Config - Taints and Tolerations

Question 1

What are Taints and Tolerations used for?

Answer 1

• used for creating restrictions, what pods can be deployed on what nodes

Question 2

When can Taints and Tolerations come in to use?

Answer 2

• when we have nodes with certain resources meant for applications with certain needs

Question 3

What kind of tolerations are default for pods?

Answer 3

no tolerations

Question 4

What kind of tolerations exist?

Answer 4

• intolerant
• tolerant

Question 5

If we apply a taint Blue to a node, what does that mean for pods to be scheduled?

Answer 5

• by default pods have no tolerations, therefore they cannot use the tainted node
• only pods with a toleration to blue, would be able to be scheduled there

Question 6

Where are Taints / Tolerations set?

Answer 6

Taints = nodes

Tolerations = pods

Question 7

How do we taint a node?

Answer 7

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

i.e.
kubectl taint nodes control-plane app=blue:NoSchedule
-> applies a blue taint

taint-effect = what happens to pods, that DO NO Tolerate this taint

Question 8

What does the taint-effect do?

Answer 8

Specifies what happens to pods, that don’t tolerate the taint

Question 9

What taint-effects exist?

Answer 9

• NoSchedule -> pods will not be scheduled on node
• PreferNoSchedule -> system will try to avoid placing pod on node, but not guaranteed
• NoExecute -> pods not scheduled and existing pods on the node will be evicted if they do not tolerate the taint

Question 10

How do we apply Tolerations to a pod? I.e for a tainted node with:

‘kubectl taint nodes control-plane app=blue:NoSchedule’

Answer 10

pod-yaml:

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

Question 11

Is a tolerant pod able to be scheduled on other nodes as well?

Answer 11

Yes. It can be scheduled on nodes, where it is Tolerant of the taint as well as nodes without Taint

Question 12

How can you find out if a node is tainted or not?

Answer 12

kubectl describe node node-name | grep Taint