Node troubleshooting in Kubernetes - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

Check node status with kubectl

You run the command kubectl get nodes on your cluster. What output indicates that a node is NotReady?

Kubernetes

kubectl get nodes

A

NAME       STATUS     ROLES    AGE   VERSION
node1      Ready      worker   10d   v1.26.0
node2      NotReady   worker   10d   v1.26.0

B

NAME       STATUS     ROLES    AGE   VERSION
node1      Ready      master   10d   v1.26.0
node2      Ready      worker   10d   v1.26.0

C

NAME       STATUS     ROLES    AGE   VERSION
node1      Unknown    worker   10d   v1.26.0
node2      Ready      worker   10d   v1.26.0

D

NAME       STATUS     ROLES    AGE   VERSION
node1      Ready      worker   10d   v1.26.0
node2      SchedulingDisabled   worker   10d   v1.26.0

💡 Hint

Look for the STATUS column showing node health.

The NotReady status means the node is not healthy and cannot run pods. Other statuses like Ready or SchedulingDisabled mean different states.

❓ Troubleshoot

intermediate

Diagnose node unreachable error

You notice pods stuck in Pending state and suspect a node is unreachable. Which command helps you check node connectivity issues?

A kubectl logs <pod-name>

B kubectl get pods --all-namespaces

C kubectl exec <pod-name> -- ping 8.8.8.8

D kubectl describe node <node-name>

💡 Hint

You want detailed info about the node itself.

The kubectl describe node command shows node conditions, including network or disk pressure, which helps diagnose connectivity problems.

❓ Configuration

advanced

Identify correct kubelet config for node readiness

Which kubelet configuration option ensures the node reports Ready status only when the node is healthy?

A --fail-swap-on=false

B --read-only-port=10255

C --eviction-hard=memory.available<500Mi,nodefs.available<10%

D --node-status-update-frequency=10s

💡 Hint

Look for settings that control node health eviction.

The --eviction-hard flag sets thresholds for resource pressure. If these are exceeded, the node becomes NotReady to protect stability.

🔀 Workflow

advanced

Sequence to safely drain a node

What is the correct order of commands to safely drain a node before maintenance?

A 2,1,3,4

B 1,2,3,4

C 1,3,2,4

D 4,1,2,3

💡 Hint

First prevent new pods, then move existing pods, then allow scheduling again.

You first mark the node unschedulable with cordon, then safely evict pods with drain. After maintenance, use uncordon to allow pods again.

✅ Best Practice

expert

Identify best practice for node failure alerting

Which approach is best to get immediate alerts when a Kubernetes node becomes NotReady?

A Set up Prometheus to monitor node status and alert on <code>NotReady</code> condition

B Restart kubelet service on all nodes daily

C Use <code>kubectl logs</code> on pods to check node health

D Manually run <code>kubectl get nodes</code> every hour

💡 Hint

Automated monitoring and alerting is key for fast response.

Prometheus can scrape node metrics and alert immediately when a node status changes to NotReady, enabling quick action.

Practice

1. What command shows the current status of all nodes in a Kubernetes cluster?

easy

A. kubectl get nodes

B. kubectl describe pods

C. kubectl get pods

D. kubectl top pods

Solution

1. Step 1: Understand the command purpose

   kubectl get nodes lists all nodes and their status in the cluster.

2. Step 2: Compare with other commands

   Other commands focus on pods, not nodes, so they don't show node status.

3. Final Answer:

   kubectl get nodes -> Option A

4. Quick Check:

   Node status = kubectl get nodes [OK]

Hint: Use 'kubectl get nodes' to see node status quickly [OK]

Common Mistakes:

• Confusing pods with nodes
• Using describe instead of get for quick status
• Trying 'kubectl top pods' for node info

2. Which command syntax correctly shows detailed information about a specific node named node-1?

easy

A. kubectl describe node node-1

B. kubectl get node node-1

C. kubectl get nodes node-1

D. kubectl describe nodes node-1

Solution

1. Step 1: Identify correct command for detailed info

   kubectl describe node node-1 shows detailed info about the node named node-1.

2. Step 2: Check syntax correctness

   Singular 'node' is correct here; plural 'nodes' is invalid for describing a single node. 'get' shows summary, not details.

3. Final Answer:

   kubectl describe node node-1 -> Option A

4. Quick Check:

   Detailed node info = kubectl describe node [OK]

Hint: Use singular 'node' with describe for a specific node [OK]

Common Mistakes:

• Using plural 'nodes' with describe for a single node
• Using 'get' instead of 'describe' for details
• Omitting the node name

3. What is the expected output of the command kubectl top node?

medium

A. A list of pods with their resource requests

B. A list of nodes with CPU and memory usage metrics

C. Detailed node configuration and labels

D. A list of nodes with their IP addresses only

Solution

1. Step 1: Understand the purpose of 'kubectl top node'

   This command shows resource usage like CPU and memory for each node.

2. Step 2: Differentiate from other outputs

   It does not show pod info, detailed config, or just IP addresses.

3. Final Answer:

   A list of nodes with CPU and memory usage metrics -> Option B

4. Quick Check:

   Resource usage per node = kubectl top node [OK]

Hint: Top command shows resource usage, not config or IPs [OK]

Common Mistakes:

• Confusing node metrics with pod metrics
• Expecting detailed config from 'top' command
• Thinking it shows only IP addresses

4. You run kubectl describe node node-2 and see the node is in NotReady state. What is the best first step to troubleshoot?

medium

A. Run kubectl get pods to check pod status

B. Delete the node from the cluster immediately

C. Restart all pods on the node manually

D. Check the node's events section for errors or warnings

Solution

1. Step 1: Review node events for clues

   The events section in the describe output shows recent errors or warnings causing NotReady state.

2. Step 2: Avoid premature actions

   Deleting node or restarting pods without info can cause disruption; checking events is safer first step.

3. Final Answer:

   Check the node's events section for errors or warnings -> Option D

4. Quick Check:

   Check events first when node NotReady [OK]

Hint: Look at node events to find issues first [OK]

Common Mistakes:

• Deleting node without diagnosis
• Restarting pods blindly
• Checking pods instead of node events first

5. A node shows high CPU usage and pods are evicted frequently. Which combined steps help troubleshoot and fix this?

hard

A. Scale down all deployments to zero immediately

B. Delete the node and recreate it to reset CPU usage

C. Use kubectl top node to confirm CPU load, then check pod resource requests and limits

D. Run kubectl describe pod on all pods to find errors

Solution

1. Step 1: Confirm node CPU usage

   Run kubectl top node to verify high CPU load on the node.

2. Step 2: Check pod resource settings

   Review pods' resource requests and limits to see if they are causing CPU overload and evictions.

3. Step 3: Adjust resources or scale pods

   Based on findings, adjust pod resource limits or scale workloads to reduce CPU pressure.

4. Final Answer:

   Use kubectl top node to confirm CPU load, then check pod resource requests and limits -> Option C

5. Quick Check:

   Check CPU usage and pod limits to fix evictions [OK]

Hint: Check node CPU then pod limits to fix evictions [OK]

Common Mistakes:

• Deleting node without analysis
• Scaling down all deployments blindly
• Checking pods errors without resource context