Kubernetes - Taints and Tolerations ☢️

Description 👀

Taints and Tolerations are features that allow you to control the placement of pods on nodes. Taints are applied to nodes, and tolerations are applied to pods.A taint on a node instructs the node to repel all pods that do not tolerate the taint.

Basic Commands 📝

Taints - Node

• taint-effect:   NoSchedule, PreferNoSchedule, NoExecute

• generic

  kubectl taint nodes <node-name> <key>=<value>:<taint-effect>
  

• example

  kubectl taint nodes node1 app=blue:NoSchedule
  

• to see if taints exist on a node

  kubectl describe node node01 | grep taint
  

Tolerations - Pod

spec:
  tolerations:
    - key: app
      operator: "Equal"
      value: blue
      effect: NoSchedule

Examples 🧩

• sample pod with tolerations definition

  apiVersion: v1
  kind: Pod
  metadata:
    name: my-app
  spec:
    containers:
      - name: nginx
        image: nginx
        tolerations:
          - key: app
            operator: "Equal"
            value: blue
            effect: NoSchedule
  

Bee and Mosquito Example 🐝🦟

• create node01 node

  apiVersion: v1
  kind: Node
  metadata:
    name: node01
  spec:
  

• create controlplane node

  apiVersion: v1
  kind: Node
  metadata:
    name: controlplane
    # add a taint with key spray and value mortien and effect NoSchedule
    taint: 
      - key: spray
        value: mortien
        effect: NoSchedule
  spec:
  

• apply taint

  kubectl taint nodes node01 spray=mortein:NoSchedule
  

• bee pod definition 🐝

  apiVersion: v1
  kind: Pod
  metadata:
    name: bee
  spec:
    containers:
      - name: nginx-bee
        image: nginx
    tolerations:
      - key: spray
        operator: "Equal"
        value: mortein
        effect: NoSchedule
  

• mosquito pod definition 🦟

  apiVersion: v1
  kind: Pod
  metadata:
    name: mosquito
  spec:
    containers:
      - name: nginx-mosquito
        image: nginx
  

• create the bee and mosquito pods and watch what happens
  • bee will be scheduled on node01 and mosquito will not be scheduled on any node
• remove the taint on controlplane
  • mosquito will be scheduled on controlplane

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