Multi-use computer Lab

[ahoekman]

Hello Group!
I am reaching out and hoping that I can get some help on a setup for a multi-use computer lab. I have a special lab that is used for Cisco CCNA classes. I have Dell 9020's running an i7 process and Windows 7 pro. These are our daily use machines that have general lab software like PacketTracer, MS Office, the network printer, Internet access, etc. I also have another round of similiar pc's on the floor that we use for our Linux classes, OS classes, and hardware classes to install os's on and then each person in the class has their own computer to use in a classroom environment to do labs etc. We now are using Raspberry Pi's in Linux classes, as well as Python classes and to do out reach with local schools. They typically interface Arduinos with either the Windows pc's or the Pi's if they are more advanced. I really want to be able to use a KVM switch to be able to switch between all the different pc's and the Pi's, but have not had much luck. We are using VGA KVM 4-port switches with a VGA to HDMI splitter. The biggest issue is that I can switch between devices, but then either video won't display properly with the Pi or the keyboard and mouse won't be recognized with the pc's. We also want the ability for our students (school groups who own their own) with their own Pi's to be able to come into the lab and use the keyboards, mice and monitors. Does anyone have any experience with this? Any advice would be really appreciative. Would like feedback before I spend a ton of money moving to another room with more hardware or replacing my KVM switches.

Thanks,
Annie

[ejolson]

I really want to be able to use a KVM switch to be able to switch between all the different pc's and the Pi's, but have not had much luck. We are using VGA KVM 4-port switches with a VGA to HDMI splitter. The biggest issue is that I can switch between devices, but then either video won't display properly with the Pi or the keyboard and mouse won't be recognized with the pc's.

It is unclear how things are connected from your discription. Did you mean a VGA to HDMI splitter or a HDMI to VGA splitter? I'm currently working in a similar room with two computers per monitor connected through KVM switchs and a seemingly random array of HDMI, display port, VGA and DVI converters. One set of PCs are apparently used to teach a course on computer security while the others are for regular use. My students use a bootable USB stick to load a network image of Linux on any of the computers and run diskless after that. It helps to make sure the KVM switch is set for the correct computer before booting so the keyboard, mouse and monitor get detected correctly. Switch the KVM to the other computer before booting the other one and so forth.

If you force the Raspberry Pi video output to HDMI at a particular resolution as a boot option, this may help solve your problem. Set hdmi_force_hotplug, hdmi_group and hdmi_mode as appropriate for your monitor in the config.txt file on your sdcard.

[ahoekman]

EJolson:

I would love to see a picture of your setup. I have had some upgrades to my room and we secured some funding for some new equipment in this room. I am getting new pc's that will have all HDMI outputs including monitors. I will have windows 10 on my main computers. I want to teach Linux on the Pi's, but not switch out all my hardware to hook up the pi's. I was using a StarTech Slim HDMI to VGA with the attached picture of KVM's.

thanks,
Annie

[ejolson]

I would love to see a picture of your setup.

I'm no longer in that room, but will try to get some pictures later this week. Congratulations on the funding and upgrades!

[tpyo kingg]

Use of a video display is not necessary with the Raspberry Pi's serial interface. I've done something similar long ago with a very tall stack of retired desktop hardware, but not RPis yet, though I sometimes use the serial interface on them. I chose the serial interface to avoid the problems and expense of graphics which you describe. The particular machines I had were set up for netboot and the router which they were connected to was customized using OpenBSD. The router could also target specific machines to serve up a choice of pre-loaded installation images as well as providing a proxy/cache for the packages and acting as a jump host. The key stage was to get OpenSSH running and then with that, it was possible to log in and work as normal using the router as a jump host. With the help of the remaining lab technician we built some relays that could be toggled remotely via shell scripts/aliases to turn on and off the machines using the router's GPIO connected to some relays (GPIO -> transistor -> relay -> fuse -> machine). I suppose if I were to try it again this decade I would use a UniPi or something similar to handle the wall current rather than building the entire relay board in-house.

However, although the Raspberry Pi can do netboot I'm not sure if it can handle net-based installation. Perhaps someone else can say. Maybe if it can't do it directly it could still net-boot a customized Busybox image and then use that to write the official raspbian image to the SD card, setting up serial and SSH interfaces along the way.

There are cheap USB-to-Serial cables and if you go that route you need to have ones that can be distinguished from one another so that you can reliably and predictably know which cable connects to which hardware.