
The Peculiarly Quiet Decline and Fall of the KVM - blfr
http://www.loper-os.org/?p=1927
======
sdfjkl
KVM switches used to be a huge and super important (and expensive) thing in
rack server farms back when every rack or every few racks had a pull-out tray
with a keyboard and a monitor. Technology moved on. First the tray and monitor
disappeared with KVM-over-IP, which saved many trips to the server room. Then
the KVM switches themselves disappeared, as manufacturers integrated out-of-
band remote access into the servers, first with add-on boards, then onboard
and finally on-chip (this is what Intel AMT does, when it isn't busy running
rootkits).

The little two-PC switch box the article refers to (I think) was always a
spillover from the server KVM technology, except with a very small market and
more difficult to make. Servers don't need sound and are fine with just VGA
video. Home computers want USB (which variety?) and audio switched, or high
bandwidth signals that are very touchy about interference or suddenly being
connected to a different device like HDMI, Displayport or Thunderbolt. And
then people want the stuff for cheap.

> signal switches with arbitrary bandwidth remain available: analogue relays

Have you tried that? Cut a HDMI cable in half and splay it out, then try
switching that to another display. See what happens. If it were that easy,
it'd be around (or you'd just be building it yourself).

~~~
Jaruzel
> Cut a HDMI cable in half and splay it out, then try switching that to
> another display. See what happens.

If you took an ancient (but still available to buy) 25-pin 'parallel port'
4-port switch box with a rotary dial:

[https://photography-909a.kxcdn.com/product-
images/03292/600/...](https://photography-909a.kxcdn.com/product-
images/03292/600/03292a.jpg)

And wired up the HDMI of two machines to output ports 1 & 3[1]. Then wired up
the HDMI to the display to the input port (so effectively using the switch
'backwards'). As you are just simulating unplugging and re-plugging in the
HDMI cable from each machine, via the switch, then surely this would work?

There would be a bit of delay after switching as the HDMI/HDCP handshake
completes, but unless you are switching every few minutes it should be usable?

If it does work, then you've got 6 pins in the switch left to play with which
could be used to switch usb devices (via a downstream hub)

I've not done this, but have thought about it for a while now.

\----

[1] Not ports 1 & 2 as you want to ensure total electrical isolation between
the devices during switching.

~~~
gm-conspiracy
I think the real isssue is with HDCP.

The output device "ensures" the display device is authorized via a key to
output.

So, you would need an intermediary device that would accept any incoming
signal, while also having a legit handshake with the output device.

So, as you switch "inputs", there is no additional authorization required,
because the output device does not detect any changes.

~~~
aidenn0
It's absolutely not HDCP since a 4k HDMI splitter is much cheaper than a 4k
KVM.

My guess is that with KVMs disappearing from server racks, there isn't enough
volume to get the prices we used to get.

------
Kurtz79
PSA:

It's about this "KVM":

[https://en.wikipedia.org/wiki/KVM_switch](https://en.wikipedia.org/wiki/KVM_switch)

Not this:

[https://en.wikipedia.org/wiki/Kernel-
based_Virtual_Machine](https://en.wikipedia.org/wiki/Kernel-
based_Virtual_Machine)

~~~
plq
... which makes this a total non-story in my opinion :)

Of course KVM switches will eventually disappear; when was the last time any
of us (minus datacenter staff) has been to the server room since the dawn of
the PaaS age?

~~~
ztjio
I've only used KVM switches on the desktop. Try to think outside your own
experiences.

------
daemin
The main thing that has pissed me off with technologies like DisplayPort and
HDMI is that I cannot actually turn my monitors off when I'm not using my
computer. With DVI I could turn the monitors off and the desktop and
applications would stay where they were. With HDMI/Displayport it considers
the monitor disconnected, hence re-adjusts the desktop and moves everything
around.

I would love an option that I could switch on and it would "disable HDCP" on
these monitors so they could function like they did before. Sure I couldn't
play some videos but that's not a great loss for me.

~~~
exikyut
There are two possibilities:

1\. Fake GPU software, which I haven't researched at all but probably exists

2\. Forcing your graphics chipset to turn a specific head on and leave it on

Here's a Linux-specific example of how to do #2. Since I'm just talking to
graphics hardware here, there _should_ be equivalent operations for all of the
following for other operating systems.

