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Curious about how Kubernetes gets things done effortlessly? 🤔 Discover the magic behind scheduling Pods in this fascinating sequence diagram! 📈

🔑 Key Takeaways:

👉📝 The user creates a Pod via the API Server ✨🖥️

📥 The API server writes it to etcd 📝🔒

🔍 The scheduler notices an “unbound” Pod and decides which node to run that Pod on 🧭🏃‍♀️

📝 Scheduler writes that binding back to the API Server 🖊️🔙

🔄 The Kubelet notices a change in the set of Pods that are bound to its node 🔄🔧

🐳 Kubelet, in turn, runs the container via the container runtime (i.e. Docker) 🚢🏃‍♂️

👀 The Kubelet monitors the status of the Pod via the container runtime 🕵️‍♂️💬

🔄 As things change, the Kubelet will reflect the current status back to the API Server 🔄🔄💡

🌟 Dive into the orchestration magic of Kubernetes! 🚀 Embrace the containerized journey with ease! 🎯 #KubernetesWorkflow #ContainerMagic #DevOpsTech 🌐

By using the API Server as a central coordination point, Kubernetes is able to have a set of components interact with each other in a loosely coupled manner.

Kubernetes Control Plane

API Server

The API server is a component of the Kubernetes control plane that exposes the Kubernetes API. 

The API server is the front end for the Kubernetes control plane.

The main implementation of a Kubernetes API server is kube-apiserver. 

kube-apiserver is designed to scale horizontally—that is, it scales by deploying more instances. 

You can run several instances of kube-apiserver and balance traffic between those instances.

ETCD

Consistent and highly-available key value store.

It is used as Kubernetes’ backing store for all cluster data.

Backup and restore is a must.

Scheduler

Control plane component that watches for newly created Pods with no assigned node, 

And selects a node for them to run on.

Factors taken into account for scheduling decisions include: 

1.Individual and collective resource requirements, 

2.Hardware/software/policy constraints, 

3.Affinity and anti-affinity specifications, 

4.Data locality, 

5.Inter-workload interference, and deadlines. 

Kubernetes Node

Kubelet

An agent that runs on each node in the cluster. 

It makes sure that containers are running in a Pod.

The kubelet takes a set of PodSpecs that are provided through various mechanisms and ensures that the containers described in those PodSpecs are running and healthy. 

The kubelet doesn’t manage containers which were not created by Kubernetes.

Docker

Is an open source DevOps tool designed to help developers & operations guys to streamline application development and deployment.

By dockerizing an application means deploying and running an application using containers.

Containers allow a developer to package up an application with all of the parts it needs, such as libraries and other dependencies, and deploy it as one package.

Now, we need YOUR support to spread the word! 🙌

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Prerequisites :-

• 2 Ubuntu 20.04 LTS Virtual Machines
• 2 CPU, 4 GB RAM for Master node
• 1 CPU, 2 GB RAM for Worker Node

Step1: Install Docker engine and kubeadm on Master and Worker Nodes

apt-get update  
apt-get install docker.io -y
service docker restart  
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -  
echo "deb http://apt.kubernetes.io/ kubernetes-xenial main" >/etc/apt/sources.list.d/kubernetes.list
apt-get update
apt install kubeadm=1.20.0-00 kubectl=1.20.0-00 kubelet=1.20.0-00 -y

Step2: Joining Worker Node to the Master

On Master node run below command

kubeadm init --pod-network-cidr=192.168.0.0/16

Copy the token and use it into the worker node command

Step3: Run kubectl commands as non-root user On Master

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

Step4: Run below commands on master node to Deploy Calico network

curl https://raw.githubusercontent.com/projectcalico/calico/v3.25.0/manifests/calico.yaml -O
kubectl apply -f calico.yaml
kubectl apply -f https://raw.githubusercontent.com/kubernetes/ingress-nginx/controller-v0.49.0/deploy/static/provider/baremetal/deploy.yaml

Run commands mentioned in this doc to https://beginner.academy/kubernetes-shortcuts/ validate Kubernetes cluster & perform deployment verification test.

What is DevOps?

The full form of DevOps is Development Operations.

DevOps is the union of people, process, and technology to continually provide value to costumers.

In simple terms DevOps speeds up the process of delivering applications and software services.

Kubernetes Main Resources

✔𝗡𝗼𝗱𝗲: A Node is a Kubernetes cluster’s worker computer. Either a physical or virtual machine may be used. The operating and management of the pods is done by the nodes.

✔𝗡𝗮𝗺𝗲𝘀𝗽𝗮𝗰𝗲: The cluster resources can be split up into virtual clusters using namespaces. It gives names a range and enables many teams or projects to share the same physical cluster while isolating their resources.

✔Deployment : simplifies the process of managing and controlling the lifecycle of applications in a Kubernetes cluster, making it easier to deploy and update applications with minimal downtime and manual intervention.

