I am trying to understand the cluster components and networking concepts and fol . . .

Kubernetes
#1

Mayur Sharma:
I am trying to understand the cluster components and networking concepts and following are few of the things I learnt, let me know if they are right or anything wrong in my understanding,

  1. Kubelet : Installed on worker node as a service(always)
    kubeconfig file – stores the cluster information like apiserver URL:port, username and its certificates
    config file – stores which cni plugin would be used and other parameters like bin dir and conf dir
    stores the range of IP that would be assign to pod it creates

  2. Kube-proxy : not sure how it is installed. but handles services networking,
    create iptables mapping for service name/ip to pod IPs

  3. Pod networking: how pod IP are managed and determine how pod are accessible to other pods, irrespective of pod deployment on node
    kubelet handles and configures network plugin like weave, which does all pod networking related
    things like put container on pod network

  4. Service networking : Service becomes available accross the cluster,
    KubeDNS stores service name and its IP in it as DNS name
    kube-proxy creates the mapping for service IP to pod ip it should redirect

  5. CoreDNS : How service names are resolved – /etc/reso
    /etc/hosts is present on each node, and can contain name-to-ip mapping but very hard to manage in big cluster
    moved all entries into central server and put that central server ip in
    /etc/resolv.conf file
    nameserver <ip of DNS server service>
    Deployed as pod and service

#2

Ravan Nannapaneni:
2. Kube proxy is deploy as a daemonset, this will ensure kube-proxy runs on all nodes - helping network all pods on these nodes.

  1. CoreDNS is deployed as a deploymentset
#3

Mayur Sharma:
@Ravan Nannapaneni: Where can I find the yaml file for kube-proxy and coreDNS like we have other component file is at /etc/kubernetes/manifest (static pod location defined in kubelet configuration)
Also, for CKA exam perspective, should we know how to install them on box

#4

Ravan Nannapaneni:
kubectl get deploy coredns -n kube-system -o yaml

#5

Ravan Nannapaneni:
kubectl get ds kube-proxy -n kube-system -o yaml

#6

Mayur Sharma:
@Ravan Nannapaneni: yeah, thank you :slightly_smiling_face: . do we also expect that in CKA exam, we can be asked to install anyone of them from scratch?