Use context: kubectl config use-context k8s-c2-AC

Ssh into the controlplane node with ssh cluster2-controlplane1. Temporarily stop the kube-scheduler, this means in a way that you can start it again afterwards.

Create a single Pod named manual-schedule of image httpd:2.4-alpine, confirm it’s created but not scheduled on any node.

Now you’re the scheduler and have all its power, manually schedule that Pod on node cluster2-controlplane1. Make sure it’s running.

Start the kube-scheduler again and confirm it’s running correctly by creating a second Pod named manual-schedule2 of image httpd:2.4-alpine and check if it’s running on cluster2-node1.

Manually Scheduling a Kubernetes Pod by Stopping the Scheduler

In this guide, we’ll explore how to manually schedule a Kubernetes Pod by temporarily stopping the Kubernetes scheduler. This exercise will give you a deeper understanding of how the scheduler works and how Pods are assigned to nodes.

Step 1: Stop the Scheduler

First, we need to identify the control plane node where the scheduler is running. Use the following command to list the nodes:

Next, SSH into the control plane node and check if the scheduler is running:

To stop the scheduler, move the scheduler’s manifest file out of the manifests directory:

Verify that the scheduler has stopped:

Step 2: Create a Pod

With the scheduler stopped, create a Pod using the following command:

Check that the Pod has no node assigned:

Step 3: Manually Schedule the Pod

To manually schedule the Pod, download its YAML definition and edit it to specify the node name:

Edit the 9.yaml file to include the node name:

Since you cannot use kubectl apply or kubectl edit for this, you’ll need to replace the Pod:

Check if the Pod is now running on the control plane node:

Step 4: Restart the Scheduler

After manually scheduling the Pod, restart the scheduler by moving the manifest file back to its original location:

Verify that the scheduler is running again:

Step 5: Create a Second Test Pod

To confirm that the scheduler is working normally again, create another Pod:

Check where both Pods are running:

Everything is back to normal, with the scheduler automatically assigning the second Pod to a node.

In this exercise, we manually scheduled a Kubernetes Pod by temporarily disabling the scheduler, showing how the scheduler assigns Pods to nodes and how you can intervene in this process if necessary.