> ## 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 Manual Scheduling optional > Hands-on lab showing how to diagnose a Pending Kubernetes Pod when kube-scheduler is absent and manually schedule it to a node by setting nodeName In this lab you will diagnose a Pending Pod caused by a missing scheduler and manually schedule it onto a specific node using `nodeName`. This exercise demonstrates how Kubernetes schedules Pods, what happens when the scheduler is not available, and how to place a Pod on a chosen node manually. Objective: create a Pod from `nginx.yaml` and manually schedule it onto specific nodes when the kube-scheduler is not available. *** ## Initial environment and Pod creation Environment summary: * Cluster with two nodes (controlplane and node01). * A file named `nginx.yaml` defines a simple Pod using the `nginx` image. * We'll create the Pod and observe its status. Check nodes and list files: ```shell theme={null} root@controlplane:~# kubectl get nodes NAME STATUS ROLES AGE VERSION controlplane Ready control-plane,master 14m v1.20.0 node01 Ready 14m v1.20.0 root@controlplane:~# ls nginx.yaml sample.yaml ``` Contents of `nginx.yaml` (initial version): ```yaml theme={null} --- apiVersion: v1 kind: Pod metadata: name: nginx spec: containers: - image: nginx name: nginx ``` Create the Pod: ```shell theme={null} root@controlplane:~# kubectl create -f nginx.yaml pod/nginx created ``` *** ## Check Pod status Immediately after creation the Pod appears in Pending state: ```shell theme={null} root@controlplane:~# kubectl get pods NAME READY STATUS RESTARTS AGE nginx 0/1 Pending 0 12s ``` *** ## Why is the Pod Pending? A Pending Pod typically means it has not been scheduled to any node. Inspecting the Pod shows `Node: ` and there are no scheduling events: ```shell theme={null} root@controlplane:~# kubectl describe pod nginx Name: nginx Namespace: default Priority: 0 Node: Labels: Annotations: Status: Pending IP: IPs: Containers: nginx: Image: nginx Port: Host Port: Environment: Mounts: /var/run/secrets/kubernetes.io/serviceaccount from default-token-kpdm6 (ro) Volumes: default-token-kpdm6: Type: Secret (a volume populated by a Secret) SecretName: default-token-kpdm6 Optional: false QoS Class: BestEffort Node-Selectors: Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s node.kubernetes.io/unreachable:NoExecute op=Exists for 300s Events: ``` Check core control-plane Pods in the `kube-system` namespace: ```shell theme={null} root@controlplane:~# kubectl get pods -n kube-system NAME READY STATUS RESTARTS AGE coredns-74ff55c5b-csz5x 1/1 Running 0 16m coredns-74ff55c5b-vzlnv 1/1 Running 0 16m etcd-controlplane 1/1 Running 0 16m kube-apiserver-controlplane 1/1 Running 0 16m kube-controller-manager-controlplane 1/1 Running 0 16m kube-flannel-ds-9pcnm 1/1 Running 0 16m kube-flannel-ds-nzbns 1/1 Running 0 16m # Note: There is no kube-scheduler Pod listed here. ``` Because the scheduler Pod (`kube-scheduler`) is not present, no automated scheduling occurs and the Pod remains in the Pending state. *** ## Manually scheduling the Pod You can bypass the kube-scheduler by setting `nodeName` in the Pod spec. This pins the Pod to the named node during creation. Edit `nginx.yaml` and add `nodeName: node01` under `spec`: ```yaml theme={null} --- apiVersion: v1 kind: Pod metadata: name: nginx spec: nodeName: node01 containers: - image: nginx name: nginx ``` Apply the change by replacing the existing Pod. `kubectl replace --force -f` deletes and recreates the resource: ```shell theme={null} root@controlplane:~# kubectl replace --force -f nginx.yaml pod "nginx" deleted pod/nginx replaced ``` Monitor the Pod as it is being created (it typically moves from `ContainerCreating` to `Running`): ```shell theme={null} root@controlplane:~# kubectl get pods NAME READY STATUS RESTARTS AGE nginx 0/1 ContainerCreating 0 8s root@controlplane:~# kubectl get pods --watch NAME READY STATUS RESTARTS AGE nginx 1/1 Running 0 19s ``` Verify which node the Pod landed on using wide output: ```shell theme={null} root@controlplane:~# kubectl get pods -o wide NAME READY STATUS RESTARTS AGE IP NODE nginx 1/1 Running 0 1m 10.244.1.2 node01 ``` *** You cannot move a running Pod from one node to another directly. To "move" a Pod, delete the Pod on its current node and recreate it with a different `nodeName` (or let the kube-scheduler place it). Pods are host-bound until recreated elsewhere. Deleting a Pod includes a graceful termination period: Kubernetes sends termination signals to the container and waits for shutdown. This can take a few seconds and is expected behavior. *** ## Scheduling the Pod on the control-plane node For practice, set `nodeName: controlplane` in `nginx.yaml` and repeat the replace step. This forces the Pod onto the control-plane node even if the scheduler would not place regular workloads there. Important: control-plane nodes often include taints (for example, `node-role.kubernetes.io/master:NoSchedule`) that prevent regular workloads from being scheduled. Manually setting `nodeName` bypasses the scheduler, but NoExecute taints can still evict a Pod unless it has matching tolerations. Example replace & watch commands: ```shell theme={null} # Edit nginx.yaml to set nodeName: controlplane, then: kubectl replace --force -f nginx.yaml kubectl get pods -o wide --watch ``` *** ## Quick command reference | Task | Command / Example | | - | - | | View nodes | `kubectl get nodes` | | Create a Pod from a file | `kubectl create -f nginx.yaml` | | Replace (force) a resource | `kubectl replace --force -f nginx.yaml` | | Describe a Pod | `kubectl describe pod nginx` | | Watch Pod status | `kubectl get pods --watch` | | Show Pod with node info | `kubectl get pods -o wide` | | List kube-system Pods | `kubectl get pods -n kube-system` | *** ## Links and references * Kubernetes documentation: [https://kubernetes.io/docs/](https://kubernetes.io/docs/) * Scheduling in Kubernetes (concepts): [https://kubernetes.io/docs/concepts/scheduling-eviction/](https://kubernetes.io/docs/concepts/scheduling-eviction/) * Taints and tolerations: [https://kubernetes.io/docs/concepts/scheduling-eviction/taint-and-toleration/](https://kubernetes.io/docs/concepts/scheduling-eviction/taint-and-toleration/) *** This completes the manual scheduling exercise: create a Pod, diagnose Pending status due to a missing scheduler, and manually schedule it using `nodeName`. 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