See these pages for more details about Kubernetes:
https://kubernetes.io/docs/concepts/overview/components/
https://kubernetes.io/docs/concepts/cluster-administration/
https://kubernetes.io/docs/concepts/cluster-administration/proxies/
https://kubernetes.io/docs/reference/access-authn-authz/admission-controllers/
https://kubernetes.io/docs/tasks/debug/debug-cluster/

To install Kubernetes using Docker Desktop (Windows - WSL 2): Install Docker Desktop (WSL 2) and Enable Kubernetes

Amazon Elastic Kubernetes Service (EKS): https://docs.aws.amazon.com/eks/latest/userguide/what-is-eks.html

Microsoft Azure Kubernetes Service (AKS): https://learn.microsoft.com/en-us/azure/aks/

Google Kubernetes Engine (GKE): https://cloud.google.com/kubernetes-engine/docs

To List the nodes of the cluster:
$ kubectl get nodes -o wide NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP OS-IMAGE KERNEL-VERSION CONTAINER-RUNTIME docker-desktop Ready control-plane 9h v1.32.2 192.168.65.3 <none> Docker Desktop 5.15.167.4-microsoft-standard-WSL2 docker://28.0.4
Depending on your installation you might see at least one node with the role "master" (the control plane: kube-apiserver, etcd) and eventually a list of worker nodes (where the containers are scheduled).

To get information about a node:
$ kubectl get nodes docker-desktop -o yaml apiVersion: v1 kind: Node metadata: annotations: kubeadm.alpha.kubernetes.io/cri-socket: unix:///var/run/cri-dockerd.sock labels: beta.kubernetes.io/arch: amd64 beta.kubernetes.io/os: linux kubernetes.io/arch: amd64 kubernetes.io/hostname: docker-desktop kubernetes.io/os: linux name: docker-desktop spec: {} ...
To describe a node:
$ kubectl describe nodes docker-desktop Name: docker-desktop Roles: control-plane Labels: beta.kubernetes.io/arch=amd64 beta.kubernetes.io/os=linux kubernetes.io/arch=amd64 kubernetes.io/hostname=docker-desktop kubernetes.io/os=linux Annotations: kubeadm.alpha.kubernetes.io/cri-socket: unix:///var/run/cri-dockerd.sock ...
The commands above show information about the node (hostname, processor, OS, ...), its capacity (CPU, memory, ...), the Pods running on it (their names, CPU/Memory requests and limits), the total allocated resources (CPU/Memory requests and limits), the conditions of the pressure on the disk and the memory, and the version of some system components is also printed (Linux Kernel, Container Runtime, Kubelet, ...).

To show the resources usage in the cluster:
$ kubectl top nodes NAME CPU(cores) CPU(%) MEMORY(bytes) MEMORY(%) docker-desktop 188m 0% 3880Mi 12%
If the metric server is not installed, you will get this error: "error: Metrics API not available".
For more details see: Kubernetes Metrics Server

To show the resources usage by the pods:
$ kubectl top pods NAME CPU(cores) MEMORY(bytes) hello-nginx 0m 21Mi
To print the events in the cluster:
$ kubectl get events LAST SEEN TYPE REASON OBJECT MESSAGE 1m Normal Pulling pod/hello-busybox Pulling image "busybox:latest" ...

If you have installed Docker Desktop, you will see that Kubernetes is using CoreDNS DNS server.

The DNS server is used as the internal Kubernetes DNS service (cluster DNS) that provides naming and discovery for all Kubernetes Services that are created in the cluster.

The CoreDNS is running as a Kubernetes Deployment (replicas of Pods) and has a Service (acts as a load balancer for the DNS server).

The CoreDNS server components run in the "kube-system" namespace (can be filtered with the label "k8s-app=kube-dns").

To see the CoreDNS Deployment:
$ kubectl get deployments -n kube-system -l k8s-app=kube-dns -o wide NAME READY UP-TO-DATE AVAILABLE AGE CONTAINERS IMAGES SELECTOR coredns 2/2 2 2 9h coredns registry.k8s.io/coredns/coredns:v1.11.3 k8s-app=kube-dns
To see the CoreDNS Pods:
$ kubectl get pods -n kube-system -l k8s-app=kube-dns -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES coredns-668d6bf9bc-mjgnv 1/1 Running 0 9h 10.1.0.26 docker-desktop <none> <none> coredns-668d6bf9bc-mrs79 1/1 Running 0 9h 10.1.0.27 docker-desktop <none> <none>
To see the CoreDNS Service (kube-dns):
$ kubectl get services -n kube-system -l k8s-app=kube-dns -o wide NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE SELECTOR kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP,9153/TCP 9h k8s-app=kube-dns
Let's install dnsutils utility to help debuging the DNS name resolution for services:
$ kubectl apply -f https://k8s.io/examples/admin/dns/dnsutils.yaml pod/dnsutils created
Check that Pod was created properly:
$ kubectl get pod dnsutils NAME READY STATUS RESTARTS AGE dnsutils 1/1 Running 0 56s
First let's validate that the DNS resolution is working correctly.
The nslookup command can be used to resolve the "kubernetes" Service of the API Server (you should get something like the following):
$ kubectl exec -i -t dnsutils -- nslookup kubernetes Server: 10.96.0.10 <- The IP address of the Kubernetes DNS Address: 10.96.0.10#53 Name: kubernetes.default.svc.cluster.local <- The FQDN of the "kubernetes" Service Address: 10.96.0.1 <- The clusterIP of the "kubernetes" Service
Let's check the "/etc/resolv.conf" file (the search path and name server should look like the following):
$ kubectl exec dnsutils -- cat /etc/resolv.conf nameserver 10.96.0.10 <- Kubernetes DNS IP address (kube-dns Service ClusterIP) search default.svc.cluster.local svc.cluster.local cluster.local <- Kubernetes DNS search domains options ndots:5
The "nameserver" (DNS IP address) and "search" (DNS search domains) are saved in the "/etc/resolv.conf" file of all containers.

kube-proxy is a network proxy that runs on each node in the Kubernetes cluster. It routes network traffic (from inside or outside of the Kubernetes cluster) to Pods of load-balanced services.

The CoreDNS is running as a Kubernetes DaemonSet in the "kube-system" namespace (can be filtered with the label "k8s-app=kube-proxy").

To see the "kube proxy" DaemonSet and its Pod:
$ kubectl get all -n kube-system -l k8s-app=kube-proxy -o wide NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES pod/kube-proxy-4xt54 1/1 Running 0 10h 192.168.65.3 docker-desktop <none> <none> NAME DESIRED CURRENT READY UP-TO-DATE AVAILABLE NODE SELECTOR AGE CONTAINERS IMAGES SELECTOR daemonset.apps/kube-proxy 1 1 1 1 1 kubernetes.io/os=linux 10h kube-proxy registry.k8s.io/kube-proxy:v1.32.2 k8s-app=kube-proxy