> ## 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 Multiple Scheduler > Guide to deploy and configure an additional Kubernetes scheduler, create its ConfigMap and RBAC, run a scheduler Pod, and verify scheduling of a test Pod. In this lesson you'll practice deploying an additional Kubernetes scheduler alongside the cluster's default scheduler. Follow each step to inspect the running scheduler, create configuration and RBAC resources, deploy a second scheduler Pod, and verify a test Pod is scheduled by the new scheduler. Goal summary: * Inspect the default kube-scheduler Pod to determine the image in use. * Create a ConfigMap containing the scheduler configuration. * Deploy an additional scheduler Pod that uses the same scheduler image. * Create a test Pod that is scheduled by the new scheduler. | Step | Task | Key command / resource | | - | - | - | | 1 | Inspect default kube-scheduler and identify its image | `kubectl describe pod -n kube-system \| grep Image` | | 2 | Verify service account / RBAC for the custom scheduler | `kubectl get sa my-scheduler -n kube-system` | | 3 | Create ConfigMap from scheduler config file | `kubectl create configmap my-scheduler-config --from-file=/root/my-scheduler-config.yaml -n kube-system` | | 4 | Edit Pod manifest and set `image` to match the control-plane scheduler | `/root/my-scheduler.yaml` (update `image`) | | 5 | Create the new scheduler Pod | `kubectl create -f /root/my-scheduler.yaml` | | 6 | Create a test Pod using `schedulerName: my-scheduler` | `kubectl create -f /root/nginx-pod.yaml` | *** ## 1) Inspect the default scheduler Pod and identify its image First, list Pods in the `kube-system` namespace and locate the kube-scheduler Pod: ```bash theme={null} kubectl get pods -n kube-system ``` Identify the specific kube-scheduler Pod name from that list, then describe it to find the image in use. Example (replace the pod name if different in your cluster): ```bash theme={null} kubectl describe pod kube-scheduler-controlplane -n kube-system | grep Image ``` Example output (this shows the exact image string you should use for the custom scheduler): ```text theme={null} Image: k8s.gcr.io/kube-scheduler:v1.23.0 Image ID: docker-pullable://k8s.gcr.io/kube-scheduler@sha256:af8166ce28baa7cb902a2c0d16da865d5d7c892fe1b41187fd4be78ec6291c23 ``` Always use the exact image string shown by the running kube-scheduler (including the tag) when configuring your custom scheduler Pod (for example, `k8s.gcr.io/kube-scheduler:v1.23.0`). This ensures compatibility between scheduler binary and cluster components. *** ## 2) Verify service account / RBAC are present The lab environment includes a service account and ClusterRoleBinding for the custom scheduler. Confirm the service account exists: ```bash theme={null} kubectl get sa my-scheduler -n kube-system ``` Expected output: ```text theme={null} NAME SECRETS AGE my-scheduler 1 26s ``` If you need to inspect or troubleshoot RBAC, list role bindings and cluster role bindings: ```bash theme={null} kubectl get clusterrolebinding | grep my-scheduler kubectl get rolebinding -n kube-system | grep my-scheduler ``` If the custom scheduler lacks the necessary RBAC (ClusterRole / ClusterRoleBinding), it will be unable to communicate with the API server and schedule Pods. Ensure the service account has appropriate permissions. *** ## 3) Create a ConfigMap for the scheduler configuration A scheduler configuration file is provided at `/root/my-scheduler-config.yaml`. Create a ConfigMap named `my-scheduler-config` in the `kube-system` namespace from that file: ```bash theme={null} kubectl create configmap my-scheduler-config --from-file=/root/my-scheduler-config.yaml -n kube-system ``` Verify the ConfigMap was created: ```bash theme={null} kubectl get configmap my-scheduler-config -n kube-system ``` Expected output: ```text theme={null} NAME DATA AGE my-scheduler-config 1 17s ``` For reference, the scheduler configuration file might look like this: ```yaml theme={null} apiVersion: kubescheduler.config.k8s.io/v1beta2 kind: KubeSchedulerConfiguration profiles: - schedulerName: my-scheduler leaderElection: leaderElect: false ``` This configuration sets a custom scheduler profile named `my-scheduler`. `leaderElect: false` is often used for