How to Resize Linux LVM Disk on Azure

Expanding disk capacity in a cloud environment is a common task, but when using Logical Volume Manager (LVM), it requires a specific sequence of actions to ensure data integrity. In this guide, we will walk through resizing an Azure Managed Disk and reflecting those changes within the Linux OS.

[Image of Linux LVM architecture showing PV, VG, and LV]

Prerequisites

• Ensure you have the necessary permissions in Microsoft Entra ID to manage Virtual Machine resources.
• Access to the Azure Serial Console.
• A full backup or snapshot of your disk is highly recommended before performing partition changes.

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Phase 1: Azure Portal Operations

Before the OS can see more space, the physical layer must be expanded.

1. Stop and Deallocate: You must stop the VM from the Azure Portal to change disk sizes. Ensure the status is Stopped (Deallocated).
2. Change Disk Size: - Navigate to the Disks blade of your VM.
   • Select the target disk and go to Size + performance.
   • Increase the size and click Save.

Phase 2: Operating System Configuration

After starting the VM, we need to redistribute the new space across the LVM layers.

1. Verification

Connect via Serial Console and switch to the root user:

sudo su -

List your current block devices and LVM status:

lsblk
pvs
lvs

2. Partition Resizing with fdisk

We need to redefine the partition boundaries for /dev/sda.

fdisk /dev/sda

Follow these exact steps within the fdisk prompt:

• p: List partitions.
• d: Delete the partition (usually number 2 for LVM). Note: This does not delete the data.
• n: Create a new partition.
• Enter: Use the default partition number (2).
• Enter: Use the default first sector.
• Enter: Use the default last sector (this picks up the new space).
• n: When asked to remove the signature, type No.
• w: Write changes and exit.

If you accidentally remove the signature, the LVM metadata will be lost. Always select ‘No’ when prompted.

3. Expanding the LVM Layers

Now, we inform the LVM management layer about the partition change.

Resize the Physical Volume (PV):

pvresize /dev/sda2

Resize the Logical Volume (LV): We will use the -r flag to resize the underlying filesystem automatically.

lvresize -r -L 180G /dev/rootvg/homelv

Grow XFS Filesystem: If the filesystem did not expand automatically with the previous command, use:

xfs_growfs /dev/rootvg/homelv

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Summary of Changes

By following this workflow, we successfully achieved the following expansion:

Component	Before Extension	After Extension
Physical Volume (PV)	63 GB	255 GB
Logical Volume (LV)	1 GB	180 GB

Your Linux environment now has the additional capacity ready for use without a reboot.

Always verify the final state using the df -h command to ensure the filesystem reflects the changes.