Skip to content

Latest commit

 

History

History

Day13

Folders and files

NameName
Last commit message
Last commit date

parent directory

..
readme.md
readme.md
 
 
task.md
task.md
 
 

readme.md

Day 13/40 - static pods, manual scheduling, labels, and selectors in Kubernetes 📘🚀

Check out the video below for Day13 👇

Day12/40 - Kubernetes Daemonset Explained - Daemonsets, Job and Cronjob in Kubernetes

Welcome to the quick reference guide for our Kubernetes Labels, Selectors, and Static Pods video! This guide will be handy as you dive deeper into Kubernetes, especially if you're starting. Let's explore these concepts in detail:

📌 Labels and Selectors in Kubernetes

Labels 🏷️

Labels are key-value pairs attached to Kubernetes objects like pods, services, and deployments. They help organize and group resources based on criteria that make sense to you.

Examples of Labels:

  • environment: production
  • type: backend
  • tier: frontend
  • application: my-app

Selectors 🔍

Selectors filter Kubernetes objects based on their labels. This is incredibly useful for querying and managing a subset of objects that meet specific criteria.

Common Usage:

  • Pods: kubectl get pods --selector app=my-app
  • Deployments: Used to filter the pods managed by the deployment.
  • Services: Filter the pods to which the service routes traffic.

Labels vs. Namespaces 🌍

  • Labels: Organize resources within the same or across namespaces.
  • Namespaces: Provide a way to isolate resources from each other within a cluster.

Annotations 📝

Annotations are similar to labels but attach non-identifying metadata to objects. For example, recording the release version of an application for information purposes or last applied configuration details etc.

🛠️ Static Pods

Static Pods are special types of pods managed directly by the kubelet on each node rather than through the Kubernetes API server.

Key Characteristics of Static Pods:

  • Not Managed by the Scheduler: Unlike deployments or replicasets, the Kubernetes scheduler does not manage static pods.
  • Defined on the Node: Configuration files for static pods are placed directly on the node's file system, and the kubelet watches these files.
  • Some examples of static pods are: ApiServer, Kube-scheduler, controller-manager, ETCD etc

Managing Static Pods:

  1. SSH into the Node: You will gain access to the node where the static pod is defined.(Mostly the control plane node)
  2. Modify the YAML File: Edit or create the YAML configuration file for the static pod.
  3. Remove the Scheduler YAML: To stop the pod, you must remove or modify the corresponding file directly on the node.
  4. Default location": is usually /etc/kubernetes/manifests/; you can place the pod YAML in the directory, and Kubelet will pick it for scheduling.

🧭 Manual Pod Scheduling

Manual scheduling in Kubernetes involves assigning a pod to a specific node rather than letting the scheduler decide.

Key Points:

  • nodeName Field: Use this field in the pod specification to specify the node where the pod should run.
  • No Scheduler Involvement: When nodeName is specified, the scheduler bypasses the pod, and it’s directly assigned to the given node.

Example Configuration:

apiVersion: v1
kind: Pod
metadata:
  name: manual-scheduled-pod
spec:
  nodeName: worker-node-1
  containers:
  - name: nginx
    image: nginx

Note: Kubernetes will place the pod on worker-node-1 with the above configuration.