Table of Contents
Hardware
I have just setup a PiKVM, here’s the Amazon link for the KVM hardware (case and Pi hat etc) and here’s an Amazon link for a Pi4 to match.
The PiKVM web site has good documentation [1] and they have a YouTube channel with videos showing how to assemble the devices [2]. It’s really convenient being able to change the playback speed from low speeds like 1/4 original speed) to double speed when watching such a video. One thing to note is that there are some revisions to the hardware that aren’t covered in the videos, the device I received had some improvements that made it easier to assemble which weren’t in the video.
When you buy the device and Pi you need to also get a SD card of at least 4G in size, a CR1220 battery for real-time clock, and a USB-2/3 to USB-C cable for keyboard/mouse MUST NOT BE USB-C to USB-C! When I first tried using it I used a USB-C to USB-C cable for keyboard and mouse and it didn’t work for reasons I don’t understand (I welcome comments with theories about this). You also need a micro-HDMI to HDMI cable to get video output if you want to set it up without having to find the IP address and ssh to it.
The system has a bright OLED display to show the IP address and some other information which is very handy.
The hardware is easy enough for a 12yo to setup. The construction of the parts are solid and well engineered with everything fitting together nicely. It has a PCI/PCIe slot adaptor for controlling power and sending LED status over the connection which I didn’t test. I definitely recommend this.
Software
This is the download link for the RaspberryPi images for the PiKVM [3]. The “v3” image matches the hardware from the Amazon link I provided.
The default username/password is root/root. Connect it to a HDMI monitor and USB keyboard to change the password etc. If you control the DHCP server you can find the IP address it’s using and ssh to it to change the password (it is configured to allow ssh as root with password authentication).
If you get the kit to assemble it (as opposed to buying a completed unit already assembled) then you need to run the following commands as root to enable the OLED display. This means that after assembling it you can’t get the IP address without plugging in a monitor with a micro-HDMI to HDMI cable or having access to the DHCP server logs.
rw systemctl enable --now kvmd-oled kvmd-oled-reboot kvmd-oled-shutdown systemctl enable --now kvmd-fan ro
The default webadmin username/password is admin/admin.
To change the passwords run the following commands:
rw kvmd-htpasswd set admin passwd root ro
It is configured to have the root filesystem mounted read-only which is something I thought had gone out of fashion decades ago. I don’t think that modern versions of the Ext3/4 drivers are going to corrupt your filesystem if you have it mounted read-write when you reboot.
By default it uses a self-signed SSL certificate so with a Chrome based browser you get an error when you connect where you have to select “advanced” and then tell it to proceed regardless. I presume you could use the DNS method of Certbot authentication to get a SSL certificate to use on an internal view of your DNS to make it work normally with SSL.
The web based software has all the features you expect from a KVM. It shows the screen in any resolution up to 1920*1080 and proxies keyboard and mouse. Strangely “lsusb” on the machine being managed only reports a single USB device entry for it which covers both keyboard and mouse.
Managing Computers
For a tower PC disconnect any regular monitor(s) and connect a HDMI port to the HDMI input on the KVM. Connect a regular USB port (not USB-C) to the “OTG” port on the KVM, then it should all just work.
For a laptop connect the HDMI port to the HDMI input on the KVM. Connect a regular USB port (not USB-C) to the “OTG” port on the KVM. Then boot it up and press Fn-F8 for Dell, Fn-F7 for Lenovo or whatever the vendor code is to switch display output to HDMI during the BIOS initialisation, then Linux will follow the BIOS and send all output to the HDMI port for the early stages of booting. Apparently Lenovo systems have the Fn key mapped in the BIOS so an external keyboard could be used to switch between display outputs, but the PiKVM software doesn’t appear to support that. For other systems (probably including the Dell laptops that interest me) the Fn key apparently can’t be simulated externally. So for using this to work on laptops in another city I need to have someone local press Fn-F8 at the right time to allow me to change BIOS settings.
It is possible to configure the Linux kernel to mirror display to external HDMI and an internal laptop screen. But this doesn’t seem useful to me as the use cases for this device don’t require that. If you are using it for a server that doesn’t have iDRAC/ILO or other management hardware there will be no other “monitor” and all the output will go through the only connected HDMI device. My main use for it in the near future will be for supporting remote laptops, when Linux has a problem on boot as an easier option than talking someone through Linux commands and for such use it will be a temporary thing and not something that is desired all the time.
For the gdm3 login program you can copy the .config/monitors.xml file from a GNOME user session to the gdm home directory to keep the monitor settings. This configuration option is decent for the case where a fixed set of monitors are used but not so great if your requirement is “display a login screen on anything that’s available”. Is there an xdm type program in Debian/Ubuntu that supports this by default or with easy reconfiguration?
Conclusion
The PiKVM is a well engineered and designed product that does what’s expected at a low price. There are lots of minor issues with using it which aren’t the fault of the developers but are due to historical decisions in the design of BIOS and Linux software. We need to change the Linux software in question and lobby hardware vendors for BIOS improvements.
The feature for connecting to an ATX PSU was unexpected and could be really handy for some people, it’s not something I have an immediate use for but is something I could possibly use in future. I like the way they shipped the hardware for it as part of the package giving the user choices about how they use it, many vendors would make it an optional extra that costs another $100. This gives the PiKVM more functionality than many devices that are much more expensive.
The web UI wasn’t as user friendly as it might have been, but it’s a lot better than iDRAC so I don’t have a serious complaint about it. It would be nice if there was an option for creating macros for keyboard scancodes so I could try and emulate the Fn options and keys for volume control on systems that support it.
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