| This page is updated in 2022 with new instructions which works for Rocky LInux as well! |
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| Kubernetes Cluster on your Desktop or Laptop or Mac book |
In this post, I would like to share the manual steps that work to build a Kubernetes Cluster on CentOS7. We will be using the Docker EE installed nodes to install Kubernetes. So bringing up vagrant boxes the same thing that we had discussed earlier post proceed further.
Step 1: Check the System requirements
We have three nodes: master, node1, node2.On ALL Nodes:
CPU Cores 2,
RAM size- 2GB Minimum 4GB good
Otherwise, Master node make it 3GB, Slave nodes with 1.5GB also a wise plan if you have limited resources.
Preparing the host mappings for master and worker nodes, Here I'm using sample names you can change as per your project needs.
hostnamectl set-hostname master-node cat << EOF >> /etc/hosts 10.128.0.27 master-node 10.128.0.29 node-1 worker-node-1 10.128.0.30 node-2 worker-node-2 EOFSetup the firewall rules
# master box run this
sudo firewall-cmd --zone=public --permanent --add-port={6443,2379,2380,10250,10251,10252}/tcp
# worker box firewall settings
sudo firewall-cmd --zone=public --permanent --add-port={10250,10251}/tcp
#for both boxes
firewall-cmd –reload
modprobe br_netfilter
echo '1' > /proc/sys/net/bridge/bridge-nf-call-iptables
Step 2: Why do we need to do swap disable?
All Kubernetes masters and nodes are expected to have swap disabled. This is recommended by Kubernetes community for deployments. If swap is not disabled, kubelet service will not start on the masters and nodes,# check swap available free -m # if exists then run the following commands swapoff -a # must for gcloud and aws instances # permanent swap off from fstab vi /etc/fstab --> comment swap entry
(OR) sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab
yum update -y systemctl disable firewalld systemctl stop firewalld vi /etc/selinux/config ---> disabled
Restart all of the boxes
init 6
Now install Docker if you have not installed yet! this following will installs Docker-CE.
yum install docker -y systemctl status docker #if it is inactive do the following systemctl enable docker systemctl start docker systemctl start docker # make sure it is active state
Step 4: Add Kubernetes Repo
This repo setting for CentOS boxes on ANY cloud env will works and same will work on vagrant box as well.vi /etc/yum.repos.d/kubernetes.repo
Enter the following content into the file
[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
Step 5: Install kubeadm, kubelet, kubectl and start
Now run the following yum installation commands on every node.yum install kubeadm -y #This will includes kubectl, kubelet part of kubeadmin installation systemctl enable kubelet systemctl start kubelet systemctl status kubelet # ensure kubelet is in active state
After starting kubeadm you will get the following:
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| Kubernetes Installation |
output
Let's configure bridge network for Kubernetes
vi /etc/sysctl.d/k8s.confEnter the following lines
net.bridge.bridge-nf-call-ip6tables = 1 net.bridge.bridge-nf-call-iptables = 1
After file saving run the following command in the command shell.
sysctl --system
In the Master node execute the following command for Kubernetes Cluster initialization:
# NOTE: Please use your host IP address here # This will do kubeadm init #alternatively try kubeadm init --pod-network-cidr=192.148.0.0/16 --apiserver-advertise-address=192.168.33.100 (OR) #To ignore preflight checks kubeadm init --pod-network-cidr=192.148.0.0/16 --apiserver-advertise-address=192.168.33.100 --ignore-preflight-errors=Hostname,SystemVerification,NumCPU
On the Worker / Slave nodes:
kubeadm join 192.168.33.100:6443 --token h1ufen.hvs0nr49ua0my7u8 \
--discovery-token-ca-cert-hash sha256:0bc179854b5c759333360737ff53ca2c4246b61823b033ecbac50593a9c334f6
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| Kubernetes Worker joining |
On the master node do the following:
vi /etc/profile export KUBECONFIG=/etc/kubernetes/admin.confRun the following: source /etc/profile
(OR)
mkdir -p $HOME/.kube cp -i /etc/kubernetes/admin.conf $HOME/.kube/config chown $(id -u):$(id -g) $HOME/.kube/config
Now
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| flannel network |
kubectl get nodes # all nodes NotReady state kubectl get pods --all-namespaces kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
kubectl get pods --all-namespaces kubectl get nodes
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| Get the status of the node in the Kubernetes cluster, after all pods Running |
Validate with Deployment
Let us validate the Kubernetes Cluster Ready for deploy web applicationStep 1 Let's take nginx image for deployment creation on the Kubernetes cluster
kubectl create deployment mynginx --image=nginx
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| First Kubernetes deployment : create deployment |
Now let's see the description of the above 'mynginx' deployment.
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| Describe Kubernetes deployment |
Scale the 'mynginx' application deployment upto 3
kubectl scale --replicas=3 deployment/mynginx
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| Scale deployment on Kubernetes Cluster |
List of all pods in the Kubernetes cluster
kubectl get po kubectl get po -o wide
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| get the list of pods in Kubernetes |
Next step is Create service using 'mynginx' deployment.
kubectl create service nodeport mynginx --tcp=8080:80
kubectl get services
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| Service creation in Kubernetes Cluster |
http://192.168.33.110:32286/
As our slave node running on 192.168.33.110 and the node port exposed as 32286.
Here I conclude our Kubernetes cluster working as expected! Please post your comments or suggestions to improve our learnings more useful to many other starters.
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