Creating a VM in Azure Portal - Performance & Efficiency

Time Complexity: Creating a VM using Azure CLI

O(n)

Understanding Time Complexity

When creating a virtual machine (VM) using Azure CLI, it is important to understand how the time to complete the process changes as you create more VMs.

We want to know how the number of steps and operations grows when adding more VMs.

Scenario Under Consideration

Analyze the time complexity of the following operation sequence.

# Create a resource group
az group create --name MyResourceGroup --location eastus

# Create a virtual machine
az vm create --resource-group MyResourceGroup --name MyVM --image UbuntuLTS --admin-username azureuser --generate-ssh-keys

# Repeat VM creation for multiple VMs
for i in range(1, n+1):
  az vm create --resource-group MyResourceGroup --name MyVM$i --image UbuntuLTS --admin-username azureuser --generate-ssh-keys

This sequence creates a resource group once, then creates multiple VMs one by one inside that group.

Identify Repeating Operations

Identify the API calls, resource provisioning, data transfers that repeat.

• Primary operation: VM creation API call for each VM.
• How many times: Once for the resource group, then n times for each VM.

How Execution Grows With Input

Each VM creation requires a separate API call and provisioning process, so the total time grows as you add more VMs.

Input Size (n)	Approx. Api Calls/Operations
10	1 (resource group) + 10 (VMs) = 11
100	1 + 100 = 101
1000	1 + 1000 = 1001

Pattern observation: The number of operations grows directly with the number of VMs created.

Final Time Complexity

Time Complexity: O(n)

This means the time to create VMs grows linearly with the number of VMs you want to create.

Common Mistake

[X] Wrong: "Creating multiple VMs at once takes the same time as creating one VM."

[OK] Correct: Each VM requires its own setup and resources, so time adds up with each VM.

Interview Connect

Understanding how operations scale helps you plan cloud resources and estimate deployment times in real projects.

Self-Check

"What if we used a VM scale set instead of creating individual VMs? How would the time complexity change?"

Practice

1. What is the first step when creating a Virtual Machine (VM) in the Azure Portal?

easy

A. Choose the VM name and region

B. Connect to the VM using SSH

C. Select the VM size after creation

D. Install software on the VM

Solution

1. Step 1: Start VM creation in Azure Portal

   When creating a VM, you first open the Azure Portal and start the 'Create a virtual machine' process.

2. Step 2: Enter basic details like name and region

   The first required details are the VM's name and the region where it will be hosted.

3. Final Answer:

   Choose the VM name and region -> Option A

4. Quick Check:

   First step is naming and region selection [OK]

Hint: Name and region come first when creating a VM [OK]

Common Mistakes:

• Trying to connect before VM is created
• Selecting size before naming VM
• Installing software before VM setup

2. Which option correctly describes the step to select the operating system image when creating a VM in Azure Portal?

easy

A. Skip image selection; Azure picks automatically

B. Choose the image after VM creation

C. Upload your own OS image only

D. Select the image during VM setup under 'Image' section

Solution

1. Step 1: Locate the 'Image' section in VM creation

   During VM setup, there is a section called 'Image' where you select the OS image.

2. Step 2: Select a predefined OS image

   You pick from available images like Windows Server or Ubuntu Linux before creating the VM.

3. Final Answer:

   Select the image during VM setup under 'Image' section -> Option D

4. Quick Check:

   Image selection happens during setup [OK]

Hint: Pick OS image during VM setup, not after [OK]

Common Mistakes:

• Thinking image is chosen after VM is created
• Assuming Azure picks image automatically
• Believing you must upload your own image

3. After creating a Linux VM in Azure Portal, which method is used to connect to it?

medium

A. Remote Desktop Protocol (RDP)

B. SSH (Secure Shell)

C. FTP (File Transfer Protocol)

D. HTTP (Hypertext Transfer Protocol)

Solution

1. Step 1: Identify the OS type of the VM

   The VM is Linux-based, which typically uses SSH for secure command-line access.

2. Step 2: Use SSH to connect

   SSH is the standard protocol to connect securely to Linux VMs remotely.

3. Final Answer:

   SSH (Secure Shell) -> Option B

4. Quick Check:

   Linux VM connection uses SSH [OK]

Hint: Linux VMs connect via SSH, Windows via RDP [OK]

Common Mistakes:

• Trying to use RDP on Linux VM
• Using FTP or HTTP to connect to VM
• Confusing protocols for connection

4. You created a Windows VM but cannot connect using Remote Desktop. What is the most likely cause?

medium

A. Network security group (NSG) blocks RDP port 3389

B. The VM size is too small

C. You selected a Linux image by mistake

D. The VM name is invalid

Solution

1. Step 1: Check network security settings

   Remote Desktop uses port 3389, which must be allowed in the VM's network security group (NSG).

2. Step 2: Identify blocked port issue

   If NSG blocks port 3389, RDP connections fail even if VM is running.

3. Final Answer:

   Network security group (NSG) blocks RDP port 3389 -> Option A

4. Quick Check:

   Blocked RDP port causes connection failure [OK]

Hint: Open port 3389 in NSG for Windows VM RDP [OK]

Common Mistakes:

• Assuming VM size affects RDP connection
• Confusing OS image type after creation
• Thinking VM name affects connectivity

5. You want to create a VM in Azure Portal that can be accessed securely from anywhere. Which combination of settings is best?

hard

A. Use a Linux VM, use password authentication, block all inbound ports

B. Use a Windows VM, use password authentication, open port 3389 to all IPs

C. Use a Linux VM, select SSH key authentication, open port 22 in NSG

D. Use a Windows VM, disable NSG, connect via RDP

Solution

1. Step 1: Choose secure authentication method

   SSH key authentication is more secure than passwords for Linux VMs.

2. Step 2: Open only necessary port in NSG

   Opening port 22 for SSH allows secure remote access; avoid opening unnecessary ports.

3. Step 3: Avoid insecure options

   Opening RDP port 3389 to all IPs or disabling NSG reduces security.

4. Final Answer:

   Use a Linux VM, select SSH key authentication, open port 22 in NSG -> Option C

5. Quick Check:

   SSH key + port 22 open = secure access [OK]

Hint: Use SSH keys and open only port 22 for secure Linux VM access [OK]

Common Mistakes:

• Using password authentication over SSH
• Opening RDP port to all IPs
• Disabling NSG for convenience