> ## 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.
# Solution Multiple Scheduler
> Learn to deploy multiple schedulers in Kubernetes, including identifying the default scheduler and creating a custom scheduler configuration.
In this lesson, you will learn how to deploy multiple schedulers in Kubernetes. We will go through the steps to identify the default scheduler, create and deploy a custom scheduler configuration, and finally run a pod using the new scheduler.
***
## 1. Identify the Default Scheduler
Begin by inspecting the cluster's pods to identify the default Kubernetes scheduler pod. In most installations, the pod name is similar to `kube-scheduler-controlplane`. Use the following command to list all pods across namespaces:
```bash theme={null}
root@controlplane ~ ⟩ kubectl get pods -A
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system coordns-64897985d-6qwf5 1/1 Running 0 6m14s
kube-system coordns-64897985d-9rdt8 1/1 Running 0 6m14s
kube-system etcd-controlplane 1/1 Running 0 6m25s
kube-system kube-apiserver-controlplane 1/1 Running 0 6m30s
kube-system kube-controller-manager-controlplane 1/1 Running 0 6m14s
kube-system kube-proxy-tzkwm 1/1 Running 0 6m14s
kube-system kube-scheduler-controlplane 1/1 Running 0 6m25s
root@controlplane ~ ⟩
```
Next, determine the image used by the default scheduler. Describe the scheduler pod in the `kube-system` namespace:
```bash theme={null}
kubectl describe pod kube-scheduler-controlplane -n kube-system
```
In the description output, look for an entry similar to:
```text theme={null}
Image: k8s.gcr.io/kube-scheduler:v1.23.0
```
This image will be necessary when configuring your custom scheduler.
***
## 2. Verify Service Account and Cluster Role Binding
Before deploying the custom scheduler, ensure that the service account and cluster role binding required for it are in place. Verify the service account with the following commands:
```bash theme={null}
root@controlplane ~ ⊢ kubectl get sa my-scheduler
Error from server (NotFound): serviceaccounts "my-scheduler" not found
root@controlplane ~ ⊢ kubectl get sa my-scheduler -n kube-system
NAME SECRETS AGE
my-scheduler 1 26s
```
Since the necessary resources exist, you can proceed to the next step.
***
## 3. Create a ConfigMap for the Custom Scheduler Configuration
Create a configuration file for the custom scheduler at `/root/my-scheduler-config.yaml` with the following content:
```yaml theme={null}
apiVersion: kubescheduler.config.k8s.io/v1beta2
kind: KubeSchedulerConfiguration
profiles:
- schedulerName: my-scheduler
leaderElection:
leaderElect: false
```
You can verify the file content using:
```bash theme={null}
root@controlplane ~ ✗ cat /root/my-scheduler-config.yaml
apiVersion: kubescheduler.config.k8s.io/v1beta2
kind: KubeSchedulerConfiguration
profiles:
- schedulerName: my-scheduler
leaderElection:
leaderElect: false
```
Now, create a ConfigMap from this file in the `kube-system` namespace. Note that the correct flag is used rather than `--name`:
```bash theme={null}
root@controlplane ~ ✗ kubectl create configmap my-scheduler-config --from-file=/root/my-scheduler-config.yaml -n kube-system
configmap/my-scheduler-config created
```
Verify that the ConfigMap was created successfully:
```bash theme={null}
root@controlplane ~ ✗ kubectl get configmap my-scheduler-config -n kube-system
NAME DATA AGE
my-scheduler-config 1 17s
```
Ensure that the ConfigMap is correctly created and mounted to avoid configuration issues with your custom scheduler.
***
## 4. Deploy the Custom Scheduler
Deploy the custom scheduler using a manifest file (e.g., `/root/my-scheduler.yaml`). The manifest below deploys a custom scheduler pod using the same image as the default scheduler. Replace `` with `k8s.gcr.io/kube-scheduler:v1.23.0` as shown:
```yaml theme={null}
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
```
Deploy the custom scheduler by running:
```bash theme={null}
root@controlplane ~ ⛰ kubectl create -f my-scheduler.yaml
pod/my-scheduler created
```
After deployment, confirm that all pods in the `kube-system` namespace are running as expected:
```bash theme={null}
root@controlplane ~ ⛰ kubectl get pods -n kube-system
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
```
Always verify your deployment by checking the pod status, ensuring that no critical errors persist.
***
## 5. Create a Pod Using the Custom Scheduler
The final step involves creating a pod that explicitly uses the newly deployed custom scheduler. Below is an example manifest for an nginx pod. Notice that we specify `schedulerName: my-scheduler` to bind the pod to the custom scheduler:
```yaml theme={null}
apiVersion: v1
kind: Pod
metadata:
name: nginx
spec:
schedulerName: my-scheduler
containers:
- image: nginx
name: nginx
```
Save this manifest to a file named `nginx-pod.yaml`, then create the pod:
```bash theme={null}
root@controlplane ~ # kubectl create -f nginx-pod.yaml
pod/nginx created
```
Confirm that the pod is running as expected in the default namespace (or your desired namespace):
```bash theme={null}
root@controlplane ~ # kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx 1/1 Running 0 4s
```
***
This completes the lab for deploying a custom scheduler in Kubernetes and scheduling a pod using that scheduler.
For more detailed information on Kubernetes scheduling, please check out the [Kubernetes Documentation](https://kubernetes.io/docs/).