06-Taints-and-Tolerations.md

Taints and Tolerations

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In this section, we will take a look at taints and tolerations.

• Pod to node relationship and how you can restrict what pods are placed on what nodes.

Taints and Tolerations are used to set restrictions on what pods can be scheduled on a node.

• Only pods which are tolerant to the particular taint on a node will get scheduled on that node.

  

Taints

• Use kubectl taint nodes command to taint a node.

  Syntax

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

  Example

  $ kubectl taint nodes node1 app=blue:NoSchedule
  

• The taint effect defines what would happen to the pods if they do not tolerate the taint.

• There are 3 taint effects

  • NoSchedule
  • PreferNoSchedule
  • NoExecute

  

Tolerations

• Tolerations are added to pods by adding a tolerations section in pod definition.

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

Taints and Tolerations do not tell the pod to go to a particular node. Instead, they tell the node to only accept pods with certain tolerations.

• To see this taint, run the below command

  $ kubectl describe node kubemaster |grep Taint
  

K8s Reference Docs

• https://kubernetes.io/docs/concepts/scheduling-eviction/taint-and-toleration/