Why VM commands (create, start, stop) in Azure? - Purpose & Use Cases

The Big Idea

What if you could create and control cloud computers with just a few simple commands?

The Scenario

Imagine you want to set up a computer in the cloud to run your app. You open the cloud website, click many buttons to create the computer, wait for it to appear, then find the start and stop buttons to control it.

Doing this for many computers or often means repeating these slow steps again and again.

The Problem

Manually clicking takes a lot of time and can cause mistakes, like starting the wrong computer or forgetting to stop one, which wastes money.

It's hard to keep track of many computers this way, and you can't easily repeat the same setup exactly.

The Solution

Using simple commands to create, start, and stop virtual machines lets you do these tasks quickly and correctly every time.

You can write these commands once and run them whenever you want, saving time and avoiding errors.

Before vs After

✗ Before

Go to portal > Create VM > Fill form > Click start > Click stop

✓ After

az vm create ...
az vm start ...
az vm stop ...

What It Enables

You can manage many virtual machines easily and reliably with just a few commands.

Real Life Example

A developer needs to test software on different computers. Instead of clicking around, they run commands to create and start the needed machines quickly, then stop them when done to save costs.

Key Takeaways

Manual VM management is slow and error-prone.

Commands automate creation and control of VMs.

This saves time, reduces mistakes, and controls costs.

Practice

1. What does the az vm create command do in Azure?

easy

A. It starts an existing virtual machine.

B. It stops a running virtual machine.

C. It creates a new virtual machine in Azure.

D. It deletes a virtual machine.

Solution

1. Step 1: Understand the command purpose

   The az vm create command is used to make a new virtual machine in Azure.

2. Step 2: Compare with other commands

   az vm start starts a VM, az vm stop stops it, and az vm delete removes it.

3. Final Answer:

   It creates a new virtual machine in Azure. -> Option C

4. Quick Check:

   az vm create = create VM [OK]

Hint: Create means make new VM, start means turn on, stop means turn off [OK]

Common Mistakes:

• Confusing create with start or stop commands
• Thinking create also starts the VM automatically
• Mixing stop with delete

2. Which of the following is the correct syntax to start a VM named myVM in resource group myGroup?

easy

A. az vm create --name myVM --resource-group myGroup

B. az vm start --name myVM --resource-group myGroup

C. az vm stop --name myVM --resource-group myGroup

D. az vm delete --name myVM --resource-group myGroup

Solution

1. Step 1: Identify the command to start a VM

   The command to start a VM is az vm start.

2. Step 2: Check the syntax for name and resource group

   The correct flags are --name for VM name and --resource-group for the group.

3. Final Answer:

   az vm start --name myVM --resource-group myGroup -> Option B

4. Quick Check:

   Start VM syntax = az vm start [OK]

Hint: Start VM uses 'az vm start' with --name and --resource-group [OK]

Common Mistakes:

• Using create instead of start to power on VM
• Forgetting to specify resource group
• Using stop or delete commands by mistake

3. What will happen if you run this command?

az vm stop --name testVM --resource-group testGroup

medium

A. The VM named testVM will be stopped (powered off).

B. The VM named testVM will be deleted.

C. The VM named testVM will be started.

D. The command will show a syntax error.

Solution

1. Step 1: Understand the command action

   az vm stop stops (powers off) the specified VM.

2. Step 2: Confirm the VM and resource group names

   The VM name is testVM and resource group is testGroup, both valid inputs.

3. Final Answer:

   The VM named testVM will be stopped (powered off). -> Option A

4. Quick Check:

   az vm stop = stop VM [OK]

Hint: Stop command powers off VM, does not delete or start it [OK]

Common Mistakes:

• Confusing stop with delete
• Thinking stop starts the VM
• Assuming syntax error due to names

4. You tried to start a VM with this command:

az vm start -n myVM -g myGroup

The command failed with an error. What is the likely cause?

medium

A. The VM name or resource group might be misspelled or does not exist.

B. You must stop the VM before starting it.

C. The flags -n and -g are incorrect; use full names instead.

D. The az vm start command cannot use short flags.

Solution

1. Step 1: Check command flags

   -n and -g are valid short forms for --name and --resource-group.

2. Step 2: Consider common errors

   Errors usually happen if the VM or resource group name is wrong or missing in Azure.

3. Final Answer:

   The VM name or resource group might be misspelled or does not exist. -> Option A

4. Quick Check:

   Invalid names cause start errors, not flags [OK]

Hint: Check VM and group names carefully if start fails [OK]

Common Mistakes:

• Assuming short flags are invalid
• Thinking VM must be stopped before starting
• Confusing start errors with syntax errors

5. You want to save money by stopping a VM but keep its data intact. Which command should you use and why?

hard

A. Use az vm stop because it powers off the VM but keeps the disk data.

B. Use az vm delete because it stops and removes the VM and data.

C. Use az vm restart because it stops and starts the VM quickly.

D. Use az vm deallocate because it stops the VM and releases compute resources but keeps data.

Solution

1. Step 1: Understand stopping vs deallocating

   az vm stop powers off the VM but does not release compute resources, so charges continue.

2. Step 2: Identify the command to save costs

   az vm deallocate stops the VM and releases compute resources, saving money while keeping disk data.

3. Final Answer:

   Use az vm deallocate because it stops the VM and releases compute resources but keeps data. -> Option D

4. Quick Check:

   Deallocate = stop + release resources + keep data [OK]

Hint: Deallocate stops VM and saves cost without deleting data [OK]

Common Mistakes:

• Using stop only and expecting cost savings
• Deleting VM to save money loses data
• Restarting does not save costs