I don't connect an external display at any point.

First of all, how things look to begin with:

    
    
      $ xrandr   
      Screen 0: minimum 320 x 200, current 1024 x 768, maximum 4096 x 4096
      VGA-0 disconnected (normal left inverted right x axis y axis)
      DVI-0 disconnected (normal left inverted right x axis y axis)
      LVDS connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
         1024x768      60.00*+
         800x600       59.86  
         848x480       59.66  
         720x480       59.71  
         640x480       59.38  
    

Now, `xrandr --output VGA-0 --auto` isn't going to do anything because --auto
will tell the GPU to pick the best resolution. No screen is attached so
there's no list of resolutions to pick from.

So, I'll generate a generic CVT modeline that sets up the VGA output for
1024x768@60Hz.

    
    
      $ cvt 1024 768 60
      # 1024x768 59.92 Hz (CVT 0.79M3) hsync: 47.82 kHz; pclk: 63.50 MHz
      Modeline "1024x768_60.00"   63.50  1024 1072 1176 1328  768 771 775 798 -hsync +
    

Cool. Now I'll tell X11 about the modeline (note the copy-paste):

    
    
      $ xrandr --newmode  "1024x768_60.00"   63.50  1024 1072 1176 1328  768 771 775 798 -hsync +
    

...And now do the XRandR dance to actually tell the _output_ about the right
modeline (this is Xorg-bureaucracy-specific):

    
    
      $ xrandr --addmode VGA-0 "1024x768_60.00"
    

Let's review the xrandr output:

    
    
      $ xrandr
      Screen 0: minimum 320 x 200, current 1024 x 768, maximum 4096 x 4096
      VGA-0 disconnected (normal left inverted right x axis y axis)
         1024x768_60.00  59.92  
      (...)
    

At this point I can go ahead and

    
    
      $ xrandr --output VGA-0 --mode "1024x768_60.00"
    

and my screen displays garbage for a fraction of a second and then figures
itself out.

At this point I know the output is enabled (and the glitch didn't mean
nothing) and in mirroring mode. I can prove this without a display attached by
running xrandr again:

    
    
      $ xrandr
      Screen 0: minimum 320 x 200, current 1024 x 768, maximum 4096 x 4096
      VGA-0 disconnected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
         1024x768_60.00  59.92* 
      (...)
    

Two things: one, the mode has an asterisk next to it, meaning it's active
(albeit without a screen attached), and two (the following will make sense in
a minute if it doesn't straight away) Screen 0 has a "current" size of
1024x768. (Xorg "screens" represent a collection of video outputs you can move
windows between.)

So, let's disable mirroring mode and make this new Schrödinger-pseudo-existent
area its own independent surface.

    
    
      $ xrandr --output VGA-0 --left-of LVDS
    

At this point, i3 (my windowmanager) decides to move every single window onto
the new offscreen surface area, and I go blind. Isn't minimalist software
wonderful? (A new windowmanager is on my todo list; i3 drives me nuts.
Anyway.)

Once I sort i3 out and get back to a terminal, xrandr shows something new and
interesting:

    
    
      $ xrandr
      Screen 0: minimum 320 x 200, current 2048 x 768, maximum 4096 x 4096
      (...)
    

Oh hey, the Screen size is now 2048x768! Proof that I have two 1024x...
outputs configured side-by-side. If I wanted to I could do --above or --below
and have a 1024x1536 display.

Here's the technical moral of the story: since approximately the time of the
dinosaurs monitors have used EDID to provide autodetection info to graphics
chipsets, so forcing manual configuration is pretty deeply buried.

But that's what you need to do; "my screen is weird and needs a custom
configuration" and "okay just set these parameters _and leave the output head
running_ " are analogous.

If you want to turn your screen off and have the GPU keep the head running, I
recommend figuring out how to fish out the modeline your GPU is currently
using, and then force the GPU to manually use that modeline. That should
disable output autodetection and keep the output permanently active.

Despite the fact that I've demoed Linux output configuration here, you're
(ironically) not too likely to have this problem on Linux as Xorg is fairly
flexible, and wouldn't normally need these kinds of instructions provided to
it under normal circumstances; for Linux it would be more "what's explicitly
killing the output and how do I turn it off" as opposed to digging around in
driver settings.

