Resizing a VM’s disk within Azure

Random notes on resizing a disk attached to an Azure VM …


Check what you have already –

az disk list --resource-group MyResourceGroup --query '[*].{Name:name,Gb:diskSizeGb,Tier:accountType}' --output table

might output something a bit like :

Name Gb
———————————————- —-
foo-os 30
bar-os 30
foo-data 512
bar-data 256


So here, we can see the ‘bar-data’ disk is only 256Gb.

Assuming you want to change it to be 512Gb (Azure doesn’t support an arbitary size, you need to choose a supported size…)

az disk update --resource-group MyResourceGroup --name bar-data --size-gb 512

Then wait a bit …

In my case, the VMs are running Debian Buster, and I see this within the ‘dmesg‘ output after the resize has completed (on the server itself).

[31197927.047562] sd 1:0:0:0: [storvsc] Sense Key : Unit Attention [current]
[31197927.053777] sd 1:0:0:0: [storvsc] Add. Sense: Capacity data has changed
[31197927.058993] sd 1:0:0:0: Capacity data has changed

Unfortunately the new size doesn’t show up straight away to the O/S, so I think you either need to reboot the VM or (what I do) –

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

at which point the newer size appears within your ‘lsblk‘ output – and the filesystem can be resized using e.g. resize2fs