Increased disk size appears to have disabled RDP

Hello Steve

Thanks for the detailed description — this is actually a well-known behavior when resizing an OS disk on an Azure Windows VM. The good news is that since you can still reach the VM via Bastion, the VM is likely booting fine, but something went sideways with the RDP stack or the boot configuration during the resize. Here's how I'd approach it:

Step 1: Check Boot Diagnostics first

Before anything else, go to your VM in the Azure Portal → Help → Boot diagnostics → Screenshot. This will tell you whether the VM is stuck at a boot screen, in Safe Mode, or if it's up and running normally at the OS level.

Step 2: Use Azure Serial Console to inspect the boot config

Since Bastion works, try connecting via the Serial Console (Portal → Help → Serial console) and run:

bcdedit /enum

Look for a safeboot flag under the Windows Boot Loader section. If it's present, the VM is booting into Safe Mode — and RDP is simply not available in Safe Mode. You can remove it with:

bcdedit /deletevalue {Default} safeboot

Then restart the VM and try RDP again.

Step 3: Verify the RDP / TermService is healthy (via Bastion)**

While connected through Bastion, open PowerShell as Administrator and run:

Get-Service TermService
netstat -an | findstr 3389

If TermService is stopped or not listening on 3389, you can restart it:

Restart-Service TermService

Also check if the Windows Firewall has RDP (port 3389) unblocked:

Get-NetFirewallRule -DisplayGroup "Remote Desktop"

Step 4: If boot config appears corrupted — use Azure VM Repair

If boot diagnostics shows errors (like 0xc000000f or INACCESSIBLE_BOOT_DEVICE), the disk resize may have affected the BCD store. In that case, the recommended path is to use the Azure VM Repair commands to attach the OS disk to a rescue VM, run CHKDSK and BCD repair, then restore:

az vm repair create --resource-group <RG> --name <VMName> --repair-username azureuser --repair-password 'YourPassword!'
az vm repair restore --resource-group <RG> --name <VMName>

Just to confirm: resizing the Azure disk at the platform level doesn't automatically expand the volume inside Windows. Once RDP is restored, you'll still need to go into Disk Management (or use DiskPart) to extend the C: drive into the new unallocated space.

Thanks,
Manish.

Hi Steve
I wanted to check if my last response made sense. I’d be glad to assist further or explain anything in more detail and please accept as Yes and upvote if the answer is helpful so that it can help others in the community.