Exec probe configuration in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define an exec liveness probe command in a Kubernetes pod spec.

Kubernetes

livenessProbe:
  exec:
    command:
      - [1]

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

Acat

Bcurl

Cls

Decho

Attempts:

3 left

💡 Hint

Common Mistakes

Using commands that require network like curl in exec probe without network setup.

The cat command is commonly used in exec probes to check file contents or presence.

2fill in blank

medium

Complete the code to set the exec probe to check the file '/tmp/healthy'.

Kubernetes

livenessProbe:
  exec:
    command:
      - cat
      - [1]

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

A/etc/healthy

B/home/healthy

C/tmp/healthy

D/var/log/healthy

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing wrong file paths that do not exist in the container.

The exec probe should check the file /tmp/healthy as specified.

3fill in blank

hard

Fix the error in the exec probe command to correctly check the file '/healthz'.

Kubernetes

livenessProbe:
  exec:
    command:
      - [1]
      - [2]

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

Acat /healthz

Bcat

Cls /healthz

D/healthz

Attempts:

3 left

💡 Hint

Common Mistakes

Putting command and argument together as one string causing syntax error.

The command list must separate command and arguments. Use cat as command and /healthz as argument in separate list items.

4fill in blank

hard

Fill both blanks to define an exec readiness probe that runs 'cat /ready'.

Kubernetes

readinessProbe:
  exec:
    command:
      - [1]
      - [2]

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

Acat

B/ready

C/healthz

Dls

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping command and argument positions.

The command is cat and the argument is /ready to check readiness.

5fill in blank

hard

Fill all three blanks to define an exec startup probe that runs 'test -f /startup'.

Kubernetes

startupProbe:
  exec:
    command:
      - [1]
      - [2]
      - [3]

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

Atest

B-f

C/startup

D-e

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong file check option like '-e' instead of '-f'.

The command test -f /startup checks if the file /startup exists.

Practice

1. What is the main purpose of an exec probe in Kubernetes?

easy

A. To schedule pods on specific nodes

B. To expose container ports to the outside world

C. To create persistent storage volumes

D. To run a command inside a container to check if it is healthy

Solution

1. Step 1: Understand exec probe functionality

   An exec probe runs a command inside the container to check its health status.

2. Step 2: Compare with other options

   Options A, B, and D relate to scheduling, networking, and storage, not health checks.

3. Final Answer:

   To run a command inside a container to check if it is healthy -> Option D

4. Quick Check:

   Exec probe = runs command inside container [OK]

Hint: Exec probe runs commands inside container to check health [OK]

Common Mistakes:

• Confusing exec probe with port exposure
• Thinking exec probe schedules pods
• Mixing exec probe with storage management

2. Which of the following is the correct syntax snippet to define an exec liveness probe in a pod spec?

easy

A. livenessProbe:\n exec:\n command: ['cat', '/tmp/healthy']\n initialDelaySeconds: 5\n periodSeconds: 10

B. livenessProbe:\n httpGet:\n path: /healthz\n port: 8080\n initialDelaySeconds: 5

C. livenessProbe:\n exec:\n command: 'cat /tmp/healthy'\n initialDelaySeconds: 5

D. livenessProbe:\n exec:\n command: cat /tmp/healthy\n initialDelaySeconds: 5

Solution

1. Step 1: Check exec command format

   The command must be an array of strings, e.g., ['cat', '/tmp/healthy'].

2. Step 2: Validate YAML structure

   livenessProbe:\n exec:\n command: ['cat', '/tmp/healthy']\n initialDelaySeconds: 5\n periodSeconds: 10 correctly uses the array syntax and includes initialDelaySeconds and periodSeconds.

3. Final Answer:

   Correct exec probe with command array and delays -> Option A

4. Quick Check:

   Exec command = array of strings [OK]

Hint: Exec command must be a list of strings in YAML [OK]

Common Mistakes:

• Using a single string instead of array for command
• Confusing exec probe with httpGet probe
• Omitting required indentation or keys

3. Given this exec probe configuration in a pod spec:

livenessProbe:
  exec:
    command: ['test', '-f', '/tmp/healthy']
  initialDelaySeconds: 3
  periodSeconds: 5

What happens if the file /tmp/healthy does not exist inside the container?

medium

A. The probe ignores the missing file and logs a warning

B. The probe passes and container continues running

C. The probe fails and Kubernetes restarts the container after retries

D. The container is immediately deleted without restart

Solution

1. Step 1: Understand exec probe command

   The command 'test -f /tmp/healthy' returns success if the file exists, failure if not.

2. Step 2: Effect of probe failure

   If the probe fails repeatedly, Kubernetes restarts the container to recover.

3. Final Answer:

   The probe fails and Kubernetes restarts the container after retries -> Option C

4. Quick Check:

   Missing file = probe fails = restart [OK]

Hint: Missing file causes exec probe failure and container restart [OK]

Common Mistakes:

• Assuming probe passes if file missing
• Thinking container deletes without restart
• Believing probe ignores errors silently

4. You configured an exec readiness probe but your pod never becomes ready. Which of these is the most likely cause?

medium

A. The exec command is missing the command array syntax and uses a single string

B. The initialDelaySeconds is set too high

C. The container image is missing

D. The pod has no resource limits defined

Solution

1. Step 1: Check exec command syntax

   Exec probe commands must be an array of strings; a single string causes probe failure.

2. Step 2: Understand probe failure effect

   If the probe fails, the pod is not marked ready, so it never becomes ready.

3. Final Answer:

   Exec command missing array syntax causes probe failure -> Option A

4. Quick Check:

   Exec command array syntax missing = probe fails [OK]

Hint: Exec command must be array; single string causes failure [OK]

Common Mistakes:

• Ignoring command array syntax errors
• Blaming initialDelaySeconds without checking command
• Confusing readiness with resource limits

5. You want to configure an exec liveness probe that waits 10 seconds before starting, runs the command ['/bin/check.sh'], retries every 5 seconds, and fails after 3 unsuccessful attempts. Which is the correct YAML snippet?

hard

A. livenessProbe:\n exec:\n command: '/bin/check.sh'\n initialDelaySeconds: 10\n periodSeconds: 5\n failureThreshold: 3

B. livenessProbe:\n exec:\n command: ['/bin/check.sh']\n initialDelaySeconds: 10\n periodSeconds: 5\n failureThreshold: 3

C. livenessProbe:\n exec:\n command: ['/bin/check.sh']\n initialDelaySeconds: 5\n periodSeconds: 10\n failureThreshold: 3

D. livenessProbe:\n exec:\n command: ['/bin/check.sh']\n initialDelaySeconds: 10\n periodSeconds: 5\n failureThreshold: 1

Solution

1. Step 1: Verify command syntax and initial delay

   Command must be an array; initialDelaySeconds must be 10 as required.

2. Step 2: Check periodSeconds and failureThreshold

   PeriodSeconds should be 5 for retry every 5 seconds; failureThreshold 3 means fail after 3 tries.

3. Final Answer:

   Correct YAML with command array, initialDelaySeconds 10, periodSeconds 5, failureThreshold 3 -> Option B

4. Quick Check:

   Command array + delays + failureThreshold correct = livenessProbe:\n exec:\n command: ['/bin/check.sh']\n initialDelaySeconds: 10\n periodSeconds: 5\n failureThreshold: 3 [OK]

Hint: Use array for command and set delays and failureThreshold as numbers [OK]

Common Mistakes:

• Using string instead of array for command
• Swapping periodSeconds and initialDelaySeconds values
• Setting failureThreshold too low or missing