubernetes packages are not available in the default CentOS 7 & RHEL 7 repositories, Use below command to configure its package repositories.

Step 3: Install Kubeadm and Docker

Once the package repositories are configured, run the beneath command to install kubeadm and docker packages.

[[email protected] ~]# yum install kubeadm docker -y

Start and enable kubectl and docker service

[[email protected] ~]# systemctl restart docker && systemctl enable docker [[email protected] ~]# systemctl restart kubelet && systemctl enable kubelet

Step 4: Initialize Kubernetes Master with ‘kubeadm init’

Run the beneath command to initialize and setup kubernetes master.

Output of above command would be something like below

As we can see in the output that kubernetes master has been initialized successfully. Execute the beneath commands to use the cluster as root user.

Step 5: Deploy pod network to the cluster

Try to run below commands to get status of cluster and pods.

To make the cluster status ready and kube-dns status running, deploy the pod network so that containers of different host communicated each other. POD network is the overlay network between the worker nodes.

Run the beneath command to deploy network.

[[email protected] ~]# export kubever=$(kubectl version | base64 | tr -d '

') [[email protected] ~]# kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$kubever" serviceaccount "weave-net" created clusterrole "weave-net" created clusterrolebinding "weave-net" created daemonset "weave-net" created [[email protected] ~]#

Now run the following commands to verify the status

[[email protected] ~]# kubectl get nodes NAME STATUS AGE VERSION k8s-master Ready 1h v1.7.5 [[email protected] ~]# kubectl get pods --all-namespaces NAMESPACE NAME READY STATUS RESTARTS AGE kube-system etcd-k8s-master 1/1 Running 0 57m kube-system kube-apiserver-k8s-master 1/1 Running 0 57m kube-system kube-controller-manager-k8s-master 1/1 Running 0 57m kube-system kube-dns-2425271678-044ww 3/3 Running 0 1h kube-system kube-proxy-9h259 1/1 Running 0 1h kube-system kube-scheduler-k8s-master 1/1 Running 0 57m kube-system weave-net-hdjzd 2/2 Running 0 7m [[email protected] ~]#

Now let’s add worker nodes to the Kubernetes master nodes.

Perform the following steps on each worker node

Step 1: Disable SELinux & configure firewall rules on both the nodes

Before disabling SELinux set the hostname on the both nodes as ‘worker-node1’ and ‘worker-node2’ respectively

~]# setenforce 0 ~]# sed -i --follow-symlinks 's/SELINUX=enforcing/SELINUX=disabled/g' /etc/sysconfig/selinux ~]# firewall-cmd --permanent --add-port=10250/tcp ~]# firewall-cmd --permanent --add-port=10255/tcp ~]# firewall-cmd --permanent --add-port=30000-32767/tcp ~]# firewall-cmd --permanent --add-port=6783/tcp ~]# firewall-cmd --reload ~]# echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables

Step 2: Configure Kubernetes Repositories on both worker nodes

~]# cat <<EOF > /etc/yum.repos.d/kubernetes.repo > [kubernetes] > name=Kubernetes > baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64 > enabled=1 > gpgcheck=1 > repo_gpgcheck=1 > gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg > https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg > EOF

Step 3: Install kubeadm and docker package on both nodes

[[email protected] ~]# yum install kubeadm docker -y [[email protected] ~]# yum install kubeadm docker -y

Start and enable docker service

[[email protected] ~]# systemctl restart docker && systemctl enable docker [[email protected] ~]# systemctl restart docker && systemctl enable docker

Step 4: Now Join worker nodes to master node

To join worker nodes to Master node, a token is required. Whenever kubernetes master initialized , then in the output we get command and token. Copy that command and run on both nodes.

Output of above command would be something like below

Output would be something like below

Now verify Nodes status from master node using kubectl command

[[email protected] ~]# kubectl get nodes NAME STATUS AGE VERSION k8s-master Ready 2h v1.7.5 worker-node1 Ready 20m v1.7.5 worker-node2 Ready 18m v1.7.5 [[email protected] ~]#

As we can see master and worker nodes are in ready status. This concludes that kubernetes 1.7 has been installed successfully and also we have successfully joined two worker nodes. Now we can create pods and services.

Please share your feedback and comments in case this article helps you to install latest version of kubernetes 1.7