Need help increaseing the disk size of my VM running linux

Question

Need help increaseing the disk size of my VM running linux

Menno Weijling 0

I need assistance in increasing disk size of the disk attatched to my VM running linux.
Since it's a live production environment, I can't stop the instance. I had had issues before while trying to upgrage disk space.

Himanshu Shekhar 5,225 Reputation points Microsoft External Staff Moderator

2026-03-24T13:53:27.1033333+00:00
You can increase the size of an Azure managed data disk while the Linux VM is running, but issues usually occur inside the OS, not at the Azure platform level.

Azure resizes the disk successfully, but Linux does not automatically expand the partition or filesystem, which causes the disk to still appear full - https://learn.microsoft.com/en-us/azure/virtual-machines/linux/expand-disks?tabs=ubuntu

Most common root causes (why it failed earlier)

Disk resized in Azure, but OS not updated

lsblk shows larger disk

df -h still shows old size

This is expected until the partition/filesystem is extended. [explaintopic.com]

Wrong filesystem command used

resize2fs works only for ext4

xfs_growfs is required for XFS

Using the wrong command causes resize failures. [learn.microsoft.com]

Partition not grown

Disk is larger, but partition still uses old boundaries

growpart must be run first for non‑LVM disks. [learn.microsoft.com]

LVM not extended

If the disk uses LVM, the physical volume and logical volume must be resized

Skipping pvresize / lvextend causes no visible space increase.

1 answer

Your answer

Himanshu Shekhar 5,225 Reputation points Microsoft External Staff Moderator

2026-03-24T13:53:27.1033333+00:00

You can increase the size of an Azure managed data disk while the Linux VM is running, but issues usually occur inside the OS, not at the Azure platform level.

Azure resizes the disk successfully, but Linux does not automatically expand the partition or filesystem, which causes the disk to still appear full - https://learn.microsoft.com/en-us/azure/virtual-machines/linux/expand-disks?tabs=ubuntu

Most common root causes (why it failed earlier)

Disk resized in Azure, but OS not updated

lsblk shows larger disk

df -h still shows old size

This is expected until the partition/filesystem is extended. [explaintopic.com]

Wrong filesystem command used

resize2fs works only for ext4

xfs_growfs is required for XFS

Using the wrong command causes resize failures. [learn.microsoft.com]

Partition not grown

Disk is larger, but partition still uses old boundaries

growpart must be run first for non‑LVM disks. [learn.microsoft.com]

LVM not extended

If the disk uses LVM, the physical volume and logical volume must be resized

Skipping pvresize / lvextend causes no visible space increase.

Answer 1

TP 155.4K Volunteer Moderator

Hi Menno,

Is the disk you want to increase a managed data disk? If it is OS disk you cannot increase the size without first Deallocating the VM. As always make sure you have backup of your VM and all its disks before making changes.

To increase size of managed data disk, navigate to the VM in portal -- on left click Settings -- Disks, click on data disk you would like to increase. Next, on the Disk screen click Settings -- Size + performance. Select the new size and click Save. Wait for notification that says it successfully updated disk.

Now that you have increased the size of the disk, you need to expand the partition and filesystem within the VM. Please see article below for instructions on identifying disk within the operating system and then expanding partition and filesystem.

Expand virtual hard disks on a Linux VM

https://learn.microsoft.com/en-us/azure/virtual-machines/linux/expand-disks

Please click Accept Answer and upvote if the above was helpful.

Thanks.

-TP

Menno Weijling 0 Reputation points

2026-03-25T10:48:50.2666667+00:00

Hi TP,
I am not sure, if it's a managed disk or not .
I needed guided support. Is there any way to have a support for this ?
Himanshu Shekhar 5,225 Reputation points Microsoft External Staff Moderator

2026-03-25T15:48:25.8866667+00:00
Menno Weijling

In the Azure portal:

Go to Virtual Machine > Disks

Select the disk in question

If it shows “Managed disk” (which is the default for all modern Azure VMs), then it can be resized while the VM is running (for data disks)

You can check this as well -

lsblk

df -Th

Note - If the disk turns out to be the OS disk, resizing it requires VM deallocation.

If it is a data disk, it can be expanded without downtime.

Expand virtual hard disks on a Linux VM - https://learn.microsoft.com/en-us/azure/virtual-machines/linux/expand-disks?tabs=ubuntu
Menno Weijling 0 Reputation points

2026-03-25T21:13:30.1+00:00

Is there any option for guided support ?
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Himanshu Shekhar 5,225 Reputation points Microsoft External Staff Moderator

2026-03-26T12:50:57.36+00:00
Based on the screenshots you shared, your VM is using Azure Managed Disks (this is the default for all modern Azure VMs). From the OS output, /dev/sda is your OS disk, mounted as /, and it’s currently 97% full.

Important clarification

Data disks can be resized online (no VM stop)

OS disk (/) requires VM deallocation to resize safely

This is an Azure platform requirement and cannot be bypassed [Expand Vir...soft Learn | Learn.Microsoft.com]

Since your production workload is on the OS disk, that’s why previous attempts likely failed or appeared incomplete. - https://learn.microsoft.com/en-us/azure/virtual-machines/linux/expand-disks?tabs=ubuntu

Note - Your VM uses a managed OS disk, which cannot be resized online; for zero downtime, add a data disk, or plan a short maintenance window to expand the OS disk safely.
Menno Weijling 0 Reputation points

2026-03-27T10:30:29.8066667+00:00

So , if I add an additional disk , and put all my data(code) there, it will run fine without restart and 0 downtime. And will have no performance difference then os disk ?

If yes can you please guide me through the steps please?
Himanshu Shekhar 5,225 Reputation points Microsoft External Staff Moderator

2026-03-30T09:08:09.4933333+00:00
Menno Weijling - Yes. To avoid downtime, add a new managed data disk and move your application/code there.

Data disks can be attached and mounted online (no VM restart).

OS disk ( / ) cannot be resized online — requires VM deallocation.

No performance impact if you choose the same or higher disk SKU (often better than OS disk).

What to do - Azure Portal > VM > Disks > Add data disk (choose size & SKU) > Save

Inside Linux: detect disk (lsblk), partition, format, mount (e.g., /data)

Move app/code to /data and update app paths (or use a symlink)

Add entry to /etc/fstab so it persists after reboot

Microosft Docs

Expand disks on Linux VM: https://learn.microsoft.com/azure/virtual-machines/linux/expand-disks

Add a data disk: https://learn.microsoft.com/azure/virtual-machines/linux/add-disk

This is the recommended production approach for zero downtime.

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Need help increaseing the disk size of my VM running linux

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