Expand Virtual Hard Disk: Resizing in Windows Server Core

Windows Server Core has no Disk Management GUI, but expanding a virtual hard disk is straightforward with PowerShell — it’s actually a two-step process, since the VHD/VHDX file itself and the partition inside it are resized separately.

Step 1 — Expand the Virtual Disk (on the Hyper-V Host)

Resize-VHD -Path "D:\VMs\Server01\Server01.vhdx" -SizeBytes 100GB

The VM must be shut down (or the disk not currently in an active checkpoint/snapshot chain) for this to succeed against most disk types.

Step 2 — Expand the Partition (Inside the Guest)

Boot the guest, open a PowerShell session on the Server Core install, and check the partition and its supported maximum size:

Get-Partition -DriveLetter C
Get-PartitionSupportedSize -DriveLetter C

Then resize the partition to fill the newly available space:

Resize-Partition -DriveLetter C -Size (Get-PartitionSupportedSize -DriveLetter C).SizeMax

Run Get-Volume afterward to confirm the drive now reports the expected total size.

If Step 1 Fails: Common Reasons

A few things worth checking if Resize-VHD itself refuses to run before you get anywhere near the partition step: confirm the VM is fully shut down rather than saved/paused (a saved state can behave like the disk is still in use), confirm there isn’t an active checkpoint/snapshot chain on the disk (checkpoints lock the base VHDX against direct resize — you’d need to remove or merge checkpoints first), and confirm the Hyper-V host itself has enough free space on the underlying volume to accommodate the requested growth if the VHDX is dynamically expanding rather than fixed-size. It’s also worth double-checking you’re targeting the correct file if the VM has multiple virtual disks attached — running Get-VMHardDiskDrive -VMName Server01 on the host lists every disk path attached to that VM, which is a safer way to confirm the exact path than guessing from the VM name alone, especially in environments where VHDX files aren’t stored in an obviously-named folder structure. One more distinction worth knowing if you’re working across mixed environments: this Hyper-V-specific two-step process (host-level VHD resize, then guest-level partition resize) doesn’t directly apply to Azure VMs or VMware — Azure disk resizing is done through the Azure portal/CLI against the managed disk resource rather than Resize-VHD, and VMware uses its own vSphere-side disk expansion tools, though the guest-side Resize-Partition step is the same regardless of hypervisor once the underlying disk has actually grown.

Resources

• Server Core
• disk space
• Hyper-V
• VMWare