42LoCo42 / und

micro nix deployer - soon to be rewritten

µnd - micro nix deployer

Inspired by nixos-anywhere and nixinate, this tool enables you to install and update a NixOS configuration on any system with SSH and root access and some basic tools.

Rewrite in progress - currently happening in Aquaris!

Usage

{
  inputs = {
    # the installation uses disko to prepare the disks
    disko.inputs.nixpkgs.follows = "nixpkgs";

    und.url = "github:42loco42/und";
  };

  outputs = { self, nixpkgs, ... }: {
    apps = self.inputs.und.und self;
    nixosConfigurations = {
      test = {
        system = "x86_64-linux";
        modules = [
          ./disk.nix # disko config file

          self.inputs.disko.nixosModules.disko

          {
            _module.args.und = {
              host = "example.org";
              user = "foobar";

              # set this option if the user on the old system (which will be overwritten)
              # is different from your normal user
              # preUser = "barbaz";

              # set this option to use a custom kexec tarbarll URL
              # otherwise, the default tarball for the config's system
              # from https://github.com/nix-community/nixos-images will be used
              # kexec = "https://example.org/other-kexec.tar.gz"
            };
          }
        ];
      };
    };
  };
}

Modes of operation

For a configuration named test (like in the example above), these are the primary ways to use the script:

nix run .#test -- -i # installs to the target system
nix run .#test       # updates the target system

nix run .#test -- -l -i # installs to the local system (e.g. from a NixOS live ISO)
nix run .#test -- -l    # updates the local system

Other options

The following options are also available:

• -u, --user: override the user option
• -h, --host: override the host option
• -p, --preUser: override the preUser option
• -k, --kexec: override the kexec option
• --no-format: don’t format the disks (e.g. to retry a failed installation)
• --no-kexec: don’t perform the kexec steps (e.g. when the target is already running a NixOS live environment)
• --no-reboot: don’t reboot after the installation has finished (e.g. to configure more stuff)
• --save-hwconf <path>: generate & save a hardware configuration file to <path>. The script will then pause to allow further edits and actions (e.g. adding the file to git)

Notes

• all remote builds happen on the target system to allow installing to different architectures
• all SSH connections have a PTY, so you can enter passwords