✔𝗥𝗲𝗽𝗹𝗶𝗰𝗮𝗦𝗲𝘁: ReplicaSets are Kubernetes objects that guarantee a certain number of pod replicas are always active. Scaling and managing the number of pods for a certain application are done using it.

✔Ingress: in Kubernetes is an API object that serves as an entry point for external traffic into the cluster, acting as a layer between the external world and the services running inside.

✔𝗦𝗲𝗿𝘃𝗶𝗰𝗲: A logical set of pods and a policy for accessing them are defined by a service, which is an abstraction. For the pods behind it, it offers a reliable network endpoint (IP address) and load balancing.

✔𝗣𝗼𝗱: A Pod is the smallest and most basic unit in Kubernetes. It represents a single instance of a running process or a set of tightly coupled processes running together on a node. Pods are scheduled and managed by Kubernetes.

✔Network policies: in Kubernetes are a set of rules that control the traffic flow between pods within a cluster. Network policies enhance security and provide granular control over network traffic within the cluster.

✔Persistent Volumes (PVs): Kubernetes are storage resources that provide durable and independent storage for applications. PVs enable data persistence and can be dynamically provisioned or statically allocated within the cluster.

✔Persistent Volume Claims : (PVCs) in Kubernetes are requests made by applications for storage resources. PVCs provide a convenient abstraction layer, allowing applications to request and access persistent storage without directly dealing with specific PVs.

✔Service Accounts: in Kubernetes are used to provide an identity and access control for pods within the cluster. Service Accounts facilitate secure communication and authorization between pods and the Kubernetes cluster.

✔Storage Classes : in Kubernetes are used to dynamically provision different types of storage volumes based on predefined configurations.It enable flexibility and scalability in allocating storage for applications within the cluster.

Kubernetes Shortcuts

kubectl get no
kubectl get ns
kubectl get deploy
kubectl get rs
kubectl get ing
kubectl get svc
kubectl get po
kubectl get netpol
kubectl get pv
kubectl get pvc
kubectl get sa
kubectl get sc

Beginner Academy

Resource	Shortcuts	Command
Node	no	kubectl get no
Namespace	ns	kubectl get ns
Deployment	deploy	kubectl get deploy
Replica Set	rs	kubectl get rs
Ingress	ing	kubectl get ing
Services	svc	kubectl get svc
Pod	po	kubectl get po
Network policies	netpol	kubectl get netpol
Persistent Volumes	pv	kubectl get pv
Persistent Volume Claims	pvc	kubectl get pvc
Service Accounts	sa	kubectl get sa
Storage Classes	sc	kubectl get sc

Kubernetes frequently used Commands

1. kubectl get: Retrieve information about resources in the cluster.
   kubectl get pods: List all pods.
   kubectl get deployments: List all deployments.
   kubectl get services: List all services.
   kubectl get nodes: List all nodes in the cluster.

kubectl get pods
kubectl get deployments
kubectl get services
kubectl get nodes

2.kubectl describe: Provide detailed information about a specific resource.
kubectl describe pod <pod-name>: Get detailed information about a pod.
kubectl describe deployment <deployment-name>: Get detailed information about a deployment.
kubectl describe service <service-name>: Get detailed information about a service.

kubectl describe pod <pod-name>
kubectl describe deployment <deployment-name>
kubectl describe service <service-name>

3.kubectl create: Create a resource from a YAML or JSON file.
kubectl create -f <filename.yaml>: Create a resource from a YAML file.
kubectl create deployment <deployment-name> — image=<image-name>: Create a deployment using a specified image.

kubectl create -f <filename.yaml>
kubectl create deployment <deployment-name> - image=<image-name>

4.kubectl delete: Delete a resource.
kubectl delete pod <pod-name>: Delete a pod.
kubectl delete deployment <deployment-name>: Delete a deployment.
kubectl delete service <service-name>: Delete a service.

kubectl delete pod <pod-name>
kubectl delete deployment <deployment-name>
kubectl delete service <service-name>

5.kubectl scale: Scale the number of replicas in a deployment.
kubectl scale deployment <deployment-name> — replicas=<number>: Scale the number of replicas for a deployment.

kubectl scale deployment <deployment-name> - replicas=<number>

6.kubectl logs: Print the logs of a pod.
kubectl logs <pod-name>: Print the logs of a pod.

kubectl logs <pod-name>

7.kubectl exec: Execute a command on a pod.
kubectl exec -it <pod-name> — <command>: Execute a command on a pod interactively.

kubectl exec -it <pod-name> - <command>

8.kubectl apply: Apply changes to a resource defined in a YAML or JSON file.
kubectl apply -f <filename.yaml>: Apply changes to a resource using a YAML file.

kubectl apply -f <filename.yaml>