Also - I picked VGA for this example, honestly probably for nostalgic reasons.
These instructions will work equivalently regardless of output type.

~~~
uniformlyrandom
This comment deserves a github gist, and a separate top-level post.

------
hudibras
When I worked in the Pentagon, everybody in our office had these to switch
between the classified and unclassified computer systems. It was amusing when
someone in our large cubicle farm would say, "Hey, check out this email that
just came in on the low side," and then two dozen index fingers would reach
out and two dozen monitors would blink over to the Windows login screen
simultaneously.

~~~
erikbye
G-man here (not the U.S.). Switching between four systems daily. Scroll Lock
x2 + n.

------
oeuviz
Ironically, to me personally KVM [1] is reason #1 for not owning and using the
other KVM [2]. I simply do not need an additional physical machine as what I
need is available in a VM at no cost with plenty of performance.

[1] [https://en.wikipedia.org/wiki/Kernel-
based_Virtual_Machine](https://en.wikipedia.org/wiki/Kernel-
based_Virtual_Machine)

[2]
[https://en.wikipedia.org/wiki/KVM_switch](https://en.wikipedia.org/wiki/KVM_switch)

------
xg15
I'd guess the comment about HDCP is onto something. To build a KVM switch that
works with modern displays without weird errors, it probably has to be an
active HDMI/HDCP endpoint on its own - which means a vendor would either need
to get its own sets of keys and do additional work to enforce all DRM
restrictions - or they'd have to use leaked keys and prepare to get sued in an
instant.

Even without HDCP, I remember another article explaining that it's already
difficult enough to get two arbitrary HDMI devices to talk to each other
because HDMI allows so many different modes of operation. I imagine the
situation would get even worse if you had to negotiate common protocols for
_three_ endpoints at the same time.

~~~
beojan
What if it _physically_ unplugged the HDMI connection, and reconnected it to
the other device? It wouldn't be quite as seamless since the initialization
process would be repeated, but it would _work_.

~~~
blauditore
Not even physically, but just redirecting the raw signal to another device
should work. Maybe artificially break it for a second or so to better simulate
plugging out and back in. I can't see how the actual endpoints could tell a
difference between that and manually un- and re-plugging into a different
device.

~~~
beojan
That's what I meant. Electrically, it's identically to unplugging from one
device and plugging into the other.

------
X-Istence
My monitor has a KVM built in...

[http://www.dell.com/en-us/work/shop/dell-34-ultrasharp-
curve...](http://www.dell.com/en-us/work/shop/dell-34-ultrasharp-curved-
monitor-u3417w/apd/210-adtr/monitors-monitor-accessories)

It has two USB ports that can go to two different computers, and then in the
settings you can set it up so that when you switch from one input to another
it also switches what the USB devices are connected to. There are 4 USB ports
total on the monitor, and they switch from one device to the other.

It's great, instead of being a separate box, it's built into the monitor. It's
neater.

~~~
merb
well this monitor also can daisy chain another monitor. which is awesome per
se, and actually the daisy chained monitor gets switched aswell.
([http://en.community.dell.com/support-
forums/peripherals/f/35...](http://en.community.dell.com/support-
forums/peripherals/f/3529/t/19996478))

but 800 bucks for a monitor :/ I've always looked at these dell monitors. but
I never use a external monitor when I'm at home (laptop). But at work my boss
would never pay for any of those.

~~~
X-Istence
I work from home. I bought it for myself because I like having the extra real
estate. Best purchase I have made in a long time.

Also, I couldn't imagine two of these next to each other, 34" is very large!

------
kindfellow92
Synergy ([https://symless.com/synergy](https://symless.com/synergy)) may have
had something to do with it.

