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USB Passthrough

For USB keyboards and mice connected to PiKVM directly, USB passthrough allows forwarding their input to the host system. This feature is available for all versions of PiKVM except the DIY version based on Pi Zero. It works best with HDMI passthrough available on PiKVM V4 Plus.

Let's consider this setup:

  • PiKVM V4 Plus connected to PiKVM switch;
  • A keyboard and a mouse connected to USB A ports on the PiKVM;
  • An external display connected to the PiKVM directly using HDMI out.

Example setup

With both HDMI passthrough and USB passthrough enabled, you would be able to do this:

  • Switch between Computer 1 and Computer 2 connected to PiKVM Switch;
  • Control them directly from this single keyboard/mouse pair (in addition to remote control);
  • See the video output from the selected host on the local display.

Enabling USB passthrough

Follow these steps to enable USB passthrough on your PiKVM:

  1. Log into your PiKVM as root, either via SSH, web console, or USB serial connection.

  2. You need KVMD 4.74+ to be able to use this feature. Update the PiKVM OS as root:

    [root@pikvm ~]# pikvm-update

  3. PiKVM will reboot, log in as root again.

  4. Run the following command to change acces to read-write, enable USB passthrough, and change acces to read-only again:

    [root@pikvm ~]# rw; systemctl enable --now kvmd-localhid; ro

Once you've done that, you should be able to use your USB keyboard and mouse connected directly to your PiKVM to control the host.

Toggling USB passthrough

Every once in a while you may want using keyboard/mouse to control your PiKVM instead of controlling a host. Once USB passthrough is enabled in the system, you can switch it on and off with shortcuts:

  • LeftAlt, LeftAlt, K (mnemonic KVM) disables keyboard/mouse grabbing and allows using the input devices with PiKVM locally, for example, for the console operating.

  • LeftAlt, LeftAlt, H (mnemonic Host) switches back to the passthrough mode and passes keyboard-mouse events to the host.

Press these keys immediately one after another: LeftAlt, then LeftAlt again, then the mnemonic key.

Switching the PiKVM Switch channels

If you have one or two PiKVM Switches, you can use LeftAlt, LeftAlt, 1 (1-8) to switch between up to 8 channels.

For three or more PiKVM Switches, you need to use double numbers, e.g., LeftAlt, LeftAlt, 3, 2 (unit 3, channel 2).