Azure Virtual Machines – Interview Q&A

1. Azure VM Fundamentals

Q1. What is an Azure Virtual Machine?

Answer: Azure VM is an Infrastructure as a Service (IaaS) offering that provides virtual Windows or Linux servers in the cloud.

Key Points: Full OS control, scalable compute, pay-as-you-go pricing.

Q2. Why do we use Azure Virtual Machines?

Answer: Azure VMs are used to host applications, databases, development environments, and legacy systems without maintaining physical servers.

Key Points: Flexibility, OS customization, infrastructure management.

Q3. Is Azure VM IaaS, PaaS, or SaaS?

Answer: Azure VM is IaaS because Azure manages the physical infrastructure while customers manage the guest OS, applications, and configurations.

Key Points: Microsoft manages hardware; customers manage OS and software.

Q4. What is the difference between Azure VM and Azure App Service?

Key Point: Choose VM when OS-level control is required.

Q5. What is a Hypervisor in Azure?

Answer: A hypervisor is virtualization software that allows multiple isolated virtual machines to run on the same physical server.

Key Points: Resource allocation, VM isolation, virtualization.

2. Azure VM Sizes and Series

Q6. What are Azure VM sizes?

Answer: VM sizes define the available vCPUs, RAM, storage capabilities, and network performance.

Key Points: Select based on workload, performance, and cost.

Q7. What are the important Azure VM series?

Q8. What is B-Series in Azure VM?

Answer: B-Series VMs provide burstable CPU performance using CPU credits. They are suitable for workloads with low average CPU usage and occasional spikes.

Key Points: CPU credits, development, lightweight applications.

Q9. Which VM series is suitable for ASP.NET Core applications?

Answer: D-Series is commonly suitable for production ASP.NET Core applications because it balances CPU and memory.

Key Points: General purpose, web applications, REST APIs.

Q10. What does Standard_D2s_v3 mean?

Answer: D represents the general-purpose family, 2 indicates two vCPUs, s indicates Premium Storage support, and v3 identifies the generation.

Key Points: VM family, vCPU count, storage capability, generation.

3. Azure VM Pricing

Q11. What are the different Azure VM pricing models?

Answer: The main options are Pay-As-You-Go, Reserved VM Instances, and Spot VMs.

Key Points: Flexible pricing, committed discounts, interruptible capacity.

Q12. What is Pay-As-You-Go pricing?

Answer: Pay-As-You-Go charges for compute usage without requiring a long-term commitment.

Key Points: Development, testing, unpredictable workloads.

Q13. What are Azure Reserved VM Instances?

Answer: Reserved VM Instances provide discounted compute pricing through one-year or three-year commitments.

Key Points: Predictable workloads, long-term savings, billing discount.

Q14. What is an Azure Spot VM?

Answer: Spot VMs use unused Azure compute capacity at discounted rates. Azure can evict them when capacity is required or pricing conditions are met.

Key Points: Batch processing, testing, fault-tolerant workloads.

Q15. What is Azure Hybrid Benefit?

Answer: Azure Hybrid Benefit allows eligible organizations to use existing Windows Server or SQL Server licenses to reduce Azure costs.

Key Points: License reuse, cost optimization, eligibility requirements.

4. Azure VM Storage

Q16. What is Azure Managed Disk?

Answer: Azure Managed Disk provides persistent block storage for VMs, with Azure managing the underlying storage infrastructure.

Key Points: OS disks, data disks, managed storage.

Q17. What are the types of disks in Azure VMs?

Answer: The three main disk categories are OS Disk, Data Disk, and Temporary Disk.

Key Points: OS storage, persistent application data, temporary files.

Q18. What is the difference between OS Disk, Data Disk, and Temporary Disk?

Q19. What are the Azure Managed Disk performance tiers?

Answer: Standard HDD, Standard SSD, Premium SSD, Premium SSD v2, and Ultra Disk provide different performance and cost options.

Key Points: IOPS, throughput, latency, workload requirements.

Q20. What is IOPS in Azure Disk?

Answer: IOPS stands for Input/Output Operations Per Second. It measures how many read and write operations a disk can handle per second.

Key Points: Disk performance, database workloads, storage optimization.

5. Azure VM Networking

Q21. What is a Virtual Network (VNet)?

Answer: A VNet is a logically isolated network in Azure that allows VMs and other resources to communicate securely.

Key Points: Private networking, subnets, network isolation.

Q22. What is the difference between Public IP and Private IP?

Answer: A Public IP provides internet-reachable addressing, while a Private IP enables communication within a VNet and connected private networks.

Key Points: Public IP – Internet; Private IP – internal communication.

Q23. What is a Network Security Group (NSG)?

Answer: An NSG controls inbound and outbound network traffic using rules based on IP addresses, protocols, and ports.

Key Points: Allow/Deny rules, priority, subnet/NIC association.

Q24. How does NSG rule priority work?

Answer: NSG rules are evaluated by priority, with lower numbers taking precedence. Once traffic matches a rule, that rule's action is applied.

Key Points: Priority 100 precedes 200; NSGs are stateful.

Q25. What are the important Azure VM network ports?

Q26. What is Azure Bastion?

Answer: Azure Bastion provides secure SSH and RDP connectivity to VMs without requiring public IP addresses on those VMs.

Key Points: Secure remote access, private VM connectivity.

6. Azure VM Deployment and Remote Access

Q27. How do you create an Azure VM?

Answer: Open Azure Portal → Virtual Machines → Create → Select resource group, image, VM size, authentication, disks, and networking → Review + Create.

