treat virtual machines like hardware

Signed-off-by: Nico Schottelius <>
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Nico Schottelius 2014-03-30 19:15:23 +02:00
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[[!meta title="Treat Virtual Machines like Hardware"]]
## Appeal
Treat virtual machines like hardware - this is an appeal to every
virtualisation provider and a report from my sysadmin view on
a sensible way to run small to large infrastructures: Consistent.
Before I go into detail, let me first explain you the situation.
## Once upon a time...
... virtualisation was new and slow. [[!qemu]] was the only
emulator that was kind of usable. Slow, but working. Then,
some time later, the CPU vendors began to add support for virtualisation
in hardware and soon virtual machines were kind of running smoothly.
Xen and VMWare appeared and took their share in the market, while qemu
had its closed source driver, kqemu.
Then light virtualisation began its time with software like
[[!uml]] and OpenVZ. All of sudden somebody propagated the buzzword
cloud and with it the use of virtualisation spread. And with it the
problem I am adressing in this article:
## Virtualisation is treated differently to hardware
With mass building virtual machines, new problems have risen:
How to manage those virtual machines? How to manage the networks?
What about their IP addresses? Where to store, define and assign them?
What are the virtual properties of the VM? How many disks, how much memory and
how many cpu (cores) are utilised?
So to solve these problems tools like
[libvirt]( or [openstack](
are deployed. Problem solved?
## Problem invented: (D)RY
Interestingly, au contraire de common belief, with inventing tools specific to
virtualisation management, new problems were in the sysadmin world have been
created: The domain specific tools can only be used for management of VMs
(sic!) and thus require the sysadmin to learn a new tool with different
characteristics from existing tools to manage hardware (I am excluding the effort to run
and maintain a second tool, because I assume in a automated environment this is negligible).
You may claim that virtual machines are different from hardware, but ...
## ... Virtual machines are made to closely resemble hardare
Indeed, the idea of virtual machines is that
***a virtual machine should behave like its hardware equivalent***.
As such I postulate
Treat virtual machines like real machines
Some of you may now be wondering, ...
## ... How to treat VMs and hardware the same
In my opinion (I believe in the [[!kiss]]), managing large scale infrastructures can be as easy
as managing small infrastructures - given you take the right approach. From a technical
point of view, manage an infrastucture you need
* an inventory management tool (like [[cinv|software/cinv]])
* that is the central tool to record all your hosts
* that defines IP address mapppings (mac<->ip, f.i. [[!dhcp]] and ip<->name, like [[!dns]])
* a configuration management system (like [[cdist|software/cdist]])
* that realises your centrally defined configurations
* that manages all your configurations (including VMs!)
## Summary
VM and hardware can easily be managed the same way.
We at [[!ungleich]] take this approach for every infrastructure of our customers
and so far succeed very well with this approach. We do in fact eat our own dogfood
and manage the inventories of our customers (HW and VM!) with [[cinv|software/cinv]]
and configure their infrastructures with [[cdist|software/cdist]].
To support multiple customers, we keep their configurations in
different branches using [[!git]] (logically, if you follow the
## Future
There is a lot of work going on at ungleich in the area of virtualisation using
cdist and cinv. We plan to publish more [!!cdistexamples]] and documentation about
this soon - so stay tuned if you are interested in seeing the
***world's simplest virtualisation infrastructure [tm]*** soon.
[[!tag ungleich vm unix]]