How do I test a deployment without wiping a machine in MDT?

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Applies to: Microsoft Deployment Toolkit (MDT) 8456 and later
Last updated: May 2025

Problem

You want to test Task Sequences, custom scripts, drivers, or UI configurations in MDT without formatting the hard drive or installing a new OS each time.

Solution

MDT provides several ways to safely test deployments without wiping the target machine. You can disable certain steps, use virtual machines (VMs), or create a special Task Sequence for “Lite Touch” testing.

Option 1: Use a Virtual Machine (Recommended)

Create a test VM with the same configuration as your target hardware:

  • Boot the VM into MDT (via ISO or PXE)
  • Run full or partial deployments
  • Snapshots let you roll back between tests

This is the safest and fastest way to test without affecting physical machines.

Option 2: Disable Disk Formatting in the Task Sequence

Step 1: Open the Task Sequence

  • Deployment Workbench > Task Sequences > Right-click > Properties

Step 2: Disable Format Step

  • Go to the Preinstall phase
  • Right-click Format and Partition Disk > Disable

This allows MDT to run the deployment without erasing existing partitions.

Caution: If the OS installation still proceeds, it may overwrite existing files.

Option 3: Create a “Test Only” Task Sequence

Make a clone of your main Task Sequence and strip out destructive actions:

  • Copy the Task Sequence
  • Remove or disable:
    • Format and Partition Disk
    • Install Operating System
    • Domain Join
  • Keep steps for:
    • Custom scripts
    • Driver injection
    • UI testing
    • Application installs (optional)

This lets you test conditions, logic, and interfaces without impacting the disk.

Option 4: Use Lite Touch Boot Environment Only

Boot into the LiteTouchPE environment and cancel after the wizard loads:

  • This helps test:
    • Wizard customizations
    • CustomSettings.ini rules
    • Application visibility
    • Variable resolution

No changes are made to the machine unless a Task Sequence is started.

Logs and Debugging

Even if the deployment is canceled, MDT generates logs in RAM:

  • X:\MININT\SMSOSD\OSDLOGS\ZTIGather.log (useful for verifying rule logic)
  • Save them manually if needed before shutdown

Notes

  • Testing in a lab or VM first is highly recommended before touching production machines.
  • Keep at least one non-destructive Task Sequence or VM snapshot for quick iteration.
  • You can also simulate deployments using MDT monitoring to observe variables and progress remotely.

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