Exercise - Add a data disk to a VM

10 minutes

Your law firm is expanding its case load, and you're tasked with creating a new Linux web server to store critical documents from various sources: clients, other law firms, and law-enforcement offices. The web server lets you upload documents and store them on disk.

Tip

This exercise uses Linux as the example, but the basic process of creating VMs and adding disks is the same for Windows. The primary difference would be in partitioning and formatting the disk. On Windows, you can connect to your VM over Remote Desktop and use the built-in Disk Management tools or deploy a PowerShell script that's similar to the Bash script you'll use here.

Your goal is to create a Linux VM and attach a new virtual hard disk (VHD) named uploadDataDisk1 to store the /uploads directory.

Set Azure CLI default values

The Azure CLI lets you set default values so you don't have to repeat them each time you run a command.

You specify the default Azure location, or region. This location is where your Azure VM is placed.

Ideally, this location is close to your clients. In this case, select the closest region to you from the locations available to the Azure sandbox.

The free sandbox allows you to create resources in a subset of the Azure global regions. Select a region from this list when you create resources:

westus2
southcentralus
centralus
eastus
westeurope

southeastasia
japaneast
brazilsouth
australiasoutheast
centralindia

Run az configure to set the default location you want to use. Replace eastus with the location chosen in the previous step.
```
az configure --defaults location=eastus
```
Tip

You can use the Copy button to copy commands to the clipboard. To paste, right-click on a new line in the Cloud Shell terminal and select Paste, or use the Shift+Insert keyboard shortcut (⌘+V on macOS).
Set the default resource group name to the preconfigured resource group created for you through the Azure sandbox: [sandbox resource group]
```
az configure --defaults group="<rgn>[sandbox Resource Group]</rgn>"
```

Create a Linux VM

Here, you create a Linux VM to host your web server.

Run this az vm create command to create an Ubuntu Linux VM.
```
az vm create \
  --name support-web-vm01 \
  --image Canonical:UbuntuServer:16.04-LTS:latest \
  --size Standard_DS1_v2 \
  --admin-username azureuser \
  --generate-ssh-keys
```
- The VM's name is support-web-vm01.
- Its size is Standard_DS1_v2.
- The admin username is azureuser. In practice, this name can be whatever you like.
- The --generate-ssh-keys argument generates an SSH keypair for you, allowing you to connect to your VM over SSH.
The VM takes a few minutes to deploy. When the VM is ready, you see information about it in JSON format. Here's an example:
```
{
  "fqdns": "",
  "id": "/subscriptions/00000000-0000-0000-0000-000000000000/resourceGroups/680469d8-edB7-42ec-b118-cd80d51741e7/providers/Microsoft.Compute/virtualMachines/support-web-vm01",
  "location": "eastus",
  "macAddress": "00-0D-3A-10-63-0A",
  "powerState": "VM running",
  "privateIpAddress": "10.0.0.4",
  "publicIpAddress": "104.211.38.211",
  "resourceGroup": "680469d8-edB7-42ec-b118-cd80d51741e7",
  "zones": ""
}
```
Note

In this lesson, you're using this VM to learn how to manage disks. In practice, you might also install web server and other software and then run az vm open-port to make the ports you need available to the outside world.

Add an empty data disk to your VM

Here, you create an empty data disk and attach it to your VM. Initially, Your data disk is 64 GB in size. Later, you mount this disk to the /uploads directory on your VM.

Tip

For learning purposes, you're creating the VM and data disk as separate steps. In practice, you can specify the --data-disk-sizes-gb argument to the az vm create command to add data disks when the VM is created.

Run the following az vm disk attach command to add a new empty disk to the VM.
```
az vm disk attach \
  --vm-name support-web-vm01 \
  --name uploadDataDisk1 \
  --size-gb 64 \
  --sku Premium_LRS \
  --new
```
This command:
- Names the disk uploadDataDisk1.
- Sets its size to be 64 GB.
- Specifies the use of premium storage with local redundancy.

To use the disk, you need to partition and format it. Let's do that next.

Initialize and format your data disk

Your empty data drive needs to be initialized and formatted. The process to do that is the same as for a physical disk.

