How to Extend a Disk on Azure Linux VM

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You resized a managed disk in the Azure portal but the Linux VM still shows the old filesystem size. This is normal behaviour. Azure expanding the managed disk only grows the raw block device. You still need to extend the partition and then the filesystem inside the VM to extend the disk on your Azure Linux instance. This guide covers all three steps for Ubuntu, Debian, and RHEL-based VMs with no restart needed.

extend disk Azure Linux VM managed disk resize storage
Azure managed disks support live resize on most VM sizes. Partition and filesystem extension still happen inside the OS after the Azure resize.

Step 1: Resize the Managed Disk in Azure

In the Azure portal, go to your VM then Disks, click the disk you want to extend, choose Size + performance, select a larger disk tier, and save. With the Azure CLI:

az disk update --resource-group myRG --name myDisk --size-gb 256

For OS disks on most modern Azure VM sizes, the resize happens without stopping the instance. For older VM sizes, you may need to stop and deallocate the VM first. The full process is on the Azure expand OS disk documentation. Data disks support live resize on all modern VM sizes.

Step 2: Verify the New Disk Size Inside the VM

Azure Linux disk extend az cli terminal commands partition
After Azure resizes the managed disk, lsblk confirms the new block device size before you extend the partition.

SSH into the VM and check that the kernel sees the new disk size:

lsblk

The disk (usually /dev/sda on Azure Linux VMs) should show the new size. The partition below it still shows the old size. If the disk still shows the old value, rescan the SCSI bus:

echo 1 > /sys/class/block/sda/device/rescan

Also note current filesystem usage before making any changes:

df -h

Extend Disk on Azure Linux: Grow the Partition

Install growpart if needed:

# Ubuntu / Debian
apt install cloud-guest-utils -y

# RHEL / AlmaLinux / Rocky Linux
dnf install cloud-utils-growpart -y

Extend the partition to use all available space:

growpart /dev/sda 1
lsblk

The partition should now match the full disk size. If your Azure VM uses LVM on the root volume (common with RHEL images from the Azure Marketplace), also resize the LVM layers:

pvresize /dev/sda1
lvextend -l +100%FREE /dev/rootvg/rootlv

See our LVM disk management guide for full details on LVM resize operations.

Step 3: Extend the Filesystem

extend disk Azure Linux VM filesystem growpart resize2fs
Growing the filesystem is the final step. On most Azure Linux VMs, this needs no downtime or restart.

Grow the filesystem to use the new partition space:

# Check filesystem type
df -Th

# ext4 - Ubuntu and Debian Azure images
resize2fs /dev/sda1

# XFS - RHEL, AlmaLinux, Rocky Linux Azure images
xfs_growfs /

# Confirm
df -h /

Azure VMs have a temporary disk at /dev/sdb used for swap or temp storage. Make sure you identify your OS disk correctly with lsblk before running any partition commands. You can also use ls -l /dev/disk/azure/ which Azure populates with named symlinks to help match block devices to managed disks.

Resize Azure Data Disks

The same three-step process applies to data disks. First resize with the az disk update command, then grow the partition with growpart, and finally resize the filesystem at the data mount point. No unmounting is required.

Conclusion

To extend a disk on Azure Linux, resize the managed disk in Azure, extend the partition with growpart, and grow the filesystem. Most Azure VM sizes support this without any restart. The whole process takes under ten minutes. For the AWS equivalent, see our guide on extending disk size on AWS EC2 Linux since the partition and filesystem steps are nearly identical across cloud providers.

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