Key Points: Resource group, image, size, NSG, disk configuration.

Q28. What is an Azure VM Image?

Answer: A VM image is a template containing an operating system and optionally preinstalled software used to create virtual machines.

Key Points: Windows, Ubuntu, Azure Marketplace, custom images.

Q29. How do you connect to a Linux VM?

Answer: Use SSH with the VM's reachable IP address or DNS name and the appropriate credentials.

ssh -i privatekey.pem azureuser@PUBLIC_IP

Key Points: SSH, port 22, private key authentication.

Q30. How do you connect to a Windows VM?

Answer: Use Remote Desktop Protocol (RDP) through a permitted network path, providing the VM address and valid Windows credentials.

mstsc

Key Points: RDP, TCP 3389, Windows authentication.

Q31. What is the difference between SSH and RDP?

Q32. Can ASP.NET Core applications run on Linux Azure VMs?

Answer: Yes. ASP.NET Core is cross-platform and can run on Linux using Kestrel, commonly behind Nginx as a reverse proxy.

Key Points: Linux hosting, Kestrel, Nginx, HTTPS.

Q33. How do you host ASP.NET Core on a Windows VM?

Answer: Install IIS and the .NET Hosting Bundle, publish the application, configure an IIS website, and allow the required network traffic.

Key Points: IIS, .NET Hosting Bundle, application deployment.

7. Azure VM Lifecycle and Cost

Q34. What is the difference between Stopped and Deallocated?

Key Point: Deallocation stops normal VM compute billing, but disks and other resources may still incur charges.

Q35. Does shutting down a VM inside Windows or Linux stop Azure billing?

Answer: Not necessarily. Guest OS shutdown typically leaves the VM allocated, so compute charges can continue.

Key Points: Use Azure Portal Stop and verify deallocation.

Q36. What is Auto-Shutdown in Azure VM?

Answer: Auto-Shutdown automatically stops and deallocates a VM at a configured time to reduce unnecessary compute costs.

Key Points: Development environments, scheduled shutdown, cost savings.

Q37. How can you reduce Azure VM costs?

Answer: Right-size VMs, deallocate unused machines, use reservations for predictable workloads, and use Spot VMs for interruptible tasks.

Key Points: Auto-shutdown, Azure Advisor, budgets, disk cleanup.

8. Azure VM Security and Monitoring

Q38. How do you secure an Azure VM?

Answer: Restrict management ports, use Azure Bastion, enable backups, apply OS patches, and enforce least-privilege access.

Key Points: NSG, RBAC, encryption, SSH keys, monitoring.

Q39. What is Azure Monitor for VMs?

Answer: Azure Monitor collects and analyzes VM performance metrics and diagnostic data to help identify operational issues.

Key Points: CPU, memory with guest monitoring, disk, network, alerts.

Q40. What is Boot Diagnostics?

Answer: Boot Diagnostics helps troubleshoot VM startup problems by providing boot screenshots and serial console logs.

Key Points: Startup failures, troubleshooting, diagnostic logs.

9. Important Real-Time Scenario Questions

Q41. Your Azure VM is running, but you cannot connect through RDP. What will you check?

Answer: Check the VM's IP and connectivity, NSG port 3389, Windows Firewall, RDP service, credentials, and VM health.

Key Points: NSG, firewall, network routing, RDP.

Q42. Your Linux VM is not accessible through SSH. How will you troubleshoot?

Answer: Verify VM status, network connectivity, NSG port 22, SSH service, username, private key, and guest firewall.

Key Points: SSH configuration, NSG, authentication.

Q43. Your application is running on an Azure VM but is not accessible through a browser. What will you check?

Answer: Verify that the application is listening, the web server is running, and NSG/firewall rules permit HTTP or HTTPS traffic.

Key Points: Port 80/443, IIS/Nginx, DNS, application binding.

Q44. Your VM CPU utilization is consistently above 90%. What will you do?

Answer: Investigate the high-CPU processes, optimize the workload, and resize the VM if more capacity is required.

Key Points: Azure Monitor, performance analysis, vertical scaling.

Q45. A development VM is required only during office hours. How will you optimize costs?

Answer: Configure automatic deallocation after office hours and schedule startup when required.

Key Points: Auto-shutdown, automation, compute savings.

Q46. Your VM needs additional storage without replacing the OS disk. What will you do?

Answer: Attach a managed data disk, initialize and format it, and mount it in Linux or assign a drive letter in Windows.

Key Points: Data disk, persistent storage, disk management.

Q47. Can you resize an existing Azure VM?

Answer: Yes. Azure supports resizing to compatible VM sizes, subject to regional capacity and hardware constraints. A restart or deallocation may be necessary.

Key Points: Vertical scaling, vCPU, RAM, possible downtime.

Q48. What happens when you delete an Azure VM?

Answer: The VM compute resource is deleted, but disks, NICs, public IPs, and other associated resources may remain depending on deletion settings.

Key Points: Resource cleanup, delete options, remaining costs.

Q49. How do you provide high availability for an Azure VM application?

Answer: Deploy multiple VM instances across Availability Zones or appropriate availability configurations and distribute traffic using a load balancer.

Key Points: Redundancy, fault tolerance, load balancing.

Q50. Which is better for hosting an ASP.NET Core Web API: Azure VM or App Service?

Answer: App Service is generally preferable when managed web hosting is sufficient. Choose Azure VM when the application requires OS-level control or custom server dependencies.

Key Points: PaaS vs IaaS, maintenance responsibility, application requirements.