NixOS is highly configurable and also reproducible. We can use these features to build a bootable image which has all of the stuff we want and (hopefully) none of the stuff we do not want, such as:

• enable whatever offline software we want (for QR code scanning and so on)
  • bitcoin-qt, bitcoin-cli, bitcoin-tx, ...
  • offline version of iancoleman.io/bip39
  • offline version of codex32
  • offline version of Sparrow Wallet
• non-kernel - disable networking (including wifi/bluetooth)
• non-kernel - disable sound
• kernel - disable all networking devices (including any wifi/bluetooth)
• kernel - disable all audio input/output

Use nix to configure and build a custom NixOS image on a machine with internet access, burn to usb drive, and then run/install it on the airgapped machine.

1. Make sure you are on a system with at least Nix (the package manager) installed, with flakes enabled.¹
2. Clone this git repository.
3. Edit configuration.nix according to your preferences (see the comments in that file for help).
4. $ nix build .#nixos-airgapped-iso which will create an .iso file for you in ./result/iso
5. insert your usb thumbdrive and find out which /dev/X it is by running fdisk -l
6. $ sudo dd bs=4M if=/path/to/file.iso of=/dev/sdX status=progress oflag=sync
7. did you remember to replace the relevant parts of the above dd command?

1. Insert the usb thumdrive into the target device and turn it on.
2. Press F7 or whatever you need to (check your device manufacturer for this!) to access your system BIOS and make sure it boots from the usb thumbdrive.
3. You now have an "airgapped" NixOS system!

Please do your own research and be sure that this level of (imperfect!) "airgapping" is sufficient for your needs. It may not be.

If you are on NixOS, you can test things out in a virtual machine:

1. clone this repo and cd into it
2. build the vm: $ nixos-rebuild build-vm --flake .#nixos-airgapped
3. run the vm: $ ./result/bin/run-nixos-vm

1. NixOS Kernel - see "Custom configuration" section
2. airbuntu - how to build custom kernel to keep airgapped (ubuntu) pc offline
3. a thread with some links/resources