Metrics Server installation in Kubernetes - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the Metrics Server in Kubernetes?

The Metrics Server collects resource usage data like CPU and memory from nodes and pods. It helps Kubernetes make decisions for scaling and monitoring.

beginner

Which command installs the Metrics Server using kubectl?

kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml

intermediate

Why might you need to edit the Metrics Server deployment after installation?

You may need to add flags like --kubelet-insecure-tls if your cluster uses self-signed certificates, to allow Metrics Server to communicate with kubelets.

beginner

How can you verify that the Metrics Server is running correctly?

Run kubectl get deployment metrics-server -n kube-system to check the deployment status and kubectl top nodes to see if metrics are available.

intermediate

What role does the Metrics Server play in Horizontal Pod Autoscaling (HPA)?

Metrics Server provides the resource usage data that HPA uses to decide when to scale pods up or down based on CPU or memory usage.

Which command installs the Metrics Server in Kubernetes?

A kubectl create deployment metrics-server

B kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml

C kubectl install metrics-server

D kubectl get metrics-server

The correct command applies the official Metrics Server manifest from the GitHub repository.

What does the Metrics Server collect from Kubernetes nodes and pods?

A Network traffic data

B Pod logs

C Resource usage data like CPU and memory

D Persistent volume usage

Metrics Server collects CPU and memory usage metrics, not logs or network data.

If Metrics Server cannot communicate with kubelets due to TLS errors, what flag might you add?

A --kubelet-insecure-tls

B --enable-logging

C --allow-unauthenticated

D --disable-metrics

The --kubelet-insecure-tls flag allows Metrics Server to skip TLS verification for kubelet communication.

How do you check if Metrics Server is successfully deployed?

A kubectl logs metrics-server

B kubectl get pods -n default

C kubectl describe node

D kubectl get deployment metrics-server -n kube-system

Checking the deployment status in the kube-system namespace confirms if Metrics Server is running.

What Kubernetes feature depends on Metrics Server for scaling decisions?

A Horizontal Pod Autoscaler (HPA)

B kubectl rollout

C kubectl exec

D Persistent Volume Claims

HPA uses Metrics Server data to scale pods based on resource usage.

Explain the steps to install and verify the Metrics Server in a Kubernetes cluster.

Think about installation, deployment check, and metrics verification commands.

Describe why Metrics Server might need configuration changes after installation and what those changes could be.

Consider common issues with self-signed certificates in clusters.

Practice

1. What is the primary purpose of the Kubernetes Metrics Server?

easy

A. To schedule pods on specific nodes

B. To collect live CPU and memory usage data from cluster nodes and pods

C. To store persistent data for applications

D. To manage network policies between pods

Solution

1. Step 1: Understand Metrics Server role

   The Metrics Server collects resource usage data like CPU and memory from nodes and pods in the cluster.

2. Step 2: Differentiate from other components

   It does not manage network policies, store data, or schedule pods, which are handled by other Kubernetes components.

3. Final Answer:

   To collect live CPU and memory usage data from cluster nodes and pods -> Option B

4. Quick Check:

   Metrics Server = resource usage data collection [OK]

Hint: Metrics Server = live resource data collector [OK]

Common Mistakes:

• Confusing Metrics Server with network or storage components
• Thinking it schedules pods
• Assuming it stores persistent data

2. Which command correctly installs the Metrics Server in a Kubernetes cluster?

easy

A. kubectl run metrics-server --image=metrics-server:latest

B. kubectl create deployment metrics-server

C. kubectl install metrics-server

D. kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml

Solution

1. Step 1: Identify official installation method

   The Metrics Server is installed by applying the official components.yaml manifest from the Kubernetes SIGs GitHub repository using kubectl apply.

2. Step 2: Check command correctness

   Only kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml uses kubectl apply with the correct URL. Other options use incorrect commands or methods.

3. Final Answer:

   kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml -> Option D

4. Quick Check:

   Install Metrics Server = kubectl apply official manifest [OK]

Hint: Use kubectl apply with official components.yaml URL [OK]

Common Mistakes:

• Using kubectl create or run instead of apply
• Missing the full URL to the manifest
• Trying to install with a non-existent command

3. After installing Metrics Server, what is the expected output of kubectl top nodes?

medium

A. A list showing CPU and memory usage for each node

B. An error saying Metrics Server is not found

C. A list of pods running on each node

D. No output, command does nothing

Solution

1. Step 1: Understand kubectl top nodes command

   This command shows current CPU and memory usage metrics for each node in the cluster, provided Metrics Server is installed and working.

2. Step 2: Identify expected output

   With Metrics Server installed, it returns a table listing nodes with their CPU and memory usage. Errors or empty output indicate installation or connectivity issues.

3. Final Answer:

   A list showing CPU and memory usage for each node -> Option A

4. Quick Check:

   kubectl top nodes = node resource usage list [OK]

Hint: kubectl top nodes shows node CPU/memory usage [OK]

Common Mistakes:

• Expecting pod lists instead of metrics
• Assuming command fails after installation
• Confusing with other kubectl commands

4. You installed Metrics Server but kubectl top pods returns an error. What is the most likely cause?

medium

A. Metrics Server is not running or has permission issues

B. kubectl top pods command is deprecated

C. You need to restart the Kubernetes cluster

D. Pods do not have resource limits set

Solution

1. Step 1: Analyze error cause

   If kubectl top pods fails, it usually means Metrics Server is not running properly or lacks permissions to gather metrics.

2. Step 2: Rule out other options

   The command is not deprecated, cluster restart is rarely needed, and missing resource limits does not cause this error.

3. Final Answer:

   Metrics Server is not running or has permission issues -> Option A

4. Quick Check:

   kubectl top pods error = Metrics Server problem [OK]

Hint: Check Metrics Server pod status and permissions first [OK]

Common Mistakes:

• Assuming kubectl top pods is deprecated
• Restarting cluster unnecessarily
• Thinking resource limits cause command failure

5. You want to install Metrics Server but your cluster nodes use self-signed certificates causing TLS errors. What is the best way to fix this during installation?

hard

A. Disable TLS on all cluster nodes

B. Install Metrics Server without any changes; it will auto-fix TLS

C. Edit the Metrics Server deployment to add --kubelet-insecure-tls argument

D. Use a different monitoring tool that does not require TLS

Solution

1. Step 1: Identify TLS issue cause

   Self-signed certificates cause TLS verification errors when Metrics Server connects to kubelets.

2. Step 2: Apply correct fix

   Adding the --kubelet-insecure-tls flag to Metrics Server deployment disables strict TLS verification, allowing it to work with self-signed certs.

3. Step 3: Rule out unsafe or incorrect options

   Disabling TLS cluster-wide is unsafe, Metrics Server does not auto-fix TLS, and switching tools is unnecessary.

4. Final Answer:

   Edit the Metrics Server deployment to add --kubelet-insecure-tls argument -> Option C

5. Quick Check:

   Self-signed certs fix = add --kubelet-insecure-tls [OK]

Hint: Add --kubelet-insecure-tls flag for self-signed certs [OK]

Common Mistakes:

• Disabling TLS on nodes (unsafe)
• Expecting Metrics Server to auto-fix TLS
• Ignoring TLS errors and proceeding