yes in the beginning i am confusing, but now i am clear about it, their is also a common thing in the output of the Virtual machine
i don't know why this is same!!!!! in each "vmware" virtual-machine

Get the vendor information
 

cat /sys/class/dmi/id/sys/vendor

From VM you will get

cat /sys/class/dmi/id/sys_vendor
VMware, Inc.

From Dell box you will get
cat /sys/class/dmi/id/sys_vendor
Dell Inc.

Simple & Straight forward :)
 

dmidecode -s system-product-name

Surely the way one tell the difference between VMs and real ones is looking at the records and change paperwork? for an audit of even a badly-run network you ought to know, at lest, which VM[s] to expect .
Apologies for the cynicism but I'm not sure why this needs to be asked?

Some reasons...
 

* Maybe you are asked to report the percentage of VMs in a customer's network you are assessing
* Define which virtualization platform is being used to mitigate related vulnerabilities
* Audit purposes: assure specific network subnet for VMs, ....
* Servers foot printing before an attack you will do!

It could be anything, dealing with various setups leads to unexpected questions. Trust me