Changing or keeping a UUID for a moved virtual machine

Products

• VMware Desktop Hypervisor
• VMware vSphere ESXi

Issue/Introduction

You moved virtual machine's files to a new location. When you power on the virtual machine, VMware Workstation displays a message asking whether you want to create a new unique identifier (UUID) for the virtual machine or keep the old one. What should you do?

Environment

VMware vSphere ESXi 6.x
VMware vSphere ESXi 7.x
VMware vSphere ESXi 8.x

Resolution

Each virtual machine is automatically assigned a universally unique identifier (UUID), which is stored in the SMBIOS system information descriptor. It can be accessed by standard SMBIOS scanning software (for example, SiSoftware Sandra or the IBM utility smbios2) and is used for system management in the same way you use the UUID of a physical computer.

The UUID is a 128-bit integer. The 16 bytes of this value are separated by spaces, except for a dash between the eighth and ninth hexadecimal pairs. A sample UUID looks like this:

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

The UUID is based on the physical computer's identifier and the path to the virtual machine's configuration file. This UUID is generated when you power on or reset the virtual machine. As long as you do not move or copy the virtual machine to another location, the UUID remains constant.

If you move or copy the virtual machine, you may be offered the choice of creating a new UUID or keeping the old UUID when you first power on the virtual machine. This new UUID is based on the physical computer's identifier and path to the virtual machine's configuration file in its new location.

When you power on a virtual machine that was moved or copied to a new location, the following message usually appears:

1. The virtual machine's configuration file has changed its location since its last poweron. Do you want to create a new unique identifier (UUID) for the virtual machine or keep the old one?
   • Create
   • Keep
   • Always Create
   • Always Keep
2.  Question (id = 0) : msg.uuid.altered: This virtual machine might have been moved or copied.

In order to configure certain management and networking features, VMware ESXi needs to know if this virtual machine was moved or copied.

If you don't know, answer "I copied it".

• Cancel
• I moved it
• I copied it

If you moved this virtual machine, you can choose to keep the UUID. Select Keep/I moved it, then click OK to continue powering on the virtual machine.

If you copied this virtual machine to a new location, you should create a new UUID since the copy of the virtual machine is using the same UUID as the original virtual machine. Select Create/I copied it, then click OK to continue powering on the virtual machine.

If the original virtual machine is being used as a template for more virtual machines, you can choose to create a new UUID the first time you power on each copy. After you configure the virtual machine and are ready to make it a template, move it to a new location and power it on. When the message appears after you power on, select Always Create, then click OK to continue powering on the virtual machine. The virtual machine is set up to create a new UUID every time it is moved. Power off the virtual machine and begin using it as a template by copying the virtual machine files to other locations.

If you intend to move the virtual machine numerous times and want to keep the same UUID each time the virtual machine moves, select Always Keep and click OK to continue powering on the virtual machine.

Note: If you want to change the Always Keep or Always Create setting, power off the virtual machine and edit its configuration (.vmx) file. Delete the line that contains uuid.action = "create" or uuid.action = "keep". For more information, see Tips for editing a .vmx file (345489).

Sometimes the message quoted above does not appear. The message does not appear in any of the following circumstances:

• The line uuid.bios = "" does not exist in the virtual machine's configuration file.
• The line uuid.bios = "" exists, but has an invalid value.
• The line uuid.bios = "" exists with a valid value, and either the line uuid.action = "keep" or the line uuid.action = "change" exists in the virtual machine's configuration file.

Suspending and resuming a virtual machine does not trigger the process that generates a UUID. Thus, the UUID in use at the time the virtual machine was suspended remains in use when the virtual machine is resumed, even if it has been copied or moved. The next time the virtual machine is rebooted, however, the message appears, so you can choose to create a new UUID or keep the existing one.

Specifying a UUID for a Virtual Machine

Note: VMware Tools may need to be removed from the virtual machine prior changing the UUID to prevent the UUID from reverting.

In some circumstances you may want to assign a specific UUID to the virtual machine. To do this, you need to override the automatically generated UUID value. Power off the virtual machine and edit its configuration (.vmx) file to set the value of the UUID parameter. Use a text editor to edit the configuration file. The format for the line is:

uuid.bios = ""

 

The UUID value must be surrounded by quotation marks. A sample configuration line looks like:

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

 

After you add this line to the configuration file, power on the virtual machine. The new UUID is used when the virtual machine boots.