2000 | 2001 | 2002 | 2003
2003
Grady:
Hey, y'all,
I'm getting a second machine at home, where the space is scant & the wiring
is not something I want to strain. I'd rather not get a second monitor, so
I figure a KVM switch is the likeliest alternative. I've read through the
discussions of KVM switches on the ALE list from last year & the previous,
which have been real helpful to me, since I've never used a switch before.
Since I suspect that such might be overkill just for two machines, I was
wondering if anybody had suggestions for any alternatives, since none has
occurred to me.
Michael:
Not overkill at all--it's an essential tool. Get a two port KVM switch. I
use a linksys at home and it is great. I user a 4 port Belkin at work and
it is good, too.
It's a lot cheaper than a second monitor, and a heck of a lot cheaper than
building a new room onto your house to hold all your computers.
Mike P:
If they are both running Linux you could just do a remote X session using GDM or XDM.
Its been awhile since I have set this up, but I could easily go through it again on one of my
machines at home and detail the steps I took if need be.
Mike L:
It wouldn't be overkill at all. Belkin and a few others make a 2
machine KVM that is pretty cheap, check out http://www.pricewatch.com
and see who has one on sale.
Side Note: Just remember that if you've got a Linux box and are running
X, you need to do a ctrl-alt-f(x) then alt-f7 everytime you switch the
KVM back to linux.
Jason:
I would actually really appreciate an overview on configuring remote X with GDM/XDM... If it's not too much trouble 
Michael:
That must be system specific. I've never had to to that in 4 years of
using a KVM with Linux.
Mike L:
Hmmm....weird. Might be somthing with slackware, since its the only
distro I've used with KVM's. Although I do know at the last job I had,
I know that the guys with redhat 7.x and Mandrake had to do it also.
Wonder why you haven't run into that issue. What distro or setup are
you using, etc...?
Josh F:
I wouldn't get a 2 port KVM unless they are substantially cheaper than
the 4 port. I don't know about you, but I keep having more and more
machines show up on my desk, and I kept an extra set of wires so I could
hook up a machine when my [mom's | friend's ] machine broke and showed
up on my doorstep
On a somewhat related note, has anyone had any luck with USB KVM
switches? I got one at work, but every time I switched away from the
linux box, I lost the connection to the mouse and keyboard. It was a
cheap KVM switch, so it may not have had the keyboard emulation that
nicer switches have.
Geoffrey:
This has never been my experience in using a linksys 4 device kvm for
about 8 years now.
Just hit the button on the kvm and I'm on the other box, monitor,
keyboard and mouse.
Jeff:
I've sworn by (and not AT) the larger Cybex units and I know they make
smaller four-way units that I expect should work just as well.
It's just that I've had booting problems with the fare available at the
likes of CompUSA (Linksys, Belkin) and to me that's just a showstopper.
Michael:
On Thursday 13 February 2003 12:22 pm, Mike Lockhart wrote:
> Hmmm....weird. Might be something with slackware, since its the only
> distro I've used with KVM's. Although I do know at the last job I had,
> I know that the guys with redhat 7.x and Mandrake had to do it also.
> Wonder why you haven't run into that issue. What distro or setup are
> you using, etc...?
Mostly RedHat and Mandrake--often highly customized so as to be almost
unrecognizable.
I would guess that it might happen with certain display cards or KVMs, but
none that I've used.
Michael:
I find the 2 port switches significantly more convienient to use. They
usually have some very simple way of toggling between the two computers.
The 4 ports are much less convenient. Of course, if you are going to have
more than 2 computers a 2 port isn't much good for you.
cfowler:
I have many linux machines in my office and only one has a head.
Unless you need X running on all machines, you can get away with just
running one with head. The rest are headless. I also turn on serial
console on all the other machines so If I do need to gain access to
/dev/console, I can do so with a null-modem cable. Works really well.
KVM still will not hurt. I've held off my purchase of a KVM due to the
fact I still think they are a little pricey for home use. I'm cheap
too.
JasonD:
On Thu, Feb 13, 2003 at 12:09:30PM -0500, Jason Vinson wrote:
> I would actually really appreciate an overview on configuring remote X with GDM/XDM... If it's not too much trouble
http://www.tldp.org/HOWTO/XDMCP-HOWTO/index.html
cfowler:
This is mainly due to keyboard emulation issues. If you have 4 machines
and the power goes off you may have problems booting back up. The main
reason is the fact that even those devices support emulation, they can
not service more than say 2 systems at a time with that emulation. So
if all 4 machines look for keyboard at once then the Belkin may have
issues servicing them at once. Problem is that if you want to get away
from this problem, You have to spend a little dough. Last week I demoed
a KVM IP device. It hooked directly up to a KVM switch and converted
its Video, and PS/2 outputs to IP. We demoed this device over the
internet. We have DSL connection. I was impressed with the speed.
