Metrics Server installation in Kubernetes - Step-by-Step Execution

Process Flow - Metrics Server installation

Download Metrics Server YAML

↓

Apply YAML to cluster

↓

Metrics Server Pods start

↓

Check Pod status

↓

Metrics Server running

↓

kubectl top nodes/pods works

This flow shows downloading the Metrics Server setup file, applying it to the cluster, starting pods, checking their status, and verifying metrics availability.

Execution Sample

Kubernetes

kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml
kubectl get pods -n kube-system
kubectl top nodes

These commands install Metrics Server, check pod status, and display node metrics.

Process Table

Step	Command	Action	Result/Output
1	kubectl apply -f https://github.com/kubernetes-sigs/metrics-server/releases/latest/download/components.yaml	Apply Metrics Server manifests	deployment.apps/metrics-server created serviceaccount/metrics-server created clusterrole.rbac.authorization.k8s.io/metrics-server created ...
2	kubectl get pods -n kube-system	Check Metrics Server pod status	NAME READY STATUS RESTARTS AGE metrics-server-abcdef123-xyz 1/1 Running 0 30s
3	kubectl top nodes	Query node metrics	NAME CPU(cores) MEMORY(bytes) worker-node1 100m 200Mi
4	kubectl top pods	Query pod metrics	NAME CPU(cores) MEMORY(bytes) metrics-server-abcdef123-xyz 5m 20Mi
5	kubectl get pods -n kube-system	If pod not ready	NAME READY STATUS RESTARTS AGE metrics-server-abcdef123-xyz 0/1 CrashLoopBackOff 3 2m
6	Troubleshoot logs	Check pod logs	Error: unable to fetch metrics from Kubelet
7	Fix args in deployment	Add --kubelet-insecure-tls flag	Pod restarts and becomes Ready
8	kubectl top nodes	Verify metrics after fix	NAME CPU(cores) MEMORY(bytes) worker-node1 100m 200Mi

💡 Metrics Server pod is running and metrics commands return data successfully

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 7	Final
Metrics Server Pod Status	Not created	Creating	Running (1/1)	Running (1/1)	Restarting with fix	Running (1/1)
Metrics Availability	No metrics	No metrics	No metrics	No metrics	Metrics shown	Metrics shown

Key Moments - 3 Insights

Why does 'kubectl top nodes' show no metrics right after installation?

Because the Metrics Server pod may not be fully running yet (see step 2 in execution_table), so metrics are not available until pod is Ready.

What does it mean if the Metrics Server pod is in CrashLoopBackOff?

It means the pod is repeatedly failing to start, often due to TLS or permission issues. See step 5 and 6 for troubleshooting logs.

Why add the --kubelet-insecure-tls flag in the deployment?

This flag allows Metrics Server to connect to kubelets without strict TLS verification, fixing common connection errors shown in step 6.

Visual Quiz - 3 Questions

Look at the execution_table, at which step does the Metrics Server pod first show as Running?

A Step 2

B Step 1

C Step 5

D Step 7

💡 Hint

Check the 'Result/Output' column for pod status in step 2.

According to variable_tracker, what is the Metrics Availability state after Step 3?

A Metrics shown

B Pod not created

C No metrics

D Pod crashing

💡 Hint

Look at the 'Metrics Availability' row under 'After Step 3' column.

If the Metrics Server pod is in CrashLoopBackOff, what should you do next according to the execution_table?

A Run 'kubectl top nodes' again

B Check pod logs and fix deployment args

C Delete the pod and reinstall Kubernetes

D Ignore and wait

💡 Hint

See steps 5 and 6 for pod status and logs, and step 7 for the fix.

Concept Snapshot

Metrics Server installation:
1. Download and apply Metrics Server YAML.
2. Check pod status in kube-system namespace.
3. Use 'kubectl top' to view metrics.
4. Troubleshoot pod issues with logs.
5. Add --kubelet-insecure-tls if TLS errors occur.
6. Confirm metrics availability after pod is Ready.

Full Transcript

To install Metrics Server in Kubernetes, first download and apply the official YAML manifest. This creates the Metrics Server deployment and related resources. Next, check the pod status in the kube-system namespace to ensure the pod is running. If the pod is not ready or crashes, check the pod logs for errors such as TLS connection issues. A common fix is to add the --kubelet-insecure-tls flag to the deployment arguments to allow insecure TLS connections to kubelets. Once the pod is running, use 'kubectl top nodes' and 'kubectl top pods' to verify metrics are available. This process ensures Metrics Server is properly installed and functional.

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