The Hyper-V Boot Error: ‘The Image’s Hash and Certificate Are not Allowed’ occurs while trying to install Linux CentOS on a virtual machine running on a Hyper-V server.

Here at Bobcares, we have seen several such Hyper-V-related errors as part of our Server Management Services for web hosts and online service providers.

Today we’ll take a look at the causes for this error and see the fix.

Why the image’s hash and certificate are not allowed

Generally, this error occurs while trying to install Linux CentOS on a virtual machine running on a Hyper-V server.

The main reason for this error to occur is that the Hyper-V by default uses UEFI with Secure Boot mode enabled for its Generation 2 virtual machines.

Secure Boot prevents the boot from an untrusted Linux bootloader in the ISO file. Thus this error occurs. For instance, the error appears as below.

How we resolve the error ‘image’s hash and certificate are not allowed’

Now let’s take a look at the steps our Support Engineers follow to resolve this error.

First, to start the installation, we disable Secure Boot in the virtual machine settings (Settings >> Security >> uncheck the option Enable Secure Boot).

Or else we can leave Secure Boot enabled. But we prefer using Microsoft UEFI Certificate Authority template instead of Microsoft Windows. Because according to Microsoft, this template allows you to run Linux distros in the Secure Boot compatibility mode.

Then we restart the VM and boot it again from the CentOS installation ISO image or another Linux distribution.

In the same way, we manage the Secure Boot and templates setting of VM using PowerShell. We run the below command to get the current VM firmware settings.

Get-VMFirmware -VMName “centos7”

Here is the command we use to disable Secure Boot mode for the VM:

Set-VMFirmware -VMName “centos7” -EnableSecureBoot Off

Finally, in order to change the bootloader certificate validation template to the one compatible with most Linux distros:

Set-VMFirmware -VMName “centos7” -EnableSecureBoot On -SecureBootTemplate “MicrosoftUEFICertificateAuthority”

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Conclusion

In short, this error occurs while trying to install Linux CentOS on a virtual machine running on a Hyper-V server. Today, we saw the solution provided by our Support Engineers.