Viewing Pod details and logs in Kubernetes - Commands & Configuration

Introduction

Sometimes your app inside Kubernetes pods may not work as expected. You need to look inside the pod to see what is happening and check its logs to find errors or messages.

When you want to check if a pod is running correctly after deployment

When your application inside the pod crashes or behaves unexpectedly

When you want to see real-time output or error messages from your app

When you need to understand why a pod is restarting frequently

When debugging network or configuration issues inside a pod

Commands

This command lists all pods in the current namespace so you can find the pod name you want to inspect.

Terminal

kubectl get pods

Expected Output

NAME           READY   STATUS    RESTARTS   AGE

my-app-pod     1/1     Running   0          3m

This command shows detailed information about the pod, including its status, events, and resource usage. It helps you understand the pod's current state and any recent issues.

Terminal

kubectl describe pod my-app-pod

Expected Output

Name:         my-app-pod

Namespace:    default

Node:         node-1

Start Time:   Thu, 01 Jun 2024 10:00:00 +0000

Labels:       app=my-app

Status:       Running

IP:           10.244.1.5

Containers:

  my-app-container:

    Container ID:   docker://abcdef123456

    Image:          my-app-image:1.0

    State:          Running

    Ready:          True

    Restart Count:  0

Events:

  Type    Reason     Age   From               Message

  ----    ------     ----  ----               -------

  Normal  Scheduled  5m    default-scheduler  Successfully assigned default/my-app-pod to node-1

This command fetches the logs from the main container inside the pod. Logs show what the app is printing, including errors and info messages.

Terminal

kubectl logs my-app-pod

Expected Output

2024-06-01T10:01:00Z Starting application

2024-06-01T10:01:05Z Application ready to accept requests

This command streams the logs live, so you can watch new log messages as they appear. Useful for real-time debugging.

Terminal

kubectl logs -f my-app-pod

Expected Output

2024-06-01T10:01:00Z Starting application

2024-06-01T10:01:05Z Application ready to accept requests

2024-06-01T10:02:00Z Received request from user

→

-f - Follow logs live as new lines appear

Key Concept

If you remember nothing else from this pattern, remember: use 'kubectl describe pod' for detailed pod info and 'kubectl logs' to see what your app is saying.

Common Mistakes

Trying to get logs from a pod name that does not exist

kubectl will return an error because it cannot find the pod to get logs from

Run 'kubectl get pods' first to find the correct pod name before fetching logs

Not specifying the container name when a pod has multiple containers

kubectl logs will fail or show logs from the wrong container

Use 'kubectl logs my-app-pod -c container-name' to specify which container's logs to view

Not using the '-f' flag when wanting to see live logs

You only get static logs up to the command run time, missing new log entries

Add '-f' to stream logs live for real-time monitoring

Summary

Use 'kubectl get pods' to list pods and find the pod name.

Use 'kubectl describe pod <pod-name>' to see detailed pod information and events.

Use 'kubectl logs <pod-name>' to view the application logs inside the pod.

Use 'kubectl logs -f <pod-name>' to stream logs live for real-time debugging.

Practice

1. What command shows detailed information and events about a specific Kubernetes pod?

easy

A. kubectl exec <pod-name> -- ls

B. kubectl get pods

C. kubectl logs <pod-name>

D. kubectl describe pod <pod-name>

Solution

1. Step 1: Understand the purpose of each command

   kubectl describe pod <pod-name> shows detailed info and events; kubectl get pods lists pods; kubectl logs shows logs; kubectl exec runs commands inside pod.

2. Step 2: Identify the command for detailed pod info

   The command that shows detailed pod information and events is kubectl describe pod <pod-name>.

