os/doc/concepts/hosts.md

# Hosts

Nix flakes contain an output called `nixosConfigurations` declaring an
attribute set of valid NixOS systems. To simplify the management and creation
of these hosts, devos automatically imports every _.nix_ file inside this
directory to the mentioned attribute set, applying the projects defaults to
each. The only hard requirement is that the file contain a valid NixOS module.

As an example, a file `hosts/system.nix` will be available via the flake
output `nixosConfigurations.system`. You can have as many hosts as you want
and all of them will be automatically imported based on their name.

For each host, the configuration automatically sets the `networking.hostName`
attribute to the name of the file minus the _.nix_ extension. This is for
convenience, since `nixos-rebuild` automatically searches for a configuration
matching the current systems hostname if one is not specified explicitly.

You can set channels, systems, and add extra modules to each host by editing the
`nixos.hosts` argument in flake.nix. This is the perfect place to import
host specific modules from external sources, such as the
[nixos-hardware][nixos-hardware] repository.

It is recommended that the host modules only contain configuration information
specific to a particular piece of hardware. Anything reusable across machines
is best saved for [profile modules](./profiles.md).

This is a good place to import sets of profiles, called [suites](./suites.md),
that you intend to use on your machine.


## Example

flake.nix:
```nix
{
  nixos = {
    imports = [ (devos.lib.importHosts