When you want to boot a Hyper-V Gen2 virtual machine from an ISO file, it sometimes stubbornly tries to start from another drive, even if the virtual DVD drive is at the top of the boot order. Several reasons could be causing this issue.
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This problem typically arises when you create a new VM and then want to install the operating system from an ISO. In this scenario, if the VM cannot boot from a disk or over the network, it should eventually attempt to access the DVD.

If that doesn't work, you might encounter the following message from Hyper-V's UEFI firmware after a certain timeout:

SCSI DVD The boot loader failed

Even with the ISO file attached the VM cannot boot from the DVD

Even with the ISO file attached the VM cannot boot from the DVD

Change the boot order

To avoid waiting for the PXE boot timeout, it's good practice to move the DVD drive to the first position in the boot order. This is especially important if there's already an OS installed on the disk, and you want to boot from a tools DVD like gparted. You can perform this task in the VM settings under Firmware.

Set the DVD drive to the first position in the boot order

Set the DVD drive to the first position in the boot order

In PowerShell, you can do this with the following commands, assuming the VM's name is ws-2022:

$dvd = Get-VMDvdDrive -VMName ws-2022
$nic = Get-VMNetworkAdapter -VMName ws-2022
$hdd = Get-VMHardDiskDrive -VMName ws-2022
Set-VMFirmware -VMName ws-2022 -BootOrder $dvd, $hdd, $nic

The result of the operation can then be verified as follows:

Get-VMFirmware -VMName ws-2022 | select -ExpandProperty BootOrder

Local path for the ISO file

If the VM still refuses to boot from the DVD, then you should check the path to the ISO file. It cannot be located on a network drive. While VMware Workstation issues warnings if the share is inaccessible, with Hyper-V, you can freely enter a UNC path, which will inevitably lead to boot problems.

For the ISO file you should not enter a UNC path if you intend to boot from the DVD

For the ISO file you should not enter a UNC path if you intend to boot from the DVD

Secure Boot

Once you have ensured that the ISO file is on a local drive, you can eliminate another possible cause by disabling Secure Boot. This feature is located in the Security section.

Secure Boot generally doesn't pose an issue for Microsoft's ISO, including Windows setup, but Linux Live CDs, such as those for various system tools, can be particularly affected. After completing your tasks, you can reenable this feature.

Disable Secure Boot to fix the boot problem

Disable Secure Boot to fix the boot problem

Using PowerShell, you can disable Secure Boot as follows:

Set-VMFirmware -VMName "VM name" -EnableSecureBoot Off

Second SCSI controller

If the previous measures do not resolve the issue, you can try adding an additional virtual SCSI controller to the VM and attaching the ISO to it (IDE controllers are no longer supported in Gen2 VMs).

Sometimes it helps to add a dedicated SCSI controller for the DVD

Sometimes it helps to add a dedicated SCSI controller for the DVD

Check the ISO file

Finally, the problem may lie with the ISO file itself, even if you have created it with the right tools. In this case, try to boot the VM from an original ISO provided by a manufacturer (e.g., the Windows installation media).

Summary

For Generation 2 VMs, there may be occasional issues when booting from an ISO. In such cases, start by moving the DVD up in the boot order and then try various measures.

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These include checking the path to the ISO file, disabling Secure Boot, setting up a dedicated SCSI controller for the DVD drive, and verifying the integrity of the ISO file.

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2 Comments
  1. Avatar
    AJ 1 month ago

    I hit this yesterday except for me it was because a Gen2 VM doesn’t support a 32-bit OS. Yes I had to install a 32-bit OS for some utter tripe software…
    I had to re-make the VM as Gen1.

  2. Avatar
    Predrag 1 month ago

    Hyper-v is sheety because cant boot custom iso images. The end.

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