single-instance scheduler testing; in production you typically enable leader election for HA setups. *** ## 4) Prepare the Pod manifest for the additional scheduler A Pod manifest is provided at `/root/my-scheduler.yaml`. It contains the container command, liveness/readiness probes, the volume mount for the ConfigMap, and essential spec fields. Open the file and update the container `image` field to match the image discovered in step 1 (for example `k8s.gcr.io/kube-scheduler:v1.23.0`). Example snippet (ensure you replace the `image:` line with the exact image string found earlier): ```yaml theme={null} kind: Pod metadata: labels: run: my-scheduler name: my-scheduler namespace: kube-system spec: serviceAccountName: my-scheduler containers: - command: - /usr/local/bin/kube-scheduler - --config=/etc/kubernetes/my-scheduler/my-scheduler-config.yaml image: k8s.gcr.io/kube-scheduler:v1.23.0 livenessProbe: httpGet: path: /healthz port: 10259 scheme: HTTPS initialDelaySeconds: 15 name: kube-second-scheduler readinessProbe: httpGet: path: /healthz port: 10259 scheme: HTTPS resources: requests: cpu: '0.1' securityContext: privileged: false volumeMounts: - name: config-volume mountPath: /etc/kubernetes/my-scheduler hostNetwork: false hostPID: false volumes: - name: config-volume configMap: name: my-scheduler-config ``` Note: do not include any angle-bracket placeholders in the `image` field. Use the literal image tag from step 1. *** ## 5) Create the new scheduler Pod Apply the manifest to create the Pod in the cluster: ```bash theme={null} kubectl create -f /root/my-scheduler.yaml ``` Expected response: ```text theme={null} pod/my-scheduler created ``` Verify the new scheduler Pod appears and becomes ready in the `kube-system` namespace: ```bash theme={null} kubectl get pods -n kube-system ``` Example output showing the custom scheduler running: ```text theme={null} NAME READY STATUS RESTARTS AGE coredns-64897985d-6qwf5 1/1 Running 0 11m coredns-64897985d-9rdt8 1/1 Running 0 11m etcd-controlplane 1/1 Running 0 11m kube-apiserver-controlplane 1/1 Running 0 11m kube-controller-manager-controlplane 1/1 Running 0 11m kube-flannel-ds-rl72v 1/1 Running 0 11m kube-proxy-tzwkm 1/1 Running 0 11m kube-scheduler-controlplane 1/1 Running 0 11m my-scheduler 1/1 Running 0 7s ``` If the Pod remains in `CrashLoopBackOff` or `Pending`, describe the Pod for diagnostics: ```bash theme={null} kubectl describe pod my-scheduler -n kube-system kubectl logs my-scheduler -n kube-system ``` Look for probe failures, permission errors, or config file mounting issues. *** ## 6) Create a test Pod that uses the custom scheduler A test Pod manifest is provided at `/root/nginx-pod.yaml`. By default it looks like: ```yaml theme={null} apiVersion: v1 kind: Pod metadata: name: nginx spec: containers: - image: nginx name: nginx ``` To ensure this Pod is scheduled by your new scheduler, add the `schedulerName` field with the value `my-scheduler`: ```yaml theme={null} apiVersion: v1 kind: Pod metadata: name: nginx spec: schedulerName: my-scheduler containers: - image: nginx name: nginx ``` Create the Pod: ```bash theme={null} kubectl create -f /root/nginx-pod.yaml ``` Confirm the Pod is scheduled and running: ```bash theme={null} kubectl get pod nginx ``` Example output when the Pod is running: ```text theme={null} NAME READY STATUS RESTARTS AGE nginx 1/1 Running 0 10s ``` If the Pod is not scheduled, inspect it for events and errors: ```bash theme={null} kubectl describe pod nginx ``` In the `Events` section, look for scheduling attempts and any errors returned by `my-scheduler`. If no scheduling attempts are recorded, verify the custom scheduler Pod is running and communicating with the API server. *** That completes the steps to add an additional scheduler to the cluster and schedule a Pod using it. ## Links and References * [Kubernetes Scheduler Overview](https://kubernetes.io/docs/concepts/scheduling-eviction/kube-scheduler/) * [Kube-scheduler Configuration](https://kubernetes.io/docs/reference/config-api/kube-scheduler-config.v1/) * [RBAC Authorization](https://kubernetes.io/docs/reference/access-authn-authz/rbac/) * [kubectl Cheat Sheet](https://kubernetes.io/docs/reference/kubectl/cheatsheet/) This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.