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 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. So a sample UUID looks like this:

00 11 22 33 44 55 66 77-88 99 aa bb cc dd ee ff

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 have the choice of creating a new UUID the first time you 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, a message appears.

If you moved this virtual machine, you can choose to keep the UUID. Select Keep, 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, 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, then select Always Keep and click OK to continue powering on the virtual machine.

uuid.action = "create"

or

uuid.action = "keep"

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. However, the next time the virtual machine is rebooted, the message appears, so you can choose to create a new UUID or keep the existing one.

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 file (.vmx) 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 = <uuidvalue>

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