Node selectors for simple scheduling in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the YAML to add a node selector that schedules the pod on nodes labeled with environment=production.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: mypod
spec:
  containers:
  - name: mycontainer
    image: nginx
  nodeSelector:
    environment: [1]

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

Astaging

Bproduction

Cdevelopment

Dtest

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong label value like 'staging' instead of 'production'.

Forgetting to indent the nodeSelector properly in YAML.

The nodeSelector key specifies the label key and value to select nodes. Here, environment: production ensures the pod runs on nodes labeled with environment=production.

2fill in blank

medium

Complete the YAML to schedule the pod on nodes labeled with disktype=ssd.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: fastpod
spec:
  containers:
  - name: fastcontainer
    image: busybox
  nodeSelector:
    disktype: [1]

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

Assd

Bnvme

Csata

Dhdd

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'hdd' which means hard disk drive instead of 'ssd'.

Misspelling the label value.

The nodeSelector uses the label disktype: ssd to schedule the pod on nodes with SSD disks.

3fill in blank

hard

Fix the error in the nodeSelector to correctly schedule the pod on nodes labeled with region=us-west.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: regionalpod
spec:
  containers:
  - name: regionalcontainer
    image: alpine
  nodeSelector:
    region: [1]

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

Aasia-south

Bus_east

Ceu-central

Dus-west

Attempts:

3 left

💡 Hint

Common Mistakes

Using underscores instead of hyphens in region names.

Choosing a region label that does not exist on nodes.

The nodeSelector must match the exact label value 'us-west' to schedule the pod on nodes in that region.

4fill in blank

hard

Fill both blanks to schedule the pod on nodes labeled with tier=backend and environment=production.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: backendpod
spec:
  containers:
  - name: backendcontainer
    image: redis
  nodeSelector:
    tier: [1]
    environment: [2]

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

Abackend

Bfrontend

Cproduction

Ddevelopment

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up tier and environment values.

Using 'frontend' or 'development' instead of the correct labels.

The nodeSelector keys 'tier' and 'environment' must match 'backend' and 'production' respectively to schedule the pod on the correct nodes.

5fill in blank

hard

Fill all three blanks to schedule the pod on nodes labeled with role=database, zone=us-central1-a, and environment=staging.

Kubernetes

apiVersion: v1
kind: Pod
metadata:
  name: dbpod
spec:
  containers:
  - name: dbcontainer
    image: postgres
  nodeSelector:
    role: [1]
    zone: [2]
    environment: [3]

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

Awebserver

Bus-central1-a

Cstaging

Ddatabase

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong role like 'webserver' instead of 'database'.

Mixing zone or environment values incorrectly.

The nodeSelector keys 'role', 'zone', and 'environment' must match 'database', 'us-central1-a', and 'staging' respectively to schedule the pod correctly.

Practice

1. What is the main purpose of using nodeSelector in a Kubernetes Pod specification?

easy

A. To limit the number of pods running in the cluster

B. To schedule pods only on nodes with specific labels

C. To automatically update pods when nodes change

D. To create a backup of pod data on nodes

Solution

1. Step 1: Understand nodeSelector role

   The nodeSelector field in a Pod spec is used to specify labels that a node must have for the pod to be scheduled there.

2. Step 2: Compare options with nodeSelector purpose

   Only To schedule pods only on nodes with specific labels correctly describes this scheduling control. Other options describe unrelated features.

3. Final Answer:

   To schedule pods only on nodes with specific labels -> Option B

4. Quick Check:

   nodeSelector = schedule pods on labeled nodes [OK]

Hint: nodeSelector matches pod to node labels for placement [OK]

Common Mistakes:

• Thinking nodeSelector limits pod count
• Confusing nodeSelector with pod updates
• Assuming nodeSelector backs up pod data

2. Which of the following is the correct syntax to specify a nodeSelector in a Pod YAML manifest?

easy

A. nodeSelector: disktype=ssd

B. nodeSelector:
- disktype: ssd

C. nodeSelector:
disktype: ssd

D. nodeSelector: [disktype=ssd]

Solution

1. Step 1: Recall nodeSelector YAML format

   nodeSelector is a map of key-value pairs under the nodeSelector field, indented properly.

