Node troubleshooting in Kubernetes - Cheat Sheet & Quick Revision

Recall & Review

beginner

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

Use kubectl get nodes to see the status, roles, and age of all nodes in the cluster.

beginner

How can you describe a specific node to get detailed information?

Use kubectl describe node <node-name> to get detailed info like conditions, capacity, and events related to that node.

intermediate

What does it mean if a node is in 'NotReady' state?

A 'NotReady' node means Kubernetes cannot schedule pods on it because it failed health checks or lost connection.

intermediate

Which logs are useful to check when troubleshooting node issues?

Check the kubelet logs on the node using <code>journalctl -u kubelet</code> or system logs to find errors causing node problems.

intermediate

How can you safely remove a problematic node from the cluster?

First, drain the node with kubectl drain <node-name> --ignore-daemonsets to move pods away, then delete it with kubectl delete node <node-name>.

Which command lists all nodes and their status in Kubernetes?

A kubectl get nodes

B kubectl get pods

C kubectl describe pods

D kubectl get services

kubectl get nodes shows all nodes and their status.

What does the 'NotReady' status on a node indicate?

A Node is healthy and ready

B Node is unreachable or failing health checks

C Node is running pods normally

D Node is being deleted

'NotReady' means the node is unreachable or failing health checks.

How do you get detailed information about a node's conditions and events?

A kubectl describe node <node-name>

B kubectl get nodes

C kubectl logs node

D kubectl get pods

kubectl describe node <node-name> shows detailed info about the node.

Which logs are most helpful to check when a node has issues?

A Pod logs

B API server logs

C Service logs

D kubelet logs on the node

Kubelet logs on the node help diagnose node problems.

What is the correct order to safely remove a node from a cluster?

A Delete node, then drain it

B Restart node, then delete it

C Drain node, then delete it

D Delete pods, then delete node

Drain the node first to move pods, then delete the node.

Explain the steps you would take to troubleshoot a Kubernetes node that shows 'NotReady' status.

Start by checking status and logs, then move to deeper investigation.

Describe how to safely remove a node from a Kubernetes cluster and why each step is important.

Think about pod safety and cluster health.

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