I've tested other digital kvm boxes and were never impressed with
speed. This device was amazing. However it was also 3k so you can get
amazing stuff when you invest in good product.
Sean:
While trying to get away from OS/2 on a PIII and get Linux
installed on a dual boot P4 I got a Linksys dual-port KVM
and it worked flawlessly. Still does.
Sean:
On Friday 14 February 2003 12:27 am, cfowler wrote:
> This is mainly due to keyboard emulation issues. If you have 4 machines
> and the power goes off you may have problems booting back up. The main
> reason is the fact that even those devices support emulation, they can
> not service more than say 2 systems at a time with that emulation. So
> if all 4 machines look for keyboard at once then the Belkin may have
> issues servicing them at once.
This is easily solved by setting the BIOS on the machines so that they
stay OFF following power loss. Let them boot one at a time. It's a
lot less expensive than a high-end KVM.
David:
> I find the 2 port switches significantly more convienient to use.****
> The 4 ports are much less convenient.
What's less convenient about them? It's the same number of keystrokes to
switch between any computer....
Matt:
I think he's referring to some switches that basically only have a "next"
function where you press a button to go from PC 2 to PC 3, but if you want
to go from PC 2 to PC 1, you have to press it 3 times, and usually wait a
little bit inbetween presses.
I saw an ad for a 2-port kvm switch that consisted of nothing more than a
y-cable (http://www.ecost.com/ecost/shop/detail.asp?dpno=554209)... all of
the switching logic was built into a block in the cable where the ends
meet.. pretty low-profile.
Geoffrey:
I don't understand either. My linksys has a single button for each of
the four computers. It also supports keyboard shortcuts and will cycle
through each of the connected machines. I don't know what more you
could want.
Geoffrey:
> I think he's referring to some switches that basically only have a "next"
> function***
Gotcha. Well, as I noted my linksys had a button for each computer, one
push and you're there. Further keyboard shortcuts that would send you
to which ever machine you wanted as well.
Stephan:
If you have a high end monitor and if you use a high
pixel rate your image might degrade if you route the
signal through a kvm.
With one of my video cards the signal would even reflect from
the kvm back to video card and back to the kvm causing a shadow.
Using the pixel offset of the shadow, the pixel clock and
the light speed value I could calculate the cable length
between video card and kvm.
Not really useful so I dismantled my physics project.
Joe:
Don't get a cheap one. I made that mistake and fried the power
supply in one of my boxes. I don't know what the technospeak
term is, but you need one that will provide the proper kbd and
mouse electrical characteristics even when the switch is
switched away from a particular machine.
Geoffrey:
> Don't get a cheap one. ****
Correct. What the kvm does is make each machine see a mouse/keyboard
whether or not it's the selected one. If it doesn't do this properly,
ps2 mice get lost. In both X and windows when you return, the mouse
will be lost. Serial mice are more forgiving, or should I say the
serial port is.
Michael:
With my Linksys 2 port I just tap the Control key twice to switch. When I
had a Linsys 4 port it was some sctrange control-something followed by the
number I want to switch to. So I actually have to think about which
screen I want to change to and remember the proper key combination.
Same thing with my Belkin 4 port. I need to scrolllock-scrolllock-n when n
is 1, 2, 3, or 4. I need to know where I'm going. I often get it wrong.
But I never get it wrong with the 2 port linksys and it is faster, too.
Synco:
actually, 2-port kvm switches were a lot cheaper than switches with 4
ports and they seem to get exponentially more expensive... try to price a nice
10-port one. i don't really understand why they're so expensive... i
could probably make one from radio shack parts for about $30, but it would
be ass ugly.
i have the same problem... keep getting new machines, but i've found the
best way (for me anyway) is to just boot them from the network and load
the root fs from NFS... then i can ssh/rsh to any of the machines on my
lan easily... that also gives you some flexibility as far as what you'll
be using the machines for.
for instance, to run your distributed processing cluster, you could load a
certain NFS root, but if you wanted your machines to do their normal
everyday jobs, they could load their own individual or group-based NFS
root. of course this can all be done from a single machine. kvm switches
don't give you that kind of flexibility.
just a kvm-switch alternative for those of you as broke as me.
Greg:
Try buying the old mechanical KVM switches (4 port) for about $10.00 . If
needed, you can buy any adapters for the back for about $1.50/ea. Total
price:$16.00 . That is what I did for my last one KVM switch. Works fine
with RH Linux and OpenBSD.
