The answer is that the customer is responsible for patching the guest OS in IaaS VMs. This is correct because under the shared responsibility model for IaaS, the cloud provider secures the physical datacenter, network, and hypervisor, while the customer manages everything they deploy on top of that abstracted infrastructure—including the guest operating system, applications, and data. On the Microsoft Azure Fundamentals AZ-900 exam, this concept tests your understanding of where provider responsibility ends and customer responsibility begins; a common trap is assuming the provider handles all OS updates since they manage the host. Remember the memory tip: in IaaS, you control the “guest” (the OS inside the VM), so you patch it—the provider only patches the “host” (the hypervisor and physical hardware).
AZ-900 Describe cloud concepts Practice Question
This AZ-900 practice question tests your understanding of describe cloud concepts. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Which of the following best describes the 'shared responsibility' for operating system updates under the IaaS model?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The customer is responsible for patching the guest OS in IaaS VMs
Under the Infrastructure as a Service (IaaS) model, the cloud provider is responsible for the physical infrastructure and the hypervisor, but the customer retains control over the guest operating system running inside the virtual machine. Therefore, the customer is responsible for patching and updating the guest OS, including applying security updates and managing configuration. This aligns with the shared responsibility model where the customer manages anything they deploy on top of the abstracted infrastructure.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The cloud provider is responsible for patching the OS in IaaS VMs
Why it's wrong here
In IaaS, OS patching is the customer's responsibility; the provider only manages hypervisor and hardware.
✓
The customer is responsible for patching the guest OS in IaaS VMs
Why this is correct
In IaaS, customers must patch and maintain the guest OS; the provider manages physical infrastructure and hypervisor.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Both customer and provider share equal responsibility for OS patches in IaaS
Why it's wrong here
OS patching in IaaS is entirely the customer's responsibility — not shared equally.
✗
OS patching is not required in cloud environments as Azure handles this automatically
Why it's wrong here
Azure handles OS patching automatically only in PaaS/SaaS; IaaS customers must manage it themselves.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume the cloud provider handles all security updates, confusing IaaS with PaaS or SaaS where the provider does manage the OS, leading them to incorrectly select option A or D.
Detailed technical explanation
How to think about this question
In Azure IaaS, the hypervisor (e.g., Hyper-V) isolates the VM from the host, and the provider patches the host OS and firmware. The guest OS, however, runs its own kernel and services, so the customer must apply patches (e.g., via Windows Update or apt) to address vulnerabilities like CVE-2023-23397. This separation is critical in multi-tenant environments where a compromised guest OS could affect only that VM, not the host or other tenants.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-900 question in full detail.
Describe cloud concepts — This question tests Describe cloud concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The customer is responsible for patching the guest OS in IaaS VMs — Under the Infrastructure as a Service (IaaS) model, the cloud provider is responsible for the physical infrastructure and the hypervisor, but the customer retains control over the guest operating system running inside the virtual machine. Therefore, the customer is responsible for patching and updating the guest OS, including applying security updates and managing configuration. This aligns with the shared responsibility model where the customer manages anything they deploy on top of the abstracted infrastructure.
What should I do if I get this AZ-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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