> ## 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.
# Manual Scheduling
> This guide explains how to assign pods to nodes without relying on Kubernetes’ built-in scheduler for tighter control over pod placement.
Welcome to this lesson on manually scheduling pods in Kubernetes. This guide explains how to assign pods to nodes without relying on Kubernetes’ built-in scheduler. Manual scheduling can be useful in niche scenarios where you need tighter control over pod placement. In this article, we review a basic pod manifest, demonstrate how manual scheduling works, and show you how to use binding objects to reassign pods if necessary.
## Understanding the Default Scheduler Behavior
Every pod definition includes a field called `nodeName`, which is left unset by default. The Kubernetes scheduler automatically scans for pods without a `nodeName` and selects an appropriate node by updating this field and creating a binding object. Consider the basic pod manifest below:
```yaml theme={null}
apiVersion: v1
kind: Pod
metadata:
name: nginx
labels:
name: nginx
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 8080
```
Typically, you do not include the `nodeName` field in your manifest. The scheduler uses this field only after selecting a node for the pod.
## Manually Setting the Node Name
To manually assign a pod to a specific node during creation, populate the `nodeName` field in the manifest. For example, to schedule the pod on a node called "node02", update your manifest as follows:
```yaml theme={null}
apiVersion: v1
kind: Pod
metadata:
name: nginx
labels:
name: nginx
spec:
nodeName: node02
containers:
- name: nginx
image: nginx
ports:
- containerPort: 8080
```
After creating the pod with this manifest, check its status with:
```bash theme={null}
kubectl get pods
```
Sample output before the scheduler assigns the IP:
```bash theme={null}
NAME READY STATUS RESTARTS AGE
nginx 0/1 Pending 0 3s
```
And after the pod becomes ready:
```bash theme={null}
kubectl get pods
NAME READY STATUS RESTARTS AGE IP NODE
nginx 1/1 Running 0 9s 10.40.0.4 node02
```
The `nodeName` must be set during pod creation. Once the pod is running, Kubernetes does not permit modifications to the `nodeName` field.
## Reassigning a Running Pod Using a Binding Object
If a pod is already running and you need to change its node assignment, you cannot modify its `nodeName` directly. In this scenario, you can create a binding object that mimics the scheduler’s behavior.
1. Create a binding object that specifies the target node ("node02"):
```yaml theme={null}
apiVersion: v1
kind: Binding
metadata:
name: nginx
target:
apiVersion: v1
kind: Node
name: node02
```
2. The original pod definition remains unchanged:
```yaml theme={null}
apiVersion: v1
kind: Pod
metadata:
name: nginx
labels:
name: nginx
spec:
containers:
- name: nginx
image: nginx
ports:
- containerPort: 8080
```
3. Convert the YAML binding to JSON (e.g., save it as `binding.json`) and send a POST request to the pod’s binding API using curl:
```bash theme={null}
curl --header "Content-Type: application/json" --request POST --data @binding.json http://$SERVER/api/v1/namespaces/default/pods/nginx/binding
```
This binding instructs Kubernetes to assign the existing pod to the specified node without altering its original manifest.
## Quick Reference Table
| Method | Use Case | Example Snippet Reference |
| ---------------------- | ---------------------------------- | ------------------------------------ |
| Direct Assignment | Set `nodeName` during pod creation | See manifest with `nodeName: node02` |
| Using a Binding Object | Reassign a running pod | See binding object example |
## Additional Resources
* [Kubernetes Basics](https://kubernetes.io/docs/concepts/overview/what-is-kubernetes/)
* [Kubernetes Documentation](https://kubernetes.io/docs/)
That’s it for this lesson. Experiment with manually scheduling pods to solidify your understanding of Kubernetes node assignments. Happy scheduling!