> ## Documentation Index > Fetch the complete documentation index at: https://notes.kodekloud.com/llms.txt > Use this file to discover all available pages before exploring further. # Lab Solution Node Affinity Optional > A hands-on Kubernetes lab demonstrating inspecting and labeling nodes, creating deployments, and using nodeAffinity rules to constrain pods with In and Exists operators This lab walks through practical Kubernetes node affinity tasks: inspecting node labels, labeling a node, creating deployments, and constraining pods to specific nodes using nodeAffinity. The steps below show the commands, minimal YAML snippets, and verification commands you can run in a cluster. *** ## 1) Count labels on node01 List labels on a node with either `kubectl describe` or `kubectl get --show-labels`. Example using `--show-labels`: ```bash theme={null} root@controlplane:~# kubectl get node node01 --show-labels NAME STATUS ROLES AGE VERSION LABELS node01 Ready 14m v1.20.0 beta.kubernetes.io/arch=amd64,kubernetes.io/hostname=node01,... ``` Or view the full label list with: ```bash theme={null} root@controlplane:~# kubectl describe node node01 # Look under the "Labels:" section in the output. ``` Count the labels shown. (In the environment used here the node shows six labels.) *** ## 2) Check the value of `beta.kubernetes.io/arch` on node01 You can scan the `--show-labels` output for the label or inspect `kubectl describe` output: ```bash theme={null} root@controlplane:~# kubectl get node node01 --show-labels # Look for the 'beta.kubernetes.io/arch' label in the LABELS column. ``` In this cluster `beta.kubernetes.io/arch=amd64`. *** ## 3) Apply a label `color=blue` to node01 Add a label to the node using `kubectl label`: ```bash theme={null} root@controlplane:~# kubectl label node node01 color=blue node/node01 labeled ``` Verify the label was applied: ```bash theme={null} root@controlplane:~# kubectl get node node01 --show-labels NAME STATUS ROLES AGE VERSION LABELS node01 Ready 14m v1.20.0 color=blue,beta.kubernetes.io/arch=amd64,... ``` *** ## 4) Create a deployment named `blue` (nginx) with 3 replicas Create the deployment: ```bash theme={null} root@controlplane:~# kubectl create deployment blue --image=nginx --replicas=3 deployment.apps/blue created ``` Before adding affinity, check which nodes could schedule the pods. Look for taints (if no taints, pods may schedule to any node that meets resource/constraint requirements): ```bash theme={null} root@controlplane:~# kubectl get nodes NAME STATUS ROLES AGE VERSION controlplane Ready control-plane,master 15m v1.20.0 node01 Ready 14m v1.20.0 root@controlplane:~# kubectl describe node node01 | grep Taints Taints: root@controlplane:~# kubectl describe node controlplane | grep Taints Taints: ``` Because there are no taints, the scheduler could place the `blue` pods on either node by default. *** ## 5) Constrain `blue` deployment to node01 using nodeAffinity Edit the `blue` Deployment and add a nodeAffinity rule under `spec.template.spec.affinity.nodeAffinity` so the scheduler only places pods on nodes with `color=blue`. Open the deployment for editing: ```bash theme={null} root@controlplane:~# kubectl edit deployment blue ``` Inside the Deployment's Pod template, add the following YAML under `spec.template.spec` (maintain correct indentation relative to the existing manifest): ```yaml theme={null} affinity: nodeAffinity: requiredDuringSchedulingIgnoredDuringExecution: nodeSelectorTerms: - matchExpressions: - key: color operator: In values: - blue ``` A minimal view of the relevant part of the updated Deployment spec: ```yaml theme={null} spec: replicas: 3 template: metadata: labels: app: blue spec: affinity: nodeAffinity: requiredDuringSchedulingIgnoredDuringExecution: nodeSelectorTerms: - matchExpressions: - key: color operator: In values: - blue containers: - name: nginx image: nginx ``` Save the edit and verify the pods are scheduled on `node01`: ```bash theme={null} root@controlplane:~# kubectl get pods -o wide -l app=blue NAME READY STATUS RESTARTS AGE NODE blue-xxxxx-yyyyy 1/1 Running 0 1m node01 blue-xxxxx-zzzzz 1/1 Running 0 1m node01 blue-xxxxx-aaaaa 1/1 Running 0 1m node01 ``` All `blue` pods are now placed on `node01` as required. When using `operator: In` you must provide one or more `values`. The node must have the exact label key/value pair to match. *** ## 6) Create a deployment named `red` (nginx) with 2 replicas and ensure it runs on the control plane node The control plane node has the label `node-role.kubernetes.io/master` (no value). To match nodes that have the label regardless of its value, use the `Exists` operator. Recommended workflow: generate the Deployment YAML with a dry-run, edit it to add the affinity block, then create it. Generate YAML: ```bash theme={null} root@controlplane:~# kubectl create deployment red --image=nginx --replicas=2 --dry-run=client -o yaml > red.yaml ``` Edit `red.yaml` and add the nodeAffinity under `spec.template.spec`: ```yaml theme={null} spec: replicas: 2 template: metadata: labels: app: red spec: affinity: nodeAffinity: requiredDuringSchedulingIgnoredDuringExecution: nodeSelectorTerms: - matchExpressions: - key: node-role.kubernetes.io/master operator: Exists containers: - name: nginx image: nginx ``` Important: `operator: Exists` must be used without a `values` field. Create the deployment: ```bash theme={null} root@controlplane:~# kubectl create -f red.yaml deployment.apps/red created ``` Verify the `red` pods are scheduled on the control plane node: ```bash theme={null} root@controlplane:~# kubectl get pods -o wide -l app=red NAME READY STATUS RESTARTS AGE NODE red-xxxxx-yyyyy 1/1 Running 0 30s controlplane red-xxxxx-zzzzz 1/1 Running 0 30s controlplane ``` YAML indentation is significant. If you see errors like `did not find expected key` when creating from a file, check the spacing/indentation for the added affinity block relative to `spec.template.spec`. *** ## Quick reference: common commands and affinity operators | Purpose | Command / YAML | | - | - | | List node labels | `kubectl get node node01 --show-labels` | | Describe node | `kubectl describe node node01` | | Add a label to a node | `kubectl label node node01 color=blue` | | Create deployment | `kubectl create deployment blue --image=nginx --replicas=3` | | Dry-run to file | `kubectl create deployment red --image=nginx --replicas=2 --dry-run=client -o yaml > red.yaml` | | nodeAffinity key exists (no value) | `operator: Exists` | | nodeAffinity exact match | `operator: In` with `values: ["blue"]` | *** You have now completed the lab tasks: * inspected node labels, * applied a node label, * created a deployment and constrained it to a specific node using nodeAffinity with `In`, * and created another deployment constrained to nodes that have a label using the `Exists` operator. ## Links and References * [Kubernetes Node Affinity documentation](https://kubernetes.io/docs/concepts/scheduling-eviction/assign-pod-node/#node-affinity) * [kubectl cheat sheet](https://kubernetes.io/docs/reference/kubectl/cheatsheet/) * [Kubernetes scheduling concepts](https://kubernetes.io/docs/concepts/scheduling-eviction/) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.