Ask HN: Control 2 air-gapped computers with 1 mouse and keyboard

Re:Ask HN: Control 2 air-gapped computers with 1 mouse and k... by NitpickLawyer on Monday October 27, 2025 @06:05AM (#45719179)

First, before you do anything you should check if you even should do this. Modern peripherals may have local storage (for drivers and such) and they may be visible (even automounted) by the OS. In that case your risk profile may not allow it (see stuxnet). Also be aware that sharing one keyboard will make you prone of brainfarting and muscle memory your credentials from one PC to the other. Depending on the reason behind airgapping, that may or may not be frowned upon.

Anyway, I use a "dumb" version of this setup, out of convenience. I have a dumb USB switch, with only one host connector. I use 2 cables, and have them tied together with a binder paperclip thingy. On the (rare for me) occasion I need to switch, I just unplug one cable and plug the other.

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Re:Ask HN: Control 2 air-gapped computers with 1 mouse and k... by WorldDev on Monday October 27, 2025 @09:10AM (#45720646)

That's interesting, thanks for sharing.

> Modern peripherals may have local storage

Do you mean the flash that contains the code for the microcontroller?

> I have a dumb USB switch

I am not 100% sure I understood. Is the "dumb USB switch" the paperclip?

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Re:Ask HN: Control 2 air-gapped computers with 1 mouse and k... by NitpickLawyer on Monday October 27, 2025 @09:42AM (#45720966)

No, dumb as in it only has one "host" connection, and many peripheral ports. So I put all my stuff there, but it can only be connected to one host at a time. So instead of a switch, I use the cables. Unplug one, and plug the other. Almost the same effort.

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Re:Ask HN: Control 2 air-gapped computers with 1 mouse and k... by WorldDev on Monday October 27, 2025 @11:45AM (#45722302)

I see, you are unplugging and re-plugging, instead of just pressing a button. That makes sense. It feels like a usb mechanical switch should exist, but I guess it does not.

Another option that I looked at is whether I could use the switching capability on the device itself. For example the new Logitech MX 4 can switch between different computers. It also has a wireless connection, versus bluetooth connection. Do you have a sense whether switching with a device like that is enough of a separation?

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