3. Final Answer:

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

4. Quick Check:

   Detailed pod info = kubectl describe pod [OK]

Hint: Use 'kubectl describe pod' for detailed pod info and events [OK]

Common Mistakes:

• Using 'kubectl get pods' to see detailed info
• Confusing 'kubectl logs' with pod description
• Trying 'kubectl exec' to get pod events

2. Which of the following is the correct syntax to view logs of a pod named myapp-pod?

easy

A. kubectl get logs myapp-pod

B. kubectl logs myapp-pod

C. kubectl describe logs myapp-pod

D. kubectl show logs myapp-pod

Solution

1. Step 1: Recall the correct command for viewing pod logs

   The command to view logs is kubectl logs <pod-name>.

2. Step 2: Match the correct syntax

   Only kubectl logs myapp-pod matches the correct syntax; others are invalid commands.

3. Final Answer:

   kubectl logs myapp-pod -> Option B

4. Quick Check:

   View pod logs = kubectl logs [OK]

Hint: Use 'kubectl logs pod-name' to see pod logs quickly [OK]

Common Mistakes:

• Adding extra words like 'get' or 'describe' with logs
• Using 'kubectl show' which is not a valid command
• Confusing logs command with describe

3. What will be the output of the command kubectl logs mypod --follow?

medium

A. It shows the logs of 'mypod' and continues to stream new log entries live.

B. It shows only the last 10 lines of logs from 'mypod'.

C. It describes the pod 'mypod' with detailed info and events.

D. It executes a shell inside the 'mypod' container.

Solution

1. Step 1: Understand the '--follow' flag with 'kubectl logs'

   The '--follow' option streams logs live, showing new entries as they appear.

2. Step 2: Match the output description

   The command outputs current logs and keeps streaming new logs live for 'mypod'.

3. Final Answer:

   It shows the logs of 'mypod' and continues to stream new log entries live. -> Option A

4. Quick Check:

   kubectl logs --follow = live log streaming [OK]

Hint: Add '--follow' to stream pod logs live as they appear [OK]

Common Mistakes:

• Thinking '--follow' limits logs to last 10 lines
• Confusing logs with pod description
• Assuming it opens a shell inside the pod

4. You run kubectl logs mypod but get an error saying "a container name must be specified for pod mypod". What is the likely cause?

medium

A. The pod 'mypod' has multiple containers and you did not specify which container's logs to show.

B. The pod 'mypod' does not exist in the cluster.

C. You need to use 'kubectl describe pod mypod' instead of logs.

D. The pod 'mypod' is not running yet.

Solution

1. Step 1: Understand the error message

   The error says a container name must be specified, which happens if the pod has multiple containers.

2. Step 2: Identify the cause

   When a pod has more than one container, you must specify which container's logs you want using -c <container-name>.

3. Final Answer:

   The pod 'mypod' has multiple containers and you did not specify which container's logs to show. -> Option A

4. Quick Check:

   Multiple containers need container name for logs [OK]

Hint: Add '-c container-name' if pod has multiple containers [OK]

Common Mistakes:

• Assuming pod doesn't exist without checking
• Using describe instead of logs for viewing logs
• Ignoring container name requirement for multi-container pods

5. You want to monitor logs of a pod named webserver continuously but only for the container named nginx. Which command should you use?

hard

A. kubectl logs webserver --container nginx

B. kubectl describe pod webserver -c nginx --follow

C. kubectl logs webserver -c nginx --follow

D. kubectl logs webserver --tail=0

Solution

1. Step 1: Identify the need to specify container and follow logs

   To monitor logs continuously, use --follow. For multi-container pods, specify container with -c <container-name>.

2. Step 2: Match the correct command syntax

   kubectl logs webserver -c nginx --follow correctly specifies container and streams logs live.

3. Final Answer:

   kubectl logs webserver -c nginx --follow -> Option C

4. Quick Check:

   Use '-c' for container and '--follow' to stream logs [OK]

Hint: Use '-c container --follow' to stream specific container logs live [OK]

Common Mistakes:

• Using 'describe' instead of 'logs' to view logs
• Using '--container' instead of '-c' which is invalid
• Using '--tail=0' which shows no logs