2002
Jeff:
At this point, Cybex is the only KVM switch I'll buy
Geoffrey:
I've had a linksys kvm which I've used for about 4 years now. It's
worked with everything. It's connected to my viewsonic monitor, linux
cool keyboard and logitech wheeled mouse. All works well, although all
that's connected to it now is Linux.
Jeff:
Last place I worked, I requested a Cybex KVM switch for a new server
rack; "Batman and Robin" bought me a Belkin instead. The machines - a
mixture of Compaq Deskpros and Dell Poweredges - wouldn't all boot up
properly when they weren't selected. I told the Dynamic Duo to get my a
frickin' Cybex. They sent me a Belkin;[Oops, I meant to say that they sent me a Linksys the second time.] same issues. I sent it back to
the Caped Crusaders and FINALLY they sent me the Cybex I'd originally
asked for. No issues and no problems.
Some years prior after I had bought a Cybex at work, I found I had a
problem with an IBM PS/2 Model 80 and the keyboard. Cybex sent me an
adapter box (at no cost) that corrected an issue with original PS/2s and
I was in business.
2001
Joe:
Displaying my ignorance... again...
Today I got a 4-port KVM switch. It doesn't have a keyboard
emulation circuit; the instructions said, "unplug the keyboard
from your computer and plug it back in; if the machine still
responds to the keyboard then it will work with this switch."
So I did that (thinking even at the time that I'd heard
somewhere it wasn't a good idea, but what the hell, I'm
following instructions, right?) And the instant I pulled
the keyboard connector out the machine died - powered off. And
wouldn't power on again. Power supply is dead. (Amazingly enough,
the motherboard is uninjured - moved it to another case and
it booted fine.)
So is this behavior I should have expected? I'm very hesitant
to try using the KVM switch with any of my machines now,
since switching machines is the moral (and electrical)
equivalent of unplugging the keybord. Incidentally, it
was an AT keyboard connector, on an AT motherboard, if that
matters.
Jenn:
<putting on tech hat...oooh...dusty>
AT motherboards in general respond very poorly to having their keyboards removed
while powered on. ATX, as far as I know, doesn't have this problem.
That being said, I've never had a problem with AT machines on a non-intelligent
switch...
Here's the dance I go thru, without any ill effects (AT and ATX, Belkin OmniCube
KVM and some old ABCD rotating dial KVM)...
- select port 1 on KVM
- power on machine attached to port 1
- wait for POST to detect keyboard...or get all the way to a prompt and log in
if you're paranoid
- switch to port 2 on KVM
- power on machine attached to port 2
shake, stir, repeat
Once everything is booted and humming along, you should be able to switch
between them with no problems. It's not exactly the same thing as yanking the
cable from the back of the computer.
Short answer: power dying is a lucky (because it should've been your
motherboard) but expected consequence of removing the keyboard cable from the AT
motherboard, so don't do it again. 
As long as you don't yank the cable out,
you should be able to switch to your heart's content. And I think I may have
some spare AT motherboards lying around if my advice causes a catastrophic
loss.......
Geoffrey:
I've gone the route with these switches and I'll say that if you want to
do this, you should get one of the more expensive ones that contain
electronics that 'fools' the machine into thinking it's still
connected. I've got a 4 port Linksys that I've been using for about 4
years now. I don't remember how much it was, but I'm pretty sure it's
in the $70-$100 range. They are pricing, but the bloody work and they
don't wear out. I had a couple of mechanical switches before this, and
they all got flaky after a while.
I've never heard or experienced the problem you've outlined below
though. I have had my switch loose power and when it does, the mouse
and keyboard would not respond. If I switched from one machine to
another, I'd get the keyboard back, but the mouse would not return
(that's in X) so I would end up having to restart X.
By the way, the linksys switch I have controls the monitor, keyboard and
mouse. It enables you to switch from one machine to another via buttons
on the front of the switch as well as a set of key sequences. It also
has a mode where it will rotate through all systems it's connected to.
Seems like something you might use for a security system, but not
something I ever take advantage of. They also make larger switches, I
think up to 7 or 8 boxes.
