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K8S Architecture

K8S on high level

  • A Kubernetes cluster consists of a master, which manages the cluster, and nodes, which run the services.
  • Developers and the deployment pipeline interact with Kubernetes through the API server, which along with other cluster-management software runs on the master.
  • Application containers run on nodes.
  • Each node runs a
    • Kubelet, which manages the application container
    • kube-proxy, which routes application requests to the pods, either directly as a proxy or indirectly by configuring iptables routing rules built into the Linux kernel.


Master Node

The master node consists of four components:

  • The API server - When you run commands on kubectl, this is what it communicated with to perform operations. The API server exposes an API for both external users and other components within the cluster.
  • The scheduler — This is responsible for selecting an appropriate node where a pod will run, given priority, resource needs, and other constraints.
  • The controller manager — This is responsible for executing control loops: the continual observe-diff-act operation that underpins the operation of Kubernetes.
  • A distributed key-value data store, etcd — This stores the underlying state of the cluster and thereby makes sure it persists when nodes fail or restarts are required.

Worker node

Each worker node uses the following components to run and monitor applications:

  • A container runtime — This can be Docker.
  • The kubelet — This interacts with the Kubernetes master to start, stop, and monitor containers on the node.
  • The kube-proxy — It is managing the virtual networking on each node. The proxy handles network routes and IP addressing for services and pods.


  • Control Groups: it is a feature of the Linux kernel that limits, accounts for, and isolates the resource usage (CPU, Memory, Disk I/O, Network, etc.) of a collection of processes.
  • CRI-O: It is a lightweight container runtime and was specifically designed for k8s by Red Hat.

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