Pod stuck in Pending state in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to check the status of pods in the default namespace.

Kubernetes

kubectl get pods --namespace=[1]

Drag options to blanks, or click blank then click option'

Akube-system

Ball

Cdefault

Dpending

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'all' instead of a namespace

Using 'pending' which is a pod status, not a namespace

The default namespace is where most pods run unless specified otherwise. Using default shows pods in that namespace.

2fill in blank

medium

Complete the command to describe a pod named 'myapp-pod' to find why it is Pending.

Kubernetes

kubectl describe pod [1]

Drag options to blanks, or click blank then click option'

Apod-myapp

Bpending-pod

Cmy-pod-app

Dmyapp-pod

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect pod names

Swapping words in the pod name

The pod name must be exact to get detailed info. 'myapp-pod' is the correct pod name here.

3fill in blank

hard

Fix the error in this YAML snippet to request CPU resources correctly for a pod.

Kubernetes

resources:
  requests:
    cpu: [1]

Drag options to blanks, or click blank then click option'

A100m

B100

C0.1

D1000m

Attempts:

3 left

💡 Hint

Common Mistakes

Using plain numbers without units

Using decimal numbers without 'm'

CPU requests in Kubernetes are specified in millicores, like '100m' for 0.1 CPU core.

4fill in blank

hard

Fill both blanks to create a node selector that schedules pods only on nodes labeled with environment=production.

Kubernetes

nodeSelector:
  [1]: [2]

Drag options to blanks, or click blank then click option'

Aenvironment

Bproduction

Cstaging

Dzone

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping key and value

Using wrong label keys or values

Node selectors use key-value pairs. Here, key is 'environment' and value is 'production' to select production nodes.

5fill in blank

hard

Fill all three blanks to create a pod affinity rule that prefers nodes in the 'us-east' zone with label 'zone=us-east'.

Kubernetes

affinity:
  podAffinity:
    preferredDuringSchedulingIgnoredDuringExecution:
    - weight: [1]
      podAffinityTerm:
        labelSelector:
          matchExpressions:
          - key: [2]
            operator: In
            values:
            - [3]

Drag options to blanks, or click blank then click option'

A100

Bzone

Cus-east

Denvironment

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong weight values

Using incorrect label keys or values

The weight defines preference strength (100 is max). The key is 'zone' and the value is 'us-east' to prefer those nodes.

Practice

1. What does it usually mean when a Kubernetes Pod is stuck in the Pending state?

easy

A. Kubernetes cannot find a suitable node to run the Pod.

B. The Pod has completed its task and is terminating.

C. The Pod is running but not responding to requests.

D. The Pod has been deleted from the cluster.

Solution

1. Step 1: Understand Pod lifecycle states

   The Pending state means the Pod is created but not yet scheduled to a node.

2. Step 2: Identify reason for Pending

   Pending usually happens when no node meets the Pod's resource or scheduling requirements.

3. Final Answer:

   Kubernetes cannot find a suitable node to run the Pod. -> Option A

4. Quick Check:

   Pending = No suitable node found [OK]

Hint: Pending means no node fits Pod's needs [OK]

Common Mistakes:

• Confusing Pending with Running state
• Thinking Pending means Pod is deleted
• Assuming Pending means Pod is ready

2. Which kubectl command helps you see detailed reasons why a Pod is stuck in Pending state?

easy

A. kubectl get pods

B. kubectl describe pod

C. kubectl logs

D. kubectl delete pod

Solution

1. Step 1: Identify command to get detailed Pod info

   kubectl describe pod shows events and status details for the Pod.

2. Step 2: Confirm command usage

   This command reveals scheduling failures or resource issues causing Pending.

3. Final Answer:

   kubectl describe pod <pod-name> -> Option B

4. Quick Check:

   Describe Pod = Detailed status [OK]

Hint: Use describe to see Pod events and reasons [OK]

Common Mistakes:

• Using get pods only shows summary, not reasons
• Using logs shows container logs, not scheduling info
• Deleting Pod does not show status

3. Given this kubectl describe pod mypod output snippet:

Events:
  Type     Reason            Age   From               Message
  ----     ------            ----  ----               -------
  Warning  FailedScheduling  2m    default-scheduler  0/3 nodes are available: 3 Insufficient cpu.

What is the main reason the Pod is stuck in Pending?

medium

A. There is no node with enough CPU available.

B. The Pod image is not found.

C. The Pod has a syntax error in its YAML.

D. The Pod is already running on another node.

Solution

1. Step 1: Analyze the event message

   The message says "0/3 nodes are available: 3 Insufficient cpu." meaning no node has enough CPU resources.

2. Step 2: Understand impact on scheduling

   Without enough CPU, the scheduler cannot place the Pod, so it stays Pending.

3. Final Answer:

   There is no node with enough CPU available. -> Option A

4. Quick Check:

   Insufficient CPU = Pod Pending [OK]

Hint: Look for 'Insufficient cpu' in describe events [OK]

Common Mistakes:

• Confusing image errors with scheduling errors
• Assuming YAML syntax causes Pending
• Thinking Pod runs on multiple nodes

4. You see a Pod stuck in Pending state. You check kubectl describe pod and find the message: 0/2 nodes are available: 2 node(s) didn't match Pod's node selector.
What should you do to fix this?

medium

A. Delete the Pod and recreate it without changes.

B. Increase the Pod's CPU requests to match node capacity.

C. Remove or correct the Pod's nodeSelector labels to match available nodes.

D. Restart the Kubernetes cluster.

Solution

1. Step 1: Understand nodeSelector impact

   The Pod's nodeSelector restricts scheduling to nodes with matching labels.

2. Step 2: Fix nodeSelector to match nodes

   Adjust or remove nodeSelector so nodes in cluster match Pod requirements.

3. Final Answer:

   Remove or correct the Pod's nodeSelector labels to match available nodes. -> Option C

4. Quick Check:

   nodeSelector mismatch = fix labels [OK]

Hint: Check and fix nodeSelector labels to match nodes [OK]

Common Mistakes:

• Increasing CPU requests worsens scheduling
• Deleting Pod without fixing selector won't help
• Restarting cluster is unnecessary

5. A Pod requests 4 CPUs but all nodes in your cluster have only 2 CPUs each. The Pod stays Pending. Which is the best way to fix this?

hard

A. Change the Pod's image to a smaller size.

B. Reduce the Pod's CPU request to 2 or less.

C. Remove resource requests from the Pod spec.

D. Add a node with at least 4 CPUs to the cluster.

Solution

1. Step 1: Understand resource requests vs node capacity

   The Pod requests 4 CPUs but nodes have only 2 CPUs, so no node can run it.

2. Step 2: Choose solution to meet resource needs

   Adding a node with enough CPUs allows the Pod to be scheduled properly.

3. Final Answer:

   Add a node with at least 4 CPUs to the cluster. -> Option D

4. Quick Check:

   Pod CPU request > node CPU = add bigger node [OK]

Hint: Match Pod CPU request with node CPU capacity [OK]

Common Mistakes:

• Reducing CPU request may not be possible or desired
• Removing requests can cause unstable scheduling
• Changing image size does not affect CPU requests