VM Within a VM
Yes, it's possible. Greg shows you how.
- By Greg Shields
A training company recently approached me to create some videos on installing
and using VMware's flagship ESX product. They wanted me to demonstrate all of
the product's features and functionality, including ESX's VMotion capability.
That got me thinking about how useful VMotion is to VMware's ESX Server product.
Unless you've had your head in the sand for the last few years, you know that
VMotion is VMware's built-in ability to migrate virtual machines (VMs) from
one host to another without needing to power them down. This "hot migration"
capability is only available in the high-end, high-cost Enterprise Edition of
It's "high-end" because it can migrate machines without losing a
beat. That means much less downtime for critical applications. It's "high-cost"
because you'll need an expensive Enterprise license to run the ESX Server. You'll
also need some form of high-end storage to support VMotion's shared storage
My immediate response to the training company was to tell them about the hefty
hardware I would need to fully demonstrate the software. It just wouldn't be
possible on an author's budget. Then I started digging around and discovered
some new functionality in the recently released desktop version of VMware Workstation
With just a little tweaking, you can get Workstation 6.0 to fully support VMware
ESX instances running inside VMware Workstation. A VM within a VM? Absolutely
-- and depending on your desktop's configuration, it'll pack enough performance
to help you develop your virtualization skills right there at your desktop.
When you're building a VM-within-a-VM environment, you need a powerful desktop
host. After all, that host is running virtual machines that are also running
virtual machines. They'll require lots of RAM and processor power.
You'll need a desktop with at least a dual core that also supports Intel's
Virtualization Technology (VT) processor extensions or newer versions of AMD's
equivalent AMD-V extensions. The virtualization extensions are a necessity because
they help the processor handle the workload associated with virtualization more
efficiently. Your system should also have at least 3GB of RAM to support all
the virtual machines you plan to run.
In order to successfully complete your VMotion setup, you'll need at least
four simultaneously running virtual machines. Two of those will be ESX servers,
the third will serve as the Virtual Center management server, and you will use
the fourth as an iSCSI target for shared storage between the hosts.
ESX Server can use SAN-based storage, NFS and iSCSI targets for its shared
storage where VMotion-capable virtual machines are housed. iSCSI is an excellent
low-cost medium for shared storage as there are numerous open source iSCSI tools
available on the Internet.
OpenFiler, which is an easy to use Linux application, is a good choice. You
can download it from www.openfiler.com.
Once you've installed it within a Linux virtual machine, use OpenFiler's Web
interface to create a disk partition, a volume group and a volume for the shared
storage. Once you're done, you can also use the same interface to share that
volume as an iSCSI target with your ESX servers.
Once you've completed the setup process, you can create a fully functional ESX
virtual machine by following these steps (or find them online here):
• Create a new custom virtual machine. Set its hardware compatibility
to "Workstation 5" and check the box marked "ESX Server Compatible."
• Select the Red Hat Linux operating system, then provide the
machine a name and location.
• Give the virtual machine two virtual processors and around 1024MB
of RAM. The quantity of RAM assigned to the virtual machine will depend on the
RAM available in the host system.
• Select the bridged network option and choose an LSI Logic SCSI
adapter for the virtual machine.
• Create a new virtual SCSI disk. Make sure it's large enough
to host the ESX software and any other hosted virtual machines. It's usually
a good idea to create these disks as pre-allocated to ensure the best performance.
• Once you've created the virtual machine, remove it from the
VMware Workstation interface and the favorites list, and close down that Workstation
instance. This ensures that the system isn't using the virtual machine's files
we need to edit next.
• Open the new virtual machine's .VMX file in a text editor and
make sure the following lines are present for each connected Ethernet adapter.
If there are multiple cards configured for the ESX instance, there will be one
copy of each of these lines for each adapter:
ethernet0.present = "TRUE"
ethernet0.virtualDev = "e1000"
ethernet0.connectionType = "bridged"
ethernet0.addressType = "generated"
You'll need to add the following lines in the .VMX file for Intel-based CPUs:
monitor_control.restrict_backdoor = TRUE
monitor_control.vt32 = TRUE
If the processor is AMD-based, replace the line monitor_control.vt32
= TRUE with monitor_control.enable_svm = TRUE.
Reconnect the virtual machine with the Workstation interface, make sure the
ESX media is in the CD drive and connected into the virtual machine, and boot
the virtual machine.
This will begin the process of installing the ESX operating system into the
virtual machine. Once the installation and subsequent reboot is complete, you
can tell whether the install was successful if the server boots to the typical
ESX screen. Repeat the process for the second ESX server and create the Windows
Server virtual machine for the Virtual Center server.
Once all components are configured, connect the ESX servers to the OpenFiler
iSCSI data store and create your VM within a VM.
Although this configuration won't be fast enough to run any production virtual
machines, it gives you enough performance to learn the product or study for
certification exams without consuming valuable server resources. The VMware
online community was very helpful in bringing this capability into reality.
Greg Shields is Author Evangelist with PluralSight, and is a globally-recognized expert on systems management, virtualization, and cloud technologies. A multiple-year recipient of the Microsoft MVP, VMware vExpert, and Citrix CTP awards, Greg is a contributing editor for Redmond Magazine and Virtualization Review Magazine, and is a frequent speaker at IT conferences worldwide. Reach him on Twitter at @concentratedgreg.