Exam SC-100 topic 1 question 28 discussion

Actual exam question from Microsoft's SC-100

Question #: 28
Topic #: 1

You have an Azure Kubernetes Service (AKS) cluster that hosts Linux nodes.

You need to recommend a solution to ensure that deployed worker nodes have the latest kernel updates. The solution must minimize administrative effort.

What should you recommend?

A. The nodes must restart after the updates are applied.
B. The updates must first be applied to the image used to provision the nodes.
C. The AKS cluster version must be upgraded.

Show Suggested Answer

Suggested Answer: B 🗳️

by Victory007 at Aug. 5, 2023, 6:34 p.m.

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SFAY

Highly Voted 9 months, 4 weeks ago

Selected Answer: B

B is the correct answer. Microsoft creates a new node image for AKS nodes approximately once per week. A node image contains up-to-date OS security patches, OS kernel updates, Kubernetes security updates, updated versions of binaries like kubelet, and component version updates that are listed in the release notes. When a node image is updated, a cordon and drain action is triggered on the target node pool's nodes: A node with the updated image is added to the node pool. The number of nodes added at a time is governed by the surge value. One of the existing nodes is cordoned and drained. Cordoning ensures that the node doesn't schedule pods. Draining removes its pods and schedules them to other nodes. After the node is fully drained, it's removed from the node pool. The updated node added by the surge replaces it. This process is repeated for each node that needs to be updated in the node pool. A similar process occurs during a cluster upgrade. Source: https://learn.microsoft.com/en-us/azure/architecture/operator-guides/aks/aks-upgrade-practices

upvoted 7 times

lt9898

9 months, 3 weeks ago

I now agree with SFAY that it seems like the ideal solution (least admin overhead) would be to leverage 'cordon and drain' via the automated NodeImage update channel and configure an aksManagedNodeosUpgradeSchedule maintenance window. Thanks for sharing the link. A - No, although this functionality is still supported by the 'unmanaged' update channel, there is now a better solution to minimise admin overhead than leveraging Kured to faciliate an in-place update B - Yes, we need to ensure the image used to provision the node had been updated (despite it being automatic now). However, agree with SFAY that i'd probably pick this if forced as it's closest. C - No, the cluster version never needs updating for this Seems there's no way to update my previous answer below...

upvoted 2 times

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PierreTang

Most Recent 10 months ago

Selected Answer: A

Lt9898

upvoted 1 times

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lt9898

10 months ago

Selected Answer: A

Hang on, why is everybody favouring selecting the image before provision of the node? That was my original choice without reading then I found the page below published 20/4/2023. https://learn.microsoft.com/en-us/azure/aks/node-updates-kured "To protect your clusters, security updates are automatically applied to Linux nodes in AKS. These updates include OS security fixes or kernel updates. Some of these updates require a node reboot to complete the process. AKS doesn't automatically reboot these Linux nodes to complete the update process. ... This article shows you how to use the open-source kured (KUbernetes REboot Daemon) to watch for Linux nodes that require a reboot, then automatically handle the rescheduling of running pods and node reboot process"

upvoted 2 times

lt9898

9 months, 3 weeks ago

Switching to B although I can't edit my initial vote. SFAY shared the more recently updated page that outlines the automated update process via the weekly image updates published by MS. If the requirements said that we need to stay up to date to the day, then i'd consider Kured to apply the nightly updates available via the 'Unmanaged' update channel

upvoted 1 times

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cris_exam

10 months ago

I tend to be convinced by your finding and also add this extra bit from the same page. "Some security updates, such as kernel updates, require a node reboot to finalize the process." "You can use your own workflows and processes to handle node reboots, or use kured to orchestrate the process." So, reboot seems to be required but these could be configured to happen orchestrated to minimize admin effort. https://learn.microsoft.com/en-us/azure/aks/node-updates-kured#understand-the-aks-node-update-experience

upvoted 1 times

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