~~~
jsight
Yep, that is what I use for the same usecase. There is really very little
point to a hardware KVM at this point.

~~~
mark-r
The remaining use case is when you want to share a _monitor_ along with the
keyboard and mouse.

------
AdmiralAsshat
These days, I believe the monitor is becoming the KVM. High-end Dell laptops
have multiple inputs as well as USB slots for peripherals, and even a handful
of USB type B to send back downstream.

Mine doesn't, unfortunately, so for my two computers plugged into my Dell
monitor, I have the keyboard and mouse plugged into a cheap USB switch, while
simply cycling through the inputs on the monitor.

It's two clicks instead of one with a traditional KVM, but I don't have $150
to blow on a KVM that has something better than a VGA slot...

------
cesarb
With VGA, it was simple: duplicate the EDID to both inputs, switch the output
wires, done. AFAIK, with DisplayPort it's not so simple, since there is a
negotiation between the computer and the display, including link training (see
[https://lwn.net/Articles/736011/](https://lwn.net/Articles/736011/) for
instance). IIRC, HDMI also has some bidirectional communication. To work well,
a KVM would have to act as a display to the computers, and as a computer to
the display, instead of just passively switching some wires.

------
cr0sh
I read this "article", and a few comments below it - and the replies, and I am
just wondering:

Who is this "Stanislav", and why are they being so grating on people replying?

I mean, I can understand disagreement and correction (ie, the whole "please
re-read the article, your question was answered" or "the article already
addresses this", etc) - but do they have be such an arrogant a __about it?

It basically turned me off from reading further - or exploring the rest of the
blog.

------
blibble
I use two machines as part of normal operation, my monitors have multiple
inputs which can be switched with one button

and with synergy the mouse/keyboard can move across

no need for a KVM

~~~
chha
This! I was a big user of KVMs for many years, but haven't used one for the
past ten(ish) years after discovering Synergy. I don't switch monitor inputs,
but have had a bunch of them connected to various computers, and being able to
switch with no effort at all is great.

------
anoother
Wendell, from the YouTube channel Level1techs, has worked with a Chinese(?)
OEM on custom firmware for Displayport KVMs and is selling them:

[https://twitter.com/tekwendell/status/933441036138971137?s=1...](https://twitter.com/tekwendell/status/933441036138971137?s=17)

Still more expensive than a 4k monitor, but heading in the right direction.

------
Animats
One of the big remaining users of display switching is the military. When
something important is happening on one screen, others need to look at that
screen. The military wants switching so they don't get everybody jammed around
the screen with the action and abandoning their own stations. Here's the
current incarnation of NORAD HQ in Cheyenne Mountain.[1]

Such switching goes all the way back to NASA during Apollo. Their system put
all the screens on a video cable as cable TV signals. Each console, and other
locations around Mission Control and Launch Control, all had channel selectors
and could watch any display. Using different technology, that capability was
maintained in later control centers.

[1]
[https://en.wikipedia.org/wiki/Tactical_operations_center#/me...](https://en.wikipedia.org/wiki/Tactical_operations_center#/media/File:Norad-
control-center.jpg)

~~~
mark-r
If the military needs to spend $1000 on a KVM switch, they won't bat an eye.
That's not true for most of the rest of us.

~~~
revelation
I've seen such kind of "control rooms" where everything was running on VMs
anyway and the individual computers were just remote desktops. It's like they
say, when it gets too difficult, just add a layer of abstraction. They just
went up to software.

------
bitL
I replaced them with standalone USB & HDMI switches. I connect 5 PCs on my
desk (main PC, Deep Learning rig, NAS, 2x NUC) first to two 4-port USB
switches, then have one 2-port switch that switches between these two 4-port
switches, and then a large HDMI switch. It works fine; each of those switches
was <$5.

------
otterpro
What I miss about KVM switch is the ability to switch to another system using
a keyboard hotkey, such as double-pressing the "Scroll Lock" key on the
keyboard. Most high-end KVM had this feature, so that I could use a hotkey to
quickly switch to different system. Once anyone gets used to this, there's no
going back to rotary dials or slow physical push buttons, etc. I had 3 or 4
systems connected to KVM and nothing was faster.

I've tried using modern HDMI/monitor switchbox/splitter and USB switches, but
they require awkward physical reaching for the buttons, as I have to reach out
for a button or two, every time I need to switch to another system. The old
KVM did this in split second and I didn't even have to think about it, sort of
like Vim once you get used to the keys. I was able to work so much faster,
switching from one system to another, whenever I needed to. Now, I have to
think about it before switching, not that I'm lazy, but I don't want to exert
so much energy just to switch to another system.

Edit: I also miss PS/2 and VGA, for their ability to switch quickly as well.
USB devices and HDMI monitors take awhile to switch.

