🧪 Offline Boot Testing & Generalization of VHDX OS Images

🔪 Offline Boot Testing & Generalization of VHDX OS Images

This guide follows the Disk2vhd imaging and Azure upload process. In networks where the .vhdx is synced to local hypervisor storage, the image must be tested offline to validate bootability before being generalized and cleaned.

1. 🔌 Boot Test in Local Staging Hypervisor

Objective:

Ensure the .vhdx image boots in a virtual machine within a completely offline staging environment.

Steps:

Import the .vhdx into your hypervisor (e.g., Hyper-V, Proxmox, VMware Workstation).
Create a test VM:
- Connect the disk as the primary boot volume.
- Ensure no internet/network adapters are connected.
Power on the VM.

🏢 Special Case: Ridgebrook Client Deployment

For Ridgebrook:

Images stored in the Azure file share:
- Storage account: clientosimages01e2usdtc
- File share: client-os-images-01
The image should be synced to the local staging hypervisor:
- Hypervisor name: ELDERBRAIN
- Local path:
  D:\Virtual Hard Disks\client-os-images-01
Ridgebrook .vhdx images should be placed into a subfolder matching their PSA company name (e.g., ridgebrook-industrial).

Once synced, follow the standard boot validation and conversion process below.

2. 🔄 Convert MBR to GPT (If Needed)

If the VM fails to boot, the .vhdx likely uses MBR instead of GPT.

✅ Option 1: MBR2GPT (Recommended)

Steps:

Boot into Windows Recovery Environment or ISO shell.

Run:

mbr2gpt /validate /disk:0 /allowFullOS
mbr2gpt /convert /disk:0 /allowFullOS

Make sure the OS volume is the last volume and delete any non-essential partitions (see below).

3. 🧼📼 Cleaning Up Partitions With DiskPart

Target Partition Layout (Post-Conversion):

Partition	Purpose	Size
1	EFI System	10 GB
2	Recovery	10 GB
3	OS Volume	Remainder

Why fixed sizes?
Microsoft has misaligned these in the past — we standardize to 10 GB for EFI and Recovery to avoid risk.

DiskPart Steps:

diskpart
list disk
select disk 0
list partition

Delete unwanted partitions (OEM, redundant recovery, etc).
Create EFI:

create partition efi size=10240
format quick fs=fat32 label="System"
assign letter=S

Create Recovery (optional):

create partition primary size=10240
format quick fs=ntfs label="Recovery"
assign letter=R

4. 🥾 Rebuild BCD Bootloader

bcdboot C:\Windows /s S: /f UEFI

C: = OS path
S: = EFI partition
/f UEFI = Force GPT boot

5. 🧽📽 Generalize the OS Image (Post-Boot Cleanup)

Once the VHDX boots successfully in offline staging, perform the following steps to prepare it as a reusable image.

👥 Optional: Backup & Remove User Profiles (for shared deployments)

If this image will be deployed to ~~clear~~multiple ~~agent~~VMs ~~registration~~or ~~info~~physical workstations, it's important to remove all local user accounts and ~~then~~profiles ~~run~~to avoid SID duplication and profile conflicts.

Step 1: Backup Profiles with ProfWiz

Use ForensiT User Profile Wizard (ProfWiz) to safely back up and preserve profiles before deletion:

Download and extract ProfWiz (free or corporate version).

Run the wizard for each profile you want to migrate or preserve.

Store exported profiles to a secure backup path or network share.

Step 2: Delete Local User Profiles

After confirming the backups:

wmic useraccount where "name!='Administrator' and name!='DefaultAccount' and name!='Guest' and name!='WDAGUtilityAccount'" delete

Then delete local user profile folders:

for /D %%i in (C:\Users\*) do (
  rd /s /q "%%i"
)

⚠️ Be cautious: This ~~Sysprep~~permanently deletes. all local user accounts and their data, except system accounts.

🔐 Clear Agent Identity & Token Data

Do not uninstall the agents — only remove identity/config/token files to force a fresh enrollment after Sysprep.

