Resolving Phantom VHDX Attachment in Hyper-V: A Complete Guide

Overview

A common and frustrating issue in Hyper-V is when a virtual machine (VM) gets into a state where a .vhdx file is believed to be attached, but you can't see or remove it using the GUI. This phantom attachment prevents the VM from booting or re-attaching the disk. This guide walks through identifying, resolving, and preventing this issue.

Symptoms

VM fails to start.
Attempting to re-attach a .vhdx file results in: The file is already in use or Access denied.
Disk Manager and Hyper-V Manager show inconsistent states.

Root Cause

Hyper-V maintains state information for disk attachments that may not be visible in the GUI. If a VM crashes or is forcibly shut down while using a .vhdx, the virtual disk file may remain logically attached in the VM configuration—even after reboots.

Step-by-Step Resolution

1. Identify Attached VHDX Files

Get-VMHardDiskDrive -VMName "ubuntu"

2. Forcefully Remove Phantom VHDX

Try the exact location first:

Remove-VMHardDiskDrive -VMName "ubuntu" -ControllerType SCSI -ControllerNumber 0 -ControllerLocation 0

Or search and remove:

Get-VMHardDiskDrive -VMName "ubuntu" | Where-Object { $_.Path -like "*efolder.vhdx" } | Remove-VMHardDiskDrive

3. Re-Attach Cleanly

Add-VMHardDiskDrive -VMName "ubuntu" -ControllerType SCSI -ControllerNumber 0 -ControllerLocation 0 -Path "D:\disks\efolder\efolder.vhdx"

4. Start the VM

Start-VM -Name "ubuntu"

Optional: Check for File Locks

Use SysInternals:

handle.exe "efolder.vhdx"

Or from PowerShell:

Get-Process | Where-Object { ($_ | Get-ProcessHandle -ErrorAction SilentlyContinue) -match "efolder.vhdx" }

Prevention Tips

Avoid force shutdowns of VMs with active disks.
Regularly snapshot/export VM configurations.
Use fixed VHDX disks when stability is critical.

Mermaid Diagram: Resolution Flow

flowchart TD A[VM fails to start] --> B[Check disk attachment status] B --> C{VHDX shown as attached?} C -- Yes --> D[Run Remove-VMHardDiskDrive] C -- No --> E[Run Get-VMHardDiskDrive & search by path] D & E --> F[Run Remove-VMHardDiskDrive on match] F --> G[Re-attach disk cleanly] G --> H[Start VM] H --> I{VM boots?} I -- Yes --> J[Done ✅] I -- No --> K[Check file locks or logs]

Visual flowchart of the resolution process.

Conclusion

Phantom .vhdx attachments are a known but solvable problem in Hyper-V. With PowerShell, you can identify and surgically remove hidden disk associations, restoring full control over your VM configuration.

For deeper issues, you may also consider exporting and re-importing the VM after cleanup.

Need help automating this in a script? Let me know!