Kubernetes Cheetbook

August 07, 2023

1. Basics:

  • Pods: Smallest deployable units in Kubernetes that can hold one or multiple containers.
  • Nodes: Worker machines in Kubernetes.
  • Clusters: A set of worker machines, called nodes, that run containerized applications.
  • Kubectl: Command-line tool for interacting with a Kubernetes cluster.
  • Kubelet: An agent running on each node in the cluster.
  • API Server: Front-end to the cluster's control plane.
  • Etcd: Consistent and highly-available key-value store used as Kubernetes' backing store for all cluster data.
  • Control Plane: The collection of processes that control Kubernetes nodes.
  • Namespace: Virtual clusters backed by the same physical cluster.

2. Workloads & Controllers:

  • Deployments: Manages a replicated application.
  • ReplicaSets: Ensures that a specified number of replicas of a Pod are running at all times.
  • StatefulSets: Manages the deployment and scaling of a set of Pods,providing guarantees about ordering and uniqueness.
  • DaemonSets: Ensures that all (or some) nodes run a copy of a Pod.
  • Jobs: Creates one or more Pods and ensures that a specified number of them successfully terminate.
  • CronJobs: Manages time-based Jobs, such as running a Job at a specific time or periodic intervals.
  • Horizontal Pod Autoscaler: Automatically scales the number of Pods in a deployment, replica set, or replication controller based on observed CPU or memory usage.

3. Services & Networking:

  • Services: A way to expose an application running in Pods as a network service. 
  • Ingress: Manages external access to services within a cluster.
  • Network Policies: Define how Pods communicate with each other.
  • Service Discovery: Mechanism to connect to services dynamically based on a logical name.
  • Load Balancer: A service that distributes network traffic across multiple Pods.

4. Configuration & Secrets:

  • ConfigMaps: Manage configuration data separately from container images.
  • Secrets: Manages sensitive information, such as passwords, OAuth tokens, and ssh keys.
  • Environment Variables: Used within Kubernetes for service discovery.
  • Volumes: Persistent storage in Kubernetes.
  • Persistent Volume Claims (PVCs): Request for storage by a user.

5. Monitoring, Logging, and Debugging:

  • Kube-state-metrics: A simple service that listens to the Kubernetes API server and generates metrics about the state of the objects.
  • Prometheus: An open-source system monitoring and alerting toolkit.
  • Grafana: Open platform for beautiful analytics and monitoring (often used with Prometheus).
  • ELK Stack: Elasticsearch, Logstash, and Kibana used for logging in Kubernetes.
  • Kubernetes Dashboard: General-purpose web UI for Kubernetes clusters.
  • Kubectl Debug: Tool for debugging pods.
  • Heapster: Collects monitoring and performance metrics.

6. Security & Authorization:

  • Role-Based Access Control (RBAC): Access control system.
  • Security Policies: Security constraints applied to a Pod.
  • Service Account: Identity attached to Pods to interact with the Kubernetes API Server.
  • Transport Layer Security (TLS): Protocol for privacy and data integrity.

7. Kubernetes Storage:

  • Persistent Volumes (PVs): Offers storage to the cluster that is independent of Pod life cycles.
  • Storage Classes: Allow administrators to describe the "classes" of storage offered.

8. Kubernetes Cluster Maintenance:

  • Node Maintenance: Taking a node down for service or replacing a failing node.
  • Cluster Upgrades: Upgrading the cluster to a newer Version.
  • Backup and Disaster Recovery: Ensuring data continuity and integrity.

9. Extending Kubernetes:

  • Custom Resources: Extension of the Kubernetes API.
  • API Server Extension: Custom endpoints in the Kubernetes API.
  • Custom Controllers: Automate handling of Custom Resources.
  • Operators: Application-specific controllers to create, configure, and manage instances of complex stateful applications.

10. Advanced Features:

  • Service Mesh (e.g., Istio): Manage microservices in a transparent way.
  • Pod Priority & Preemption: Specifies priorities for Pods and allows preemption of lower-priority Pods.
  • Taints and Tolerations: Allows a node to repel a set of Pods.
  • Node Affinity: Controls where a Pod runs based on labels on nodes and conditions called node affinity rules.
  • Pod Presets: Injects information like secrets, volume mounts, and environment variables into pods at creation time.

11. Kubernetes Cloud Integration:

  • Amazon EKS: Managed Kubernetes service on AWS.
  • Google Kubernetes Engine (GKE): Managed Kubernetes service on Google Cloud.
  • Azure AKS: Managed Kubernetes service on Azure.

12. Continuous Deployment/Integration in Kubernetes:

  • Jenkins: Popular open-source tool to perform continuous integration and build automation.
  • GitLab CI: Continuous integration service included with GitLab that builds and tests the software whenever a developer pushes code to the application.
  • Spinnaker: Open-source, multi-cloud continuous delivery platform for releasing software changes with high velocity and confidence.

13. Helm: Kubernetes Package Manager:

  • Helm Charts: Packages of pre-configured Kubernetes resources.
  • Helm Repository: A collection of charts for Kubernetes packages.

14. Kubernetes Custom Scheduling:

  • Custom Scheduler: You can implement a custom scheduler to have more control over the scheduling of your Pods.
15. Kubernetes Federation:
  • Cluster Federation: Allows the synchronization of resources cross multiple clusters.

16. Kubernetes Automation and Autoscaling:

  • Cluster Autoscaler: Automatically adjusts the size of the cluster, scaling it up or down as necessary.
  • Vertical Pod Autoscaler: Automatically adjusts the amount of CPU and memory requested by containers in a Pod.
  • Horizontal Pod Autoscaler (HPA): Automatically scales the number of Pods in a deployment or replica set based on observed CPU or memory utilization.

17. Kubernetes Development Tools:

  • MicroK8s :  is the simplest production-grade conformant K8s. Lightweight and focused. Single command install on Linux, Windows and macOS
  • Minikube: Runs a single-node Kubernetes cluster inside a VM on your laptop for users looking to try out Kubernetes or develop with it day-to-day.
  • Kompose: Conversion tool for all Docker Compose users to help them move to Kubernetes.
  • Kubeadm: Tool for bootstrapping a best-practice Kubernetes cluster.

Ref: 

1. https://kubernetes.io/
2. https://en.wikipedia.org/wiki/Kubernetes
3. https://github.com/kubernetes/kubernetes

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