Greg:
To put in my 2 cents worth, I would heartily suggest what "Wandered Inn"
said about getting the good stuff. My company (total MS shop) has had an
ongoing problem w/ KVM's that lose the mouse connection. That seems to be
the rule in my experience regardless of p.c. or os that is used. Like jenn
said I religiously log in before I ever switch, otherwise the p.c. doesn't
seem to pick up a component. My LinkSys ProConnect 4 port does that and so
I just live with 4 mice on my desk (at least until I get my rack up
tomorrow).. and 2 at work (one for my Linux box and the other for the NT
2000 box), but the monitor and keyboards seem to work fine. What they are
using at work are Masterviews and can be had at Cyberguys 1.800.892.1010 or
www.cyberguys.com . Mine and just about all that I see have ports for both
AT and the PS/2 connections. I would also recommend one that comes with
some type of switching the power over "gently". Some come with cables or
you can get them at Office Depot or anywhere else. The sysadmins at work
swear that they work, but I haven't been in the server room in a while, so I
can't personally support that claim.
Geoffrey:
Let me get this right. You lose your mouse when you switch your
proconnect? That's the same box I've got and I've never lost the mouse,
unless the proconnect looses power. I've run both ps2 and serial mice
to this thing. Once even ran the ps2 from the computer to the serial of
the proconnect and that worked.
Jeff:
In response to my request for a Cybex KVM switch, our IT people bought
me first a Belkin and then a Linksys switch. Neither handled the
machines I connected it to correctly - Dell PowerEdge severs. I finally
put my footdown and insisted on the Cyber 8-port and finally, joy was
achieved, as I knew it would be.
In an earlier experience, Cybex sent me a special adapter to permit
proper operation with an IBM PS/2 system, free of charge. I've never
forgotten that, and I honor them with my continued patronage.
Joe:
Thanks for the advices, everyone. I got this KVM on eBay
for $30, including a complete set of cables, and I'm not
all that interested in upgrading to something less cheesy.
I'll probably just keep a keyboard per machine; it
was moving the monitor around that was really driving
me up the wall, anyhow.
2000
Nicodemus:
I'm running RedHat 5.2 on a P133 with a serial mouse and Windows 98 on
a PIII/550 with a PS/2 mouse. I have a 4-port KVM switch that I'm
using and everything works fine except for the mouse.
I have a Logitech Trackball that runs fine for the Windows machine,
but I can't get it to work with my Linux box. I've tried running
mouseconfig and selecting a variety of different types and nothing has
worked. It's not that big a deal having to use two mice. The main
reason for the KVM was the keyboard and monitor, but it sure would be
nice to use the trackball I'm in love with on my Linux box.
Does anyone have any ideas how I can remedy this situation?
Geoffrey:
First of all, you've got Linux on the wrong machine.
Have you tried this mouse connected directly to your Linux box? (that
is, ruled out the possibility that it's the switch box that's the
problem...)
Patrick:
Are you booting with the switch turned to each machine as it boots? Most
switches will not send ps2 or serial sigs to the machines unless there is a
physical connection.
Boot one box with the switch turned to it, the mouse should work.
switch boxes, boot up and that mouse should work... If you can't get this
far, the the switch or the mouse is bad.
otherwise you should now be able to switch between the two.
Marc:
If you have a 'hard' switchbox not a electronic one this is
most likely your problem. Even amongst the electronic ones
you get what you pay for, be careful. (1.)
Also if your switch has ports for both PS/2 and Serial mice
it will normally only support 4 of one type or the other,
you cannot mix-n-match amoung the servers.(2)
If I have to have them, I only use Rartians - never had a
problem with them. If you do have a 'hard' switch and no
budget to buy a really good one Rartian sells a 'dongle'
with KB and M leads that you can plug into the back of your
server. It provides the heartbeat to the ports so everything
will work and you can hotplug KB and Mice into the dongle.(3)
The dongles arn't nearly as expensive and much cheaper then a
hung server
Geoffrey:
(1.)This is true, my box was relatively expensive, requires it's own power
and has cute little leds telling you the state of each machine. A few
other bells/whistles as well.
(2)This does not apply to the box I have. It has both ps/2 and serial
mouse ports of which I've mixed and match with no problems.
(3)Mine's a linksys, and I've never had a problem with it. I went through
about 5 of the cheap boxes before I got this one.
Geoffrey:
Patrick wrote:
> Are you booting with the switch turned to each machine as it boots? Most
> switches will not send ps2 or serial sigs to the machines unless there is a
> physical connection.
This depends on the switch. I've got a 4 way switch that makes it look
like (to the machine) that there is a keyboard and mouse attached
regardless of the position of the switch. I can boot any one of them
while my switch is set to any other. Depends on how smart the switch is
(generally reflected in the price as well). You probably don't want to
be changing the switch in mid boot regardless of the switch.
> Boot one box with the switch turned to it, the mouse should work.
This might help determine how smart the switch is. If it does work, the
switch is not that smart. If it doesn't work, you've really not learned
anything yet.
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