2. Step 2: Check each option's syntax

   nodeSelector: disktype: ssd uses correct YAML mapping with key and value properly indented. Options B, C, and D use invalid YAML or wrong formats.

3. Final Answer:

   nodeSelector: disktype: ssd -> Option C

4. Quick Check:

   nodeSelector uses key: value map in YAML [OK]

Hint: Use key: value under nodeSelector with proper indentation [OK]

Common Mistakes:

• Using list syntax instead of map
• Writing nodeSelector as a string
• Incorrect indentation causing YAML errors

3. Given the following node labels:

node1: disktype=ssd
node2: disktype=hdd

And this Pod spec snippet:

spec:
  nodeSelector:
    disktype: ssd

On which node will the Pod be scheduled?

medium

A. node1

B. node2

C. Either node1 or node2

D. No node, pod will remain pending

Solution

1. Step 1: Match pod nodeSelector with node labels

   The pod requires a node with label disktype=ssd. node1 has this label, node2 does not.

2. Step 2: Determine pod scheduling

   Since only node1 matches the label, the pod will be scheduled on node1.

3. Final Answer:

   node1 -> Option A

4. Quick Check:

   Pod nodeSelector matches node1 label [OK]

Hint: Pod schedules only on nodes matching all nodeSelector labels [OK]

Common Mistakes:

• Assuming pod can schedule on any node
• Ignoring label key-value exact match
• Thinking pod schedules on multiple nodes simultaneously

4. You wrote this Pod spec:

spec:
  nodeSelector:
    disk-type: ssd

But your nodes have label disktype=ssd (no dash). What will happen when you try to schedule the Pod?

medium

A. Pod will remain pending, no matching nodes found

B. Pod will schedule on nodes with label disktype=ssd

C. Pod will schedule on nodes with label disk-type=ssd

D. Pod will schedule on any available node

Solution

1. Step 1: Compare nodeSelector key with node labels

   The pod requests nodes with label disk-type=ssd, but nodes have disktype=ssd. The keys differ by a dash.

2. Step 2: Understand label matching behavior

   Labels must match exactly. Since no node has disk-type=ssd, pod cannot be scheduled.

3. Final Answer:

   Pod will remain pending, no matching nodes found -> Option A

4. Quick Check:

   Label keys must match exactly for nodeSelector [OK]

Hint: Label keys must match exactly, including dashes [OK]

Common Mistakes:

• Assuming partial key match works
• Thinking pod schedules on any node if no match
• Confusing label key spelling

5. You want to ensure a Pod runs only on nodes labeled region=us-west and disktype=ssd. Which is the correct nodeSelector configuration?

hard

A. nodeSelector:
region: us-west, disktype: ssd

B. nodeSelector:
region=us-west
disktype=ssd

C. nodeSelector:
- region=us-west
- disktype=ssd

D. nodeSelector:
region: us-west
disktype: ssd

Solution

1. Step 1: Understand nodeSelector format for multiple labels

   nodeSelector is a map of key-value pairs, each on its own line with proper indentation.

2. Step 2: Evaluate each option's syntax

   nodeSelector: region: us-west disktype: ssd correctly lists two key-value pairs. nodeSelector: region: us-west, disktype: ssd uses invalid comma syntax. nodeSelector: - region=us-west - disktype=ssd uses list syntax which is invalid. nodeSelector: region=us-west disktype=ssd uses equals signs incorrectly.

3. Final Answer:

   nodeSelector: region: us-west disktype: ssd -> Option D

4. Quick Check:

   Multiple labels in nodeSelector use separate key: value lines [OK]

Hint: List each label as key: value pair under nodeSelector [OK]

Common Mistakes:

• Using commas to separate labels
• Using list syntax instead of map
• Using equals signs instead of colon in YAML