Tool	Remove Registration From
NinjaRMM	~~Delete contents of:~~
`C:\ProgramData\NinjaRMMAgent\` ~~(excluding binaries if needed)~~
Blackpoint	~~Delete:~~`C:\ProgramData\Blackpoint\` and token files
Veeam Agent	`C:\ProgramData\Veeam\`
MSP360	`C:\ProgramData\CloudBerryLab\`

C:\ProgramData\Blackpoint\

~~Any~~ .json or .db ~~token/cache files | |~~ ~~Veeam Agent~~ ~~| Clear config from:~~

C:\ProgramData\Veeam\

~~Delete any persistent task or repo references | |~~ ~~MSP360~~ ~~| Remove:~~

C:\ProgramData\CloudBerryLab\

~~Clear backup plans and identity info |~~

🧹🥵 Windows Log Cleanup

del /s /q C:\Windows\System32\winevt\Logs\*.*
del /f /q %SystemRoot%\Panther\*.*

6. 🧾💾 Optional: Skip OOBE with `unattend.xml`

To bypass Out-of-Box Experience (OOBE) and skip all prompts (including user account creation), use an unattend.xml file with Sysprep.

🔒🔐 Note: This method will not create new user accounts, and will not alter existing ones.

Key Capabilities:

Skips first-time setup UI
Does not create or modify user accounts
Disables telemetry and feedback services

Sample `unattend.xml` Snippet

<unattend xmlns="urn:schemas-microsoft-com:unattend">
  <settings pass="oobeSystem">
    <component name="Microsoft-Windows-Shell-Setup" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State">
      <OOBE>
        <HideEULAPage>true</HideEULAPage>
        <HideWirelessSetupInOOBE>true</HideWirelessSetupInOOBE>
        <NetworkLocation>Work</NetworkLocation>
        <ProtectYourPC>3</ProtectYourPC>
        <SkipMachineOOBE>true</SkipMachineOOBE>
        <SkipUserOOBE>true</SkipUserOOBE>
      </OOBE>
      <TimeZone>Eastern Standard Time</TimeZone>
    </component>
  </settings>

  <settings pass="specialize">
    <component name="Microsoft-Windows-Feedback" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State">
      <DisableFeedback>true</DisableFeedback>
    </component>
    <component name="Microsoft-Windows-CEIPEnable" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State">
      <CEIPEnable>false</CEIPEnable>
    </component>
    <component name="Microsoft-Windows-ApplicationExperience" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State">
      <AITEnable>false</AITEnable>
    </component>
    <component name="Microsoft-Windows-ErrorReportingCore" processorArchitecture="amd64" publicKeyToken="31bf3856ad364e35" language="neutral" versionScope="nonSxS" xmlns:wcm="http://schemas.microsoft.com/WMIConfig/2002/State">
      <DisableWerReporting>true</DisableWerReporting>
    </component>
  </settings>
</unattend>

How to Use:

Save as unattend.xml.
Copy to:
```
C:\Windows\System32\Sysprep\
```

Run Sysprep:

sysprep /generalize /oobe /shutdown /unattend:C:\Windows\System32\Sysprep\unattend.xml

✅ Final Checklist

Image booted offline on hypervisor
Converted to GPT, EFI+Recovery+OS partitions validated
Optional: user profiles backed up and deleted (for shared use)

Agent registration/token data cleared
Existing users left untouched unless removed intentionally
unattend.xml disables OOBE and telemetry
Sysprep completed and image shut down cleanly

🧪 Offline Boot Testing & Generalization of VHDX OS Images

🔪 Offline Boot Testing & Generalization of VHDX OS Images

1. 🔌 Boot Test in Local Staging Hypervisor

Objective:

Steps:

🏢 Special Case: Ridgebrook Client Deployment

2. 🔄 Convert MBR to GPT (If Needed)

✅ Option 1: MBR2GPT (Recommended)

Steps:

3. 🧼📼 Cleaning Up Partitions With DiskPart

Target Partition Layout (Post-Conversion):

DiskPart Steps:

4. 🥾 Rebuild BCD Bootloader

5. 🧽📽 Generalize the OS Image (Post-Boot Cleanup)

👥 Optional: Backup & Remove User Profiles (for shared deployments)

Step 1: Backup Profiles with ProfWiz

Step 2: Delete Local User Profiles

🔐 Clear Agent Identity & Token Data

🧹🥵 Windows Log Cleanup

6. 🧾💾 Optional: Skip OOBE with unattend.xml

Key Capabilities:

Sample unattend.xml Snippet

How to Use:

✅ Final Checklist

6. 🧾💾 Optional: Skip OOBE with `unattend.xml`

Sample `unattend.xml` Snippet