For one-time tasks, you might manually connect to your VM over SSH and run the commands you need. However, to make the process more repeatable and less error-prone, you can specify your commands in a Bash script or a PowerShell script (if it's available).

Using a script to automate the process has an added benefit: your script serves as documentation for how the process is performed. Others can read your script to understand how the system is configured. If you need to change the process, you can just modify your script and test it on a temporary scratch VM before you deploy your change to production.

To automate the process in this lesson, you use the Custom Script Extension. The Custom Script Extension is an easy way to download and run scripts on your Azure VMs. It's just one of the many ways you can configure the system after your VM is up and running.

You can store your scripts in Azure storage, or in a public location such as GitHub. You can run scripts manually or as part of a more automated deployment. Here, you run an Azure CLI command to download a premade Bash script from GitHub and execute it on your VM.

For learning purposes, let's also run a few commands on your VM to verify that the VM is configured as you expect.

Run az vm show to get your VM's public IP address and save the IP address as a Bash variable.

ipaddress=$(az vm show \
  --name support-web-vm01 \
  --show-details \
  --query [publicIps] \
  --output tsv)

Run the following ssh command to run the lsblk command on your VM over an SSH connection using the ipaddress variable data you created in the previous step. Recall that azureuser was the admin username we used when we created the VM. If you chose a different name, use that instead. Enter yes when prompted.
```
ssh azureuser@$ipaddress lsblk
```
The output of this command should look like the following.
```
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sdb       8:16   0    7G  0 disk 
└─sdb1    8:17   0    7G  0 part /mnt
sr0      11:0    1  628K  0 rom  
sdc       8:32   0   64G  0 disk 
sda       8:0    0   30G  0 disk 
├─sda14   8:14   0    4M  0 part 
├─sda15   8:15   0  106M  0 part /boot/efi
└─sda1    8:1    0 29.9G  0 part /
```
Notice that the 64-GB drive, sdc, you created isn't mounted. The drive is listed this way because it isn't initialized yet.
Run the following az vm extension set command to run the premade Bash script on your VM.

Warning

The script modifies /etc/fstab. Improperly modifying the /etc/fstab file could result in an unbootable system. Always test configuration changes on a temporary scratch system before you deploy to production. Refer to your distribution's documentation to learn how to properly modify this file. In production, we also recommend that you create a backup of this file so you can restore the configuration if needed.
```
az vm extension set \
  --vm-name support-web-vm01 \
  --name customScript \
  --publisher Microsoft.Azure.Extensions \
  --settings '{"fileUris":["https://raw.githubusercontent.com/MicrosoftDocs/mslearn-add-and-size-disks-in-azure-virtual-machines/master/add-data-disk.sh"]}' \
  --protected-settings '{"commandToExecute": "./add-data-disk.sh"}'
```
While the command runs, you can examine the Bash script from a separate browser tab, if you'd like.

To summarize, the script:
- Partitions the drive /dev/sdc.
- Creates an ext4 filesystem on the drive.
- Creates the /uploads directory, which we use as our mount point.
- Attaches the disk to the mount point.
- Updates /etc/fstab so that the drive is mounted automatically after the system reboots.

To verify the configuration, run the same ssh command as you did previously to run the lsblk command on your VM over an SSH connection.

ssh azureuser@$ipaddress lsblk

You see that sdc/sdc1 is partitioned and mounted to the /uploads directory as you expect.

NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sdb       8:16   0    7G  0 disk 
└─sdb1    8:17   0    7G  0 part /mnt
sr0      11:0    1  628K  0 rom  
sdc       8:32   0   64G  0 disk 
└─sdc1    8:33   0   64G  0 part /uploads
sda       8:0    0   30G  0 disk 
├─sda14   8:14   0    4M  0 part 
├─sda15   8:15   0  106M  0 part /boot/efi
└─sda1    8:1    0 29.9G  0 part /

Tip

Some Linux kernels support TRIM to discard unused blocks on disks. This feature is available on Azure disks and can save you money if you create large files and then delete them. Learn how to turn this feature on in the Azure documentation.

Summary

Here, you created a data disk and attached it to your VM. You used the Custom Script Extension to run a premade Bash script on your VM to make the process more repeatable. The Bash script partitions, formats, and mounts your disk so that your web server can write to it.