Steps to initialize k8s cluster
- Initialize the k8s cluster on node1
kubeadm init --apiserver-advertise-address=192.168.1.101 --pod-network-cidr=192.168.1.0/24 --v=5
IPADDR="192.168.1.101"
NODENAME=$(hostname -s)
POD_CIDR="192.168.1.0/16"
sudo kubeadm init --apiserver-advertise-address=$IPADDR --apiserver-cert-extra-sans=$IPADDR --pod-network-cidr=$POD_CIDR --node-name $NODENAME --ignore-preflight-errors Swap
To start using your cluster, you need to run the following as a regular user:
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
Alternatively, if you are the root user, you can run:
export KUBECONFIG=/etc/kubernetes/admin.conf
-
Setup Calico/WEAVE Net networking interface
Use any one of the following CNI setup, I used Weavenet
Calico
kubectl apply -f https://raw.githubusercontent.com/projectcalico/calico/v3.26.0/manifests/calico.yaml
Weavenet
kubectl apply -f https://github.com/weaveworks/weave/releases/download/v2.8.1/weave-daemonset-k8s.yaml
-
Join the other nodes with the node1
Paste the output from the node 1 to join the node 1
Vagrantfile and Scripts for setup
Ensure that the Vagrantfile and setup.sh are in the same folder.
Vagrantfile
Vagrant.configure("2") do |config|
config.vm.define "db1" do |db1|
db1.vm.box = "ubuntu/focal64"
db1.vm.hostname = 'db1'
db1.vm.box_url = "ubuntu/focal64"
db1.vm.provision "shell", path: "setup-k8s.sh"
db1.vm.provision "shell", path: "master.sh"
db1.vm.network "public_network", ip: '192.168.1.101', bridge: 'enp11s0'
db1.vm.provider :virtualbox do |v|
v.customize ["modifyvm", :id, "--natdnshostresolver1", "on"]
v.customize ["modifyvm", :id, "--memory", 2000]
v.customize ["modifyvm", :id, "--name", "db1"]
end
end
config.vm.define "db2" do |db2|
db2.vm.box = "ubuntu/focal64"
db2.vm.hostname = 'db2'
db2.vm.box_url = "ubuntu/focal64"
db2.vm.provision "shell", path: "setup-k8s.sh"
db2.vm.provision "shell", path: "worker.sh"
db2.vm.network "public_network", ip: '192.168.1.102', bridge: 'enp11s0'
db2.vm.provider :virtualbox do |v|
v.customize ["modifyvm", :id, "--natdnshostresolver1", "on"]
v.customize ["modifyvm", :id, "--memory", 2000]
v.customize ["modifyvm", :id, "--name", "db2"]
end
end
config.vm.define "db3" do |db3|
db3.vm.box = "ubuntu/focal64"
db3.vm.hostname = 'db3'
db3.vm.box_url = "ubuntu/focal64"
db3.vm.provision "shell", path: "setup-k8s.sh"
db3.vm.provision "shell", path: "worker.sh"
db3.vm.network "public_network", ip: '192.168.1.103', bridge: 'enp11s0'
db3.vm.provider :virtualbox do |v|
v.customize ["modifyvm", :id, "--natdnshostresolver1", "on"]
v.customize ["modifyvm", :id, "--memory", 2000]
v.customize ["modifyvm", :id, "--name", "db3"]
end
end
end
setup-k8s.sh
#!/bin/bash
set +xe
yes y | ssh-keygen -q -t rsa -N '' >/dev/null
echo "ssh-rsa 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 yash@yash-ThinkPad-P15-Gen-2i" >> ~/.ssh/authorized_keys
cat <<EOF >> /etc/hosts
192.168.1.101 db1
192.168.1.102 db2
192.168.1.103 db3
EOF
sudo swapoff -a
sudo apt-get install -y apt-transport-https
cat <<EOF | sudo tee /etc/modules-load.d/k8s.conf
overlay
br_netfilter
EOF
sudo modprobe overlay
sudo modprobe br_netfilter
# sysctl params required by setup, params persist across reboots
cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.ipv4.ip_forward = 1
EOF
# Apply sysctl params without reboot
sudo sysctl --system
sudo apt-get update
for pkg in docker.io docker-doc docker-compose podman-docker containerd runc; do sudo apt-get remove $pkg; done
sudo apt-get update
sudo apt-get install ca-certificates curl gnupg -y
sudo install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo gpg --dearmor -o /etc/apt/keyrings/docker.gpg
sudo chmod a+r /etc/apt/keyrings/docker.gpg
echo \
"deb [arch="$(dpkg --print-architecture)" signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu \
"$(. /etc/os-release && echo "$VERSION_CODENAME")" stable" | \
sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
sudo apt-get update
sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin -y
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=1.26.0-00 kubeadm=1.26.0-00 kubectl=1.26.0-00
sudo apt-mark hold kubelet kubeadm kubectl
sudo rm /etc/containerd/config.toml
#https://stackoverflow.com/questions/72504257/i-encountered-when-executing-kubeadm-init-error-issue
sudo systemctl restart containerd
apt-get install net-tools -y
master.sh (Setup to provision and initialize control node k8s)
#!/bin/bash
kubeadm init --apiserver-advertise-address=192.168.1.101 --pod-network-cidr=192.168.1.0/24 --v=5
IPADDR="192.168.1.101"
NODENAME=$(hostname -s)
POD_CIDR="192.168.1.0/16"
sudo kubeadm init --apiserver-advertise-address=$IPADDR --apiserver-cert-extra-sans=$IPADDR --pod-network-cidr=$POD_CIDR --node-name $NODENAME --ignore-preflight-errors Swap
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
echo "Setting up Weaveworks Network"
kubectl apply -f https://github.com/weaveworks/weave/releases/download/v2.8.1/weave-daemonset-k8s.yaml
kubectl get nodes
kubectl get pods --all-namespaces
kubectl cluster-info
kubeadm token create --print-join-command > index.html
docker run -dit -p 80:80 -v ./index.html:/usr/share/nginx/html/index.html nginx
cat ~/.kube/config > index-config.html
docker run -dit -p 8080:80 -v ./index-config.html:/usr/share/nginx/html/index.html nginx
**worker.sh** (Setup to provision the worker nodes)
#!/bin/bash
JOIN_COMMAND=$(curl db1:80)
echo "Following is the Join Command:- $JOIN_COMMAND"
$JOIN_COMMAND
curl db1:8080 > /etc/kubernetes/kubelet-admin.conf
echo "KUBECONFIG=/etc/kubernetes/kubelet-admin.conf" >> /etc/environment
source /etc/environment
Start the vms and provision them using setup.sh using the following command:
vagrant up
ssh into the vms using the following command:
vagrant ssh db1
Note: You might need to replace wlp9s0 with your own network interface along with the cidr ranges (here: 192.168.56.0/24).
Executing kubectl commands from worker nodes
By default your kubeconfig file of control node is not present in the worker node.
This means that you can only administer cluster from the control node.
In order to admin the cluster from the worker nodes as well, you will need to do the following configurations:-
-
Ensure that the kubectl config file from the control plane node is copied to the worker nodes.
Usually preset at ~/.kube/config on controller node.
Copy the control node kube config file data and paste it in a config file at the worker node.
Set the path using export KUBECONFIG=PATH/TO/YOUR/CONFIG (Can be located anywhere)
In my case I override /etc/kubernetes/kubelet.conf file with the kubeconfig of the control node.
Exposing the service (sample nginx application)
First download the sample manifest of nginx application created by nonanom.
curl -lo nginx.yaml "https://gist.githubusercontent.com/nonanom/498b913a69cede7037d55e28bb00344e/raw"
nginx.yaml
kind: Service
apiVersion: v1
metadata:
name: nginx
labels:
app: nginx
spec:
selector:
app: nginx
ports:
- port: 80
protocol: TCP
targetPort: 80
type: ClusterIP
---
apiVersion: apps/v1
kind: Deployment
metadata:
name: nginx
labels:
app: nginx
spec:
replicas: 1
selector:
matchLabels:
app: nginx
template:
metadata:
labels:
app: nginx
spec:
containers:
- name: nginx
image: nginx:latest
imagePullPolicy: Always
ports:
- containerPort: 80
protocol: TCP
-
Deploy the manifest in the cluster
kubectl apply --filename nginx.yaml
-
Expose the service (Portforward the service)
kubectl port-forward service/nginx --address 0.0.0.0 8080:80
Note: the node from where you execute the command for exposing the service will be the node from which you can access the application service.
Reference: https://nonanom.medium.com/run-nginx-on-kubernetes-ee6ea937bc99
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