Another day, another interesting situation in the VMware world.
Straight to the issue: the cloned virtual machines’ VMDK file(s) will point to the VMDK file(s) of the source machine used for the clone.
In other words, when cloning a virtual machine, if you select the checkbox to “customize this virtual machine’s hardware” and change any of the settings of the VM, the cloned virtual machine’s VMDK file(s) will point to the VMDK file(s) of the source machine you used for the clone.
I know that in some cases, you may want to uncheck the network card for the cloned machine, but doing so will cause this issue.
According to VMware KB323391, the workaround is to power off the VM before cloning. However, if you must clone while the VM is running:
Workaround: Simply edit the virtual machine’s hardware after cloning it.
If you must check the box and customize the virtual machine hardware before cloning for some reason, you can still edit the cloned VM’s settings (after it has been cloned) to remove the source VMDK—without checking the “Delete file from datastore” box, as this would permanently delete the files—and then add the existing cloned VMDKs that were created separately.
Another great post on the same issue, written by Matt Allford, is worth checking out.