kubectl logs for debugging in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to show logs of a pod named 'webapp'.

Kubernetes

kubectl logs [1]

Drag options to blanks, or click blank then click option'

Aget pods

Bwebapp

Cdelete pod

Ddescribe pod

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'get pods' instead of the pod name.

Using 'describe pod' which shows details, not logs.

The command kubectl logs webapp shows the logs of the pod named 'webapp'.

2fill in blank

medium

Complete the command to follow logs of the pod 'backend' in real-time.

Kubernetes

kubectl logs -f [1]

Drag options to blanks, or click blank then click option'

Adatabase

Bfrontend

Cbackend

Dcache

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong pod name.

Forgetting the -f flag to follow logs.

The -f flag streams logs live. Use kubectl logs -f backend to follow logs of the 'backend' pod.

3fill in blank

hard

Fix the error in the command to get logs from the container 'api' inside pod 'service'.

Kubernetes

kubectl logs [1] -c api

Drag options to blanks, or click blank then click option'

Apod

Bapi

Ccontainer

Dservice

Attempts:

3 left

💡 Hint

Common Mistakes

Using container name instead of pod name.

Placing container name before pod name.

The pod name must be specified before the -c container flag. Use kubectl logs service -c api.

4fill in blank

hard

Fill both blanks to get logs from the previous instance of pod 'worker' container 'job'.

Kubernetes

kubectl logs [1] -c [2] --previous

Drag options to blanks, or click blank then click option'

Aworker

Bjob

Cservice

Dapi

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing pod and container names.

Forgetting the --previous flag.

Use kubectl logs worker -c job --previous to see logs from the previous container instance.

5fill in blank

hard

Fill all three blanks to get logs from all containers in pod 'app' and follow them live.

Kubernetes

kubectl logs [1] [2] [3]

Drag options to blanks, or click blank then click option'

A-f

B-l

C--all-containers=true

Dapp

Attempts:

3 left

💡 Hint

Common Mistakes

Missing the --all-containers=true flag.

Wrong order of flags.

The command kubectl logs app -f --all-containers=true streams logs live from all containers in the 'app' pod.

Practice

1. What does the kubectl logs command do in Kubernetes?

easy

A. Deletes a pod from the cluster

B. Lists all pods running in the cluster

C. Creates a new pod with specified configuration

D. Shows the output logs of a container inside a pod

Solution

1. Step 1: Understand the purpose of kubectl logs

   This command is used to view the logs generated by containers running inside pods in Kubernetes.

2. Step 2: Differentiate from other commands

   Deleting pods uses kubectl delete, creating pods uses kubectl create, and listing pods uses kubectl get pods. None of these show logs.

3. Final Answer:

   Shows the output logs of a container inside a pod -> Option D

4. Quick Check:

   Logs = Output from container [OK]

Hint: Logs show container output, not pod creation or deletion [OK]

Common Mistakes:

• Confusing logs with pod creation or deletion
• Thinking logs list pods instead of showing output
• Assuming logs show cluster-wide events

2. Which of the following is the correct syntax to follow logs live from a pod named webapp-123?

easy

A. kubectl logs webapp-123 --follow

B. kubectl logs --tail webapp-123

C. kubectl logs webapp-123 -t

D. kubectl logs -t webapp-123

Solution

1. Step 1: Recall correct flag placement

   The --follow flag comes after the pod name in the kubectl logs command syntax.

2. Step 2: Check distractor flags

   Distractors use --tail (shows last lines, no streaming) or -t (timestamps, no follow). Only --follow streams live.

3. Final Answer:

   kubectl logs webapp-123 --follow -> Option A

4. Quick Check:

   Pod name first, then flags [OK]

Hint: Put pod name before flags like --follow [OK]

Common Mistakes:

• Placing flags before pod name
• Using --tail or -t instead of --follow
• Mixing order of arguments

3. Given the command kubectl logs mypod --tail=5, what will be the output?

medium

A. Shows all logs except the last 5 lines from the pod named mypod

B. Shows the first 5 lines of logs from the pod named mypod

C. Shows the last 5 lines of logs from the pod named mypod

D. Shows logs only if the pod has more than 5 containers

Solution

1. Step 1: Understand the --tail option

   The --tail=5 option limits the output to the last 5 lines of the logs.

2. Step 2: Confirm it applies to the specified pod

   The command targets the pod named mypod, so logs shown are from that pod only.

3. Final Answer:

   Shows the last 5 lines of logs from the pod named mypod -> Option C

4. Quick Check:

   --tail = last lines [OK]

Hint: --tail shows last lines, not first [OK]

Common Mistakes:

• Thinking --tail shows first lines
• Confusing pod logs with container logs
• Assuming it filters by container count

4. You run kubectl logs mypod -c mycontainer but get an error saying container not found. What is the likely cause?

medium

A. The pod mypod is not running

B. The container name mycontainer does not exist in pod mypod

C. You forgot to add the --follow flag

D. The pod mypod has multiple containers but you did not specify one

Solution

1. Step 1: Analyze the error message

   The error says container not found, which means the container name given is incorrect or missing in the pod.

2. Step 2: Check command correctness

   You specified -c mycontainer, so if the container name is wrong, the error appears. Pod running state or missing --follow flag does not cause this error.

3. Final Answer:

   The container name mycontainer does not exist in pod mypod -> Option B

4. Quick Check:

   Container name must match exactly [OK]

Hint: Check container name spelling matches pod's containers [OK]

Common Mistakes:

• Assuming pod state causes container not found error
• Forgetting to specify container when multiple exist
• Using wrong flag for container name

5. You want to debug a pod with two containers named frontend and backend. Which command correctly streams live logs from the backend container only?

hard

A. kubectl logs podname -c backend --follow

B. kubectl logs podname --tail -c backend

C. kubectl logs -c backend podname --tail

D. kubectl logs --tail podname -c backend

Solution

1. Step 1: Recall correct argument order

   The pod name must come immediately after kubectl logs, followed by flags like -c and --follow.

2. Step 2: Confirm container and follow flag usage

   Using -c backend specifies the backend container, and --follow streams logs live.

3. Final Answer:

   kubectl logs podname -c backend --follow -> Option A

4. Quick Check:

   Pod name first, then container and flags [OK]

Hint: Pod name first, then container (-c) and --follow [OK]

Common Mistakes:

• Placing flags before pod name
• Mixing order of container and follow flags
• Using unsupported shorthand flags