Cluster upgrade strategies in Kubernetes - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to upgrade the Kubernetes control plane to version 1.26.0.

Kubernetes

kubectl [1] cluster-version --version=1.26.0

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

Aapply

Bset

Crollout

Dupgrade

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'apply' instead of 'upgrade' causes an error because 'apply' is for resources.

Using 'set' or 'rollout' does not upgrade the cluster version.

The kubectl upgrade command is used to upgrade the Kubernetes cluster version.

2fill in blank

medium

Complete the command to drain a node named 'worker-1' before upgrading.

Kubernetes

kubectl drain [1] --ignore-daemonsets --delete-local-data

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

Aworker-1

Bmaster-1

Cnode-0

Dcontrol-plane

Attempts:

3 left

💡 Hint

Common Mistakes

Draining the control-plane node first can disrupt the cluster.

Using a wrong node name causes the command to fail.

Draining the node named worker-1 safely evicts pods before upgrade.

3fill in blank

hard

Fix the error in the command to upgrade a node using kubeadm.

Kubernetes

kubeadm upgrade node [1]

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

Aapply

Bplan

Cconfig

Dexec

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'apply' directly without planning can cause issues.

Using 'exec' or 'config' are invalid subcommands here.

The kubeadm upgrade node plan command shows the upgrade plan for the node.

4fill in blank

hard

Fill both blanks to create a command that cordons and drains a node named 'node-2'.

Kubernetes

kubectl [1] node-2 && kubectl [2] node-2 --ignore-daemonsets --delete-local-data

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

Acordon

Bdrain

Cuncordon

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'uncordon' first allows scheduling, which is wrong here.

Using 'delete' removes the node instead of preparing it for upgrade.

First, cordon marks the node unschedulable. Then, drain evicts pods safely.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps node names to their upgrade status if status is 'pending'.

Kubernetes

upgrade_status = [1]: [2] for [3], status in nodes.items() if status == 'pending'}

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

Anode

Bstatus

Dstate

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'state' instead of 'status' causes a NameError.

Mixing variable names inconsistently breaks the comprehension.

This comprehension creates a dictionary with node names as keys and their status as values, filtering only 'pending' statuses.

Practice

1. What is the recommended order when upgrading a Kubernetes cluster?

easy

A. Upgrade all nodes simultaneously

B. Upgrade worker nodes first, then control plane nodes

C. Upgrade control plane nodes first, then worker nodes

D. Upgrade only the worker nodes

Solution

1. Step 1: Understand the role of control plane nodes

   Control plane nodes manage the cluster state and API server, so they must be stable first.

2. Step 2: Upgrade worker nodes after control plane

   Worker nodes run workloads and depend on the control plane, so upgrade them after control plane nodes.

3. Final Answer:

   Upgrade control plane nodes first, then worker nodes -> Option C

4. Quick Check:

   Control plane first, workers second = A [OK]

Hint: Always upgrade control plane nodes before worker nodes [OK]

Common Mistakes:

• Upgrading worker nodes before control plane
• Upgrading all nodes at once causing downtime
• Skipping control plane upgrade

2. Which command correctly drains a node before upgrading it?

easy

A. kubectl drain --ignore-daemonsets --delete-local-data

B. kubectl upgrade node

C. kubectl delete node

D. kubectl cordon --force

Solution

1. Step 1: Identify the correct drain command syntax

   The command to safely evict pods is 'kubectl drain' with flags to ignore daemonsets and delete local data.

2. Step 2: Verify other options are incorrect

   Upgrade and delete commands do not drain nodes; cordon only marks unschedulable but does not evict pods.

3. Final Answer:

   kubectl drain <node-name> --ignore-daemonsets --delete-local-data -> Option A

4. Quick Check:

   Drain command with correct flags = A [OK]

Hint: Use 'kubectl drain' with flags to safely evict pods [OK]

Common Mistakes:

• Using 'kubectl cordon' instead of 'drain'
• Deleting nodes instead of draining
• Missing flags causing pod eviction failure

3. Given this upgrade sequence, what is the expected cluster state?

1. Drain node1
2. Upgrade node1
3. Uncordon node1
4. Repeat for node2 and node3

medium

A. Control plane nodes are upgraded last

B. Cluster remains available with minimal downtime

C. Pods are deleted permanently during upgrade

D. Cluster goes down during node upgrades

Solution

1. Step 1: Analyze the upgrade steps

   Each node is drained to safely evict pods, upgraded, then uncordoned to resume scheduling.

2. Step 2: Understand impact on cluster availability

   Upgrading nodes one by one with draining keeps workloads running on other nodes, minimizing downtime.

3. Final Answer:

   Cluster remains available with minimal downtime -> Option B

4. Quick Check:

   Draining and upgrading nodes one by one = D [OK]

Hint: Upgrade nodes one at a time with drain/un-cordon for uptime [OK]

Common Mistakes:

• Assuming cluster goes down during upgrades
• Not draining nodes causing pod failures
• Upgrading all nodes simultaneously

4. You ran kubectl drain node1 but pods did not evict. What is the likely cause?

medium

A. DaemonSet pods are blocking eviction

B. Node is already uncordoned

C. Control plane node cannot be drained

D. Pods have no local storage

Solution

1. Step 1: Understand drain behavior with DaemonSets

   By default, drain blocks if DaemonSet pods are running unless --ignore-daemonsets is used.

2. Step 2: Check other options for correctness

   Uncordon status does not block eviction; control plane nodes can be drained; pods without local storage do not block drain.

3. Final Answer:

   DaemonSet pods are blocking eviction -> Option A

4. Quick Check:

   DaemonSet pods block drain without flag = C [OK]

Hint: Use --ignore-daemonsets flag to drain nodes with DaemonSet pods [OK]

Common Mistakes:

• Not using --ignore-daemonsets flag
• Confusing cordon with drain
• Assuming control plane nodes cannot be drained

5. You want to upgrade a large Kubernetes cluster with minimal downtime. Which strategy is best?

hard

A. Upgrade all control plane nodes simultaneously, then all workers simultaneously

B. Skip draining and upgrade nodes in random order

C. Drain all nodes at once, upgrade, then uncordon all nodes

D. Use cloud provider upgrade tools to upgrade control plane, then drain and upgrade workers one by one

Solution

1. Step 1: Consider cloud provider tools for control plane upgrade

   Cloud tools often automate safe control plane upgrades reducing manual errors.

2. Step 2: Upgrade worker nodes one by one with drain/un-cordon

   This approach avoids downtime by keeping workloads running on other nodes during upgrade.

3. Step 3: Evaluate other options for risks

   Upgrading all nodes simultaneously or skipping drain risks downtime and pod failures.

4. Final Answer:

   Use cloud provider upgrade tools to upgrade control plane, then drain and upgrade workers one by one -> Option D

5. Quick Check:

   Cloud tools + sequential worker upgrade = B [OK]

Hint: Use cloud tools and upgrade workers one at a time with drain [OK]

Common Mistakes:

• Upgrading all nodes simultaneously causing downtime
• Skipping drain causing pod disruption
• Ignoring cloud provider upgrade features