------
AdrianRossouw
I use this one for my 40" 4k monitor, and it works great :
[https://www.amazon.com/gp/product/B01BSNSOPU/](https://www.amazon.com/gp/product/B01BSNSOPU/)

~~~
topspin
That's the second endorsement of an IOGEAR DisplayPort solution I've seen so
far. The full product line is here:
[https://www.iogear.com/solutions/kvm](https://www.iogear.com/solutions/kvm)

$480 to solve the dual head 4K DisplayPort problem, and it works, apparently.

Now, is that a reasonable price? I have to say I think so. This is not a
trivial problem and this equipment isn't being manufactured by a dozen
companies and flying off Best Buy shelves. Given the low demand and difficult
requirements I think the price is reasonable. If your use case involves
smoothly switching between 2-4 high resolution dual head systems $480-$680
probably amounts to something in the range of 5-20% of the cost of the entire
system.

I don't buy the argument that this cost makes such a KVM pointless because one
can simply buy more display(s) and input devices instead: that takes a lot of
space and results in a lot of underutilized hardware.

------
arka2147483647
I think it's a two pronged demise

* Current display (DP, HDMP) and peripheral(USB) technology is complex, and probably is going to be expensive to switch in the fly without being unreliable.

* Virtual Machines and Remote Desktop solutions are good enough. Sure they can be a bit laggy sometimes, but good enough for most tasks.

So i guess that KVM switches are going to be more expensive to make, and there
are less customers who really need them...

------
reacweb
I think the use cases are disappearing. Using a KVM means working near many
noisy computers. I do not know the location of most of the machines I am using
remotely from my dumb windows PC. Poor guys that must use a KVM.

------
wastedhours
I still would like a personal one, I get to work from home frequently, and
have a personal desktop, personal laptop and work laptop that'd be great to
switch between without having to keep changing plugs (as it is, I velcro the
HDMI, mouse, keyboard and speaker jack together to keep it easy to handle).

------
xiconfjs
We are still using it in our testing environment - 8+ servers. We do a lot of
pre-OS tests so KVM is the optimal solution - faster and more reliable than
IPMI/etc.

------
huevo5050
There is a project to build an open source KVM-over-IP Rapsberry pi based.

rasky:

[https://www.nexlab.net/product/rasky/](https://www.nexlab.net/product/rasky/)

I have contributed to it but a lot of time without news. Maybe contribute to
rasky was risky.

------
JustSomeNobody
You can get a USB switch and a 4K HDMI switch for about $40.

I don't currently have a 4K HDMI switch, but my HD switch works just fine.
Sure you have two buttons to push (USB and HDMI), but it works and it's cheap.

~~~
cormman
Yep, I got this for my 4k monitor:
[https://www.amazon.com/gp/product/B071CJWSPF/](https://www.amazon.com/gp/product/B071CJWSPF/)

And this for my usb stuff: [https://www.amazon.com/Plugable-One-Button-
Swapping-Between-...](https://www.amazon.com/Plugable-One-Button-Swapping-
Between-Computers/dp/B006Z0Q2SI/)

It's under $25 total and both work perfectly well.

------
z3t4
One interesting use-case is having virtual machines with dedicated ports.

------
k__
Haha, those were the days!

I had one for my dual desktop setup back in the days.

Had a Windows and a Linux machine, but was too poor for second
mouse/keyboard/monitor. The Linux machine was some old PC I built from spare
parts.

I already had a switch that let me change the PC via ctrl+esc on the keyboard.

At my first job as a PC technician we still had the old ones with physical
switches.

------
frou_dh
The ones that used VGA ports for video often used to degrade the image quality
in comparison to a direct connection.

Frankly there are entire categories of desktop computer peripherals that get a
deserved reputation for being flakey junk. USB hubs used to be this way, but
presumably they've finally got those right. Inkjet printers too.

~~~
al2o3cr

        USB hubs used to be this way, but presumably they've finally got those right.
    

Not necessarily. I purchased a 10-port hub just a couple years back that was
internally three 4-port hubs chained serially. The OSX USB stack couldn't see
devices connected to the last four ports...

------
skriticos2
This does not surprise me at all. I have a 4k screen and just thinking about
all the fiddly bits between HDMI, HDCP and Freesync/Gsync between the computer
and the screen makes it quite difficult to build a switch. VGA was primitive,
but simple to switch, those times are gone. My computers usually make a fuss
if I just switch off the screen and back on, because both sides seem to have
some active signaling going on and way too much logic.

Ps: USB switches for the KM parts are rather simple though and there is a
healthy offering (+ you can build this yourself with some extension cords and
a simple USB switch). Also, more and more of my devices move wireless (e.g.
audio).

------
hyperfekt
As far as I am aware from the last time I tried to find such a thing the
packet-based interactive nature of modern display standards prevents the cheap
implementation of these devices, as opposed to the non-interactive, older
standards.

------
python-guy-vt
This tone of this article is pretentious and just plain douchey. The author is
largely assuming that their small niche (and petty) use case is what everyone
who uses a KVM would want (i.e. using a 4k monitor). The single largest use
for KVM is for servers, who the hell is wasting money on a 4k monitor for
their servers? There are plenty of reliable and affordable KVM's that the
author deems as old relics that work just fine for the large majority of
consumers.

