Should You Change or Keep the UUID After Moving a Virtual Machine?

Before you read :

Understanding VMware’s “I Moved It / I Copied It” Prompt

If you’ve ever moved a virtual machine’s files to a new datastore or directory — whether in VMware Workstation, ESXi, or vSphere — you’ve almost certainly seen that slightly annoying prompt:

“This virtual machine might have been moved or copied. Do you want to create a new unique identifier (UUID) or keep the existing one?”

Every engineer asks the same question sooner or later:
Does it matter which one I pick?

Yes. And here’s the full explanation — what the UUID is, when it changes, and how to avoid shooting yourself in the foot.

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What Exactly Is a Virtual Machine UUID?

Every VMware virtual machine gets a universally unique identifier — a 128-bit value stored in the VM’s SMBIOS system information descriptor, similar to a hardware UUID on a physical server.

A UUID looks something like:

56 4d ef 2d 3f d4 14 e2-2e 04 c5 34 3a ec ee 65

VMware generates it based on:

The physical host’s identifier
The full path to the VM’s .vmx configuration file

This UUID stays consistent as long as the VM stays in the same place.

Why VMware Asks About “Moved” or “Copied” VMs

When you power on a VM after relocating its files to a new datastore or directory, VMware checks the path and host signature. If they don’t match its previous location, VMware triggers the prompt:

Do you want to create a new UUID or keep the old one?

You’ll typically see one of these prompt versions:

Create / Keep / Always Create / Always Keep
I copied it / I moved it

What you select matters.

When to Choose “Keep” (I moved it)

Choose Keep when:

✔️ You moved the VM — same VM, just a different location
✔️ The VM is still the same logical workload
✔️ You want to maintain:

MAC address consistency
vCenter object relationships
Monitoring and backup mappings
Licensing tied to UUID

This is the safe choice when nothing about the VM is being duplicated — only relocated.

When to Choose “Create” (I copied it)

Choose Create when:

✔️ You copied or cloned the VM
✔️ You want to avoid duplicate UUID collisions
✔️ You’re making a new instance for:

Testing
Deployment
Using templates
Creating multiple identical VMs

Copies must get new UUIDs — otherwise, vCenter, backups, and monitoring can go insane.

Special Case: Using a VM as a Template

If you regularly turn one VM into many new clones:

Move the VM to a new location
Power it on
Select Always Create

This forces VMware to generate a fresh UUID every time the VM is moved, ideal for template workflows.

After that, keep the VM powered off and treat it as your template source.

What If You Want the Same UUID Every Time?

If your workflow constantly moves VMs (e.g., between lab datastores), and you want a stable identity:

➡️ Select Always Keep

VMware will stop asking and reuse the existing UUID indefinitely.

**When the UUID Prompt Does Not Appear**

You won’t see the “moved or copied” prompt if:

uuid.bios is missing from the .vmx
uuid.bios is present but invalid
A forced rule like uuid.action = "keep" or "create" already exists

Also:

Suspending a VM keeps the old UUID
The prompt appears only after a reboot, not after resume

How to Change the UUID Manually

Sometimes you may want to force a particular UUID — for example, to preserve license bindings or recreate consistent lab conditions.

Steps:

Power off the VM
Edit the .vmx file
Add or modify this line:

uuid.bios = "00 11 22 33 44 55 66 77-88 99 aa bb cc dd ee ff"

Reload the VM’s configuration
Power the VM back on

⚠️ Important: Remove VMware Tools before changing the UUID
Otherwise the VM may revert to the previous value.

Removing “Always Keep” or “Always Create” Rules

If you want VMware to ask again in the future:

Power off the VM
Edit the .vmx
Delete the line:

uuid.action = "keep"

uuid.action = "create"

Save and reload the VM.

Quick Decision Table

Scenario	Choice	Why
You moved the VM	Keep / I moved it	Same VM, same identity
You copied the VM	Create / I copied it	Prevents UUID duplication
You use VM as a template	Always Create	Always generate new IDs
You need a stable UUID across moves	Always Keep	Retains identity
You want a specific UUID	Edit `uuid.bios`	Full manual control