How to set by script a new unique UUID.bios

Issue

A colleague of mine asked me help with creating a powershell script, to change the UUID.bios value in the .vmx file due to a problem related to VMs restored from backups with the same UUID. The issue is related to the fact that both VMs (source and recovered) with the same UUID.bios are present on the execution environment at the same time.

Solution

Googling around I found an old thread on the VMNT community answered by Luc Dekens.
There are several ways of doing in it, from manual to programmatic (as can be seen in this KB article)

I've chosen to write a PowerCLI script. So, I took the Luc's code (thanks for sharing with the community) and readjusted for my needs as described below.
The steps to follow are:

• shutdown the VM
• get the current UUID
• change the UUID (with one autogenerated)
• power on the VM

The new UUID is generated by a static prefix plus the date in the format Year, Month, Day, Hours, Minutes, Seconds, where first 2 digits are taken for all of them (example Get-Date -UFormat "%y%m%d%H%M%S").

############################################################################################
#
#  File  : Change-UUID.BIOS.ps1
#  Author: Lorenzo Moglie
#  Date  : 12.08.2021
#  Description : This script disconnect can be used for generate a new UUID for the target VM
#
#  Usage: .\Change-UUID.BIOS.ps1 <vm-name>
#
############################################################################################

if ($args[0].length -gt 0) {
 $vmName = $args[0]
} else {
 Write-Host -ForegroundColor red "Usage: .\Change-UUID.BIOS.ps1 <VM Name>"
 exit 40
}


Connect-VIServer -Server <VCENTER> -User <USERNAME> -Password <PASSWORD>

$vm = Get-VM -Name $vmName
#Write-Host OLD.UUID=$($vm.extensiondata.config.uuid)

if ((Get-VM -Name $vmName).PowerState -eq "PoweredOff") {
  Write-Host -foreground Green "- VM"$vmName "is already OFF"
}
else
{
    Write-Host -foreground Red "- VM"$vmName "is shutting down ..." 
    $vm | Shutdown-VMGuest  -Confirm:$false
    While ((Get-VM -Name $vmName).PowerState -ne "PoweredOff") {
        Write-Host -foreground yellow "... waiting for" $vmName "to power off"
    sleep 5
    }
}

$newUuid = "6d6f676c-6965-6c31-2e30-" + $(Get-Date -UFormat "%y%m%d%H%M%S")

$spec = New-Object VMware.Vim.VirtualMachineConfigSpec
$spec.uuid = $newUuid
$vm.Extensiondata.ReconfigVM_Task($spec)

Write-Host -foreground Green "- VM"$vmName "successfully updated."
Write-Host "OLD.UUID="$($vm.extensiondata.config.uuid)
Write-Host "NEW.UUID="$newUuid

Write-Host -foreground Green "- VM"$vmName": Restarting in progress ...."
Start-VM -VM $vm -RunAsync 

Disconnect-VIServer -Server * -Force -Confirm:$false

let's see below how the outcome looks like ...

a double check.

UUID.BIOS changed ... Everything look fine.

That's it.