How to attach a Data Disk to a Linux VM in Azure?

1- Go to the Azure portal to find the VM. Search and select Virtual machines.

Choose the VM from the list.

In the Virtual machines page, under Settings, choose Disks.

2- On the Disks pane, under Data disks, select Create and attach a new disk.

Enter a name for your managed disk. Review the default settings, and update the Storage type, Size (GiB), Encryption and Host caching as necessary.

When you are done, select Save at the top of the page to create the managed disk and update the VM configuration.

Connect to the Linux VM to mount the new disk

ssh azureuser@ServerIP

If you are using an existing disk that contains data, skip to mounting the disk. If you are attaching a new disk, you need to partition the disk.

sudo parted /dev/sdc --script mklabel gpt mkpart xfspart xfs 0% 100%
sudo mkfs.xfs /dev/sdc1
sudo partprobe /dev/sdc1

Mount the disk:

Create a directory to mount the file system using mkdir. The following example creates a directory at /datadrive:

sudo mkdir /datadrive

Use mount to then mount the files ystem. The following example mounts the /dev/sdc1 partition to the /datadrive mount point:

sudo mount /dev/sdc1 /datadrive

To ensure that the drive is remounted automatically after a reboot, it must be added to the /etc/fstab file. It is also highly recommended that the UUID (Universally Unique Identifier) is used in /etc/fstab to refer to the drive rather than just the device name (such as, /dev/sdc1). If the OS detects a disk error during boot, using the UUID avoids the incorrect disk being mounted to a given location. Remaining data disks would then be assigned those same device IDs. To find the UUID of the new drive, use the blkid utility:

sudo blkid

Output:

/dev/sda1: LABEL="cloudimg-rootfs" UUID="11111111-1b1b-1c1c-1d1d-1e1e1e1e1e1e" TYPE="ext4" PARTUUID="1a1b1c1d-11aa-1234-1a1a1a1a1a1a"
/dev/sda15: LABEL="UEFI" UUID="BCD7-96A6" TYPE="vfat" PARTUUID="1e1g1cg1h-11aa-1234-1u1u1a1a1u1u"
/dev/sdb1: UUID="22222222-2b2b-2c2c-2d2d-2e2e2e2e2e2e" TYPE="ext4" TYPE="ext4" PARTUUID="1a2b3c4d-01"
/dev/sda14: PARTUUID="2e2g2cg2h-11aa-1234-1u1u1a1a1u1u"
/dev/sdc1: UUID="33333333-3b3b-3c3c-3d3d-3e3e3e3e3e3e" TYPE="xfs" PARTLABEL="xfspart" PARTUUID="c1c2c3c4-1234-cdef-asdf3456ghjk"

sudo nano /etc/fstab

Output:

UUID=33333333-3b3b-3c3c-3d3d-3e3e3e3e3e3e   /datadrive   xfs   defaults,nofail   1   2

To know more in details, checkout below article:

https://docs.microsoft.com/en-us/azure/virtual-machines/linux/attach-disk-portal