~~~
npsimons
> This tone of this article is pretentious and just plain douchey.

I got that same feeling. First a "What?! KVMs are no longer sold at all?!"
followed by "wait, no, he's lying - KVMs are still sold, they just don't meet
_his_ standards." It's clickbait.

------
keypusher
The rise of more powerful graphics cards with the ports and ability to run
multiple monitors made this something that ever fewer desktop users need that
did before. You can still get good KVMs in the enterprise/hardware market,
they are common in server rooms, but even then less so than the old days as
most firmware allows remote management.

~~~
blauditore
I don't understand what this has to do with graphics cards. One is about
connecting multiple monitors to one computer, the other about connection one
monitor to multiple computers.

~~~
bitL
For example, my 3 monitors each have 4 different inputs. My GPUs have at least
3 outputs. So you can connect each GPU to each monitor, then you need a way to
switch between different computers at once or separately.

------
mancerayder
Are there any not-too-expensive, modern (as in DisplayPort-friendly and USB),
hardware KVMs available these days?

I started looking into a solution and I ended up shelling out money for
Synergy, which was cheaper than the HDMI-or-Displayport-I-forgot KVMs I saw on
Amazon, which looked like they were in the 2,300+ range (and with really poor
reviews).

------
petecox
I bought a USB2.0/VGA switch online for < $10. I had a number of vga and USB
type B (aka printer) cables lying in boxes that are now put to good use!

A windows laptop and a linux NUC, 5 USB peripherals shared.

4K and all digital HDMI might spell the death of it but I'd be needing new
PC(s) to drive such a display in any case.

------
linsomniac
This URL starts off with the condition that the KVM needs to be less expensive
than adding another display and keyboard, and operate at 4K. So this is
targeted towards the home environment? I'd guess that RDP/VNC and the like
have pretty much done away with the KVM in that environment.

------
dekhn
I am so happy I don't use KVMs any more. Instead, monitors with multiple
inputs, and a simple USB switch for the keyboard.Then I don't have to spend
$200 when I upgrade monitors, just so I can switch whatever new resolution I
moved to.

~~~
topspin
I've looked into doing this as well. Have you found monitors that a.) switch
inputs without many seconds of delay b.) switch using keyboard input as
opposed to banging on balky switches on two displays? My expectation is one
button and no delay, not switching the input devices and then switch two
monitors one after the other, because I expect to switch frequently. Also, the
buttons on a lot of monitors aren't really intended to be used terribly hard;
they wear out. Maybe capacitive buttons solve this, I guess, but those can be
flaky as well for other reasons.

~~~
dekhn
no, unfortunately all the monitors I use are slow (3-5 seconds) and the
keyboard switch takes 2-3 seconds.

------
tmdk
I think this is because people perceive multiple monitors as giving a better
overview, regardless of switches being available at a lower cost, which has
caused the market for switches to become a niche market.

------
sqldba
Jesus that author has a real attitude problem.

------
snarfy
All of our meeting rooms have computers with KVMs in case someone wants to use
their laptop on the big screen.

Or they can just remote in. It's kind of dumb.

~~~
gaius
How do you "just remote in" with no (working) OS?

~~~
petecox
'Smart' displays?

Where I worked they wall-mounted large screen TVs. Windows 10 casted to them
over wifi just fine.

------
eighthnate
I used to have a KVM to switch between my many boxes with many OSes. Now with
virtualization, I have box with a few virtual machines. Now if I want to use
windows, debian and freebsd, I don't have to switch between 3 physical boxes,
I just have to switch virtual machine windows on one box.

