Can I run VMs with the same uuid ?

[kelwang]

Hi, I am wondering if it's possible to run multiple VMs with the exact same uuid ? Would that work?

[DavoudTeimouri]

Hi,

Read this blog: http://www.virtuallyghetto.com/2014/07/what-happens-when-virtual-machines-have-duplicate-instanceuui...

I hope, you find your answer.

[vNEX]

Hi,

you cannot run two VMs with completely identical IDs... this topic is quite complex there are several IDs which helps to uniquely identify VMs in VI.

- uuid.bios

- InstanceUuid

- MoRef ID

If system detects duplicity it will always ask you question if the VM was Copied, Moved or if you want to Cancel Power on operation.

According to your answer the host will take appropriate actions for more details see:

VMware KB: Changing or keeping a UUID for a moved virtual machine

For more info about this topic see:

Uniquely Identifying Virtual Machines in vSphere and vCloud Part 1: Overview | VMware vSphere Blog -...

VMware KB: Powering on a virtual machine pauses at 95% while waiting for a question to be answered

VMware KB: Changing or keeping a UUID for a moved virtual machine

How many specific IDs each VM has??

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Regards,

P.

[Cyberfed27]

I know for a fact you can run them with the same - uuid.bios

I know this because our Trend Micro Deep Security Manager was burping this exact alert on a few VM's another admin cloned and didn't clean up properly.

I had to power off the VM and delete that line in the VMX file of the VM. When you power it back on it generates a new randing UUID. Interestingly enough VMware itself didn't seem to care or alert in any fashion. I cannot speak to the other portions being the same as the poster above mentioned. I am merely speaking about the bios ID.

[vNEX]

Yes but if I understand it correctly ... VM UUID is constructed from two values on which the VM uniqueness stands...

- physical host/machine UUID

- actual path to the VM config file/datastore

Then UUID is kept in SMBIOS of the VM (.nvram file) and works in the same way as on the physical machine so on this unique ID depends many SW that needs to identify computer for licensing, management and security purposes...this is the main identifier for all of them. Its also used to generate unique MAC address for the VM.

So no surprise that Trend Micro trigger any changes or duplicity of this value.

Two values mentioned above are also stored in VM config file (.vmx) in this format:

uuid.bios - physical host/machine UUID

uuid.location - actual path to VM config file/datastore

When VM starts SMBIOS location hash is compared to corresponding uuid.location hash in the vmx file and if differs system will ask you  "Moved/Copied".

If you chose moved only uuid.location is changed

If you chose copied both values (bios/location>UUID) are changed including virtual machine MAC address

So this is probably why individual change of uuid.bios value doesn't trigger any system alert ?!

Other unique IDs like instanceUuid and MoReF ID has nothing to do with above purposes of UUID they exist specially for management purposes of virtualization layer such as vSphere API and vCenter server instances.

But all of this is only my personal construct based on the public resources and VMware documentation...so its possible that I am wrong ... in such case any comments from others are greatly welcome.

Regards,

P.