$ kubectl describe node node01 | grep -A 5 -i label
Labels: beta.kubernetes.io/arch=amd64
beta.kubernetes.io/os=linux
kubernetes.io/arch=amd64
kubernetes.io/hostname=node01
kubernetes.io/os=linux
Annotations: flannel.alpha.coreos.com/backend-data: null
$ kubectl get nodes --show-labels | grep node01
node01 Ready <none> 6m53s v1.19.0 beta.kubernetes.io/arch=amd64,beta.kubernetes.io/os=linux,kubernetes.io/arch=amd64,kubernetes.io/hostname=node01,kubernetes.io/os=linux$ kubectl label node node01 color=blue
node/node01 labeled$ kubectl create deployment --image=nginx blue
deployment.apps/blue created
$ kubectl scale deployment blue --replicas=6
deployment.apps/blue scaled$ kubectl get pods --show-labels | grep "app=blue"
blue-7bb46df96d-56t7b 1/1 Running 0 4m8s app=blue,pod-template-hash=7bb46df96d
blue-7bb46df96d-cjjdm 1/1 Running 0 4m14s app=blue,pod-template-hash=7bb46df96d
blue-7bb46df96d-f78p2 1/1 Running 0 4m7s app=blue,pod-template-hash=7bb46df96d
blue-7bb46df96d-fwzv8 1/1 Running 0 4m8s app=blue,pod-template-hash=7bb46df96d
blue-7bb46df96d-g8dcv 1/1 Running 0 4m8s app=blue,pod-template-hash=7bb46df96d
blue-7bb46df96d-qf5sq 1/1 Running 0 4m8s app=blue,pod-template-hash=7bb46df96d
$ kubectl get nodes --show-labels | grep "app=blue" | wc -l
0
$ kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
blue-7bb46df96d-56t7b 1/1 Running 0 5m44s 10.244.0.6 controlplane <none> <none>
blue-7bb46df96d-cjjdm 1/1 Running 0 5m50s 10.244.1.3 node01 <none> <none>
blue-7bb46df96d-f78p2 1/1 Running 0 5m43s 10.244.1.6 node01 <none> <none>
blue-7bb46df96d-fwzv8 1/1 Running 0 5m44s 10.244.1.4 node01 <none> <none>
blue-7bb46df96d-g8dcv 1/1 Running 0 5m44s 10.244.1.5 node01 <none> <none>
blue-7bb46df96d-qf5sq 1/1 Running 0 5m44s 10.244.0.7 controlplane <none> <none>-
Name: blue
-
Replicas: 6
-
Image: nginx
-
NodeAffinity: requiredDuringSchedulingIgnoredDuringExecution
-
Key: color
-
values: blue
-
Create the deployment file
$ kubectl get deployment blue -o yaml > blue.yaml- Now add the following to the deployment file
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: color
operator: In
values:
- blue- Apply the changes
$ kubectl apply -f blue.yaml
deployment.apps/blue configure- What we changed
$ cat blue.yaml | grep -A 10 spec:
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: color
operator: In
values:
- blue
containers:- Now check the node affinity of the blue deployment pods
$ kubectl get pods -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
blue-566c768bd6-77zfz 1/1 Running 0 76s 10.244.1.7 node01 <none> <none>
blue-566c768bd6-9rrqn 1/1 Running 0 71s 10.244.1.11 node01 <none> <none>
blue-566c768bd6-mtndx 1/1 Running 0 76s 10.244.1.9 node01 <none> <none>
blue-566c768bd6-nqb9n 1/1 Running 0 76s 10.244.1.8 node01 <none> <none>
blue-566c768bd6-tllbv 1/1 Running 0 73s 10.244.1.10 node01 <none> <none>
blue-566c768bd6-wmgnh 1/1 Running 0 71s 10.244.1.12 node01 <none> <none>Create a new deployment named red with the nginx image and 3 replicas, and ensure it gets placed on the master/controlplane node only.
-
Name: red
-
Replicas: 3
-
Image: nginx
-
NodeAffinity: requiredDuringSchedulingIgnoredDuringExecution
-
Key: node-role.kubernetes.io/master
-
Use the Exists operator
-
Create the deployment
$ kubectl create deployment red --image=nginx
deployment.apps/red created- Scale the deployment
$ kubectl scale deployment red --replicas=3
deployment.apps/red scaled- Get deployment
$ kubectl get deployment red -o yaml > red.yaml- Apply a label color=red to node controlplane
$ kubectl label node controlplane color=red
node/controlplane labeled- Now add the following to the deployment file
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: color
operator: In
values:
- red- Now check the red pods
$ kubectl get pods -o wide | grep red
red-6869b66f86-8n8nk 1/1 Running 0 6m2s 10.244.0.7 controlplane <none> <none>
red-6869b66f86-8p9gj 1/1 Running 0 5m59s 10.244.0.8 controlplane <none> <none>
red-6869b66f86-zs2qq 1/1 Running 0 6m5s 10.244.0.6 controlplane <none> <none>-
We could have achieved the same thing using the following key-value pair as well
- Key: node-role.kubernetes.io/master
- Use the Exists operator
-
So add the following to yaml file
- Now add the following to the deployment file
```yaml
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: color
operator: In
values:
- red
- key: node-role.kubernetes.io/master
operator: Exists- Now try applying the changes again. You will get the following error
for: "red.yaml": Operation cannot be fulfilled on deployments.apps "red": the object has been modified; please apply your changes to the latest version and try again- This is because we didn't create the yaml file again from the latest version of object
$ kubectl get deployment red -o yaml > red.yaml- Now adding the following to yaml part to
red.yaml
spec:
affinity:
nodeAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
nodeSelectorTerms:
- matchExpressions:
- key: color
operator: In
values:
- red
- key: node-role.kubernetes.io/master
operator: Exists- And applying the changes
$ kubectl apply -f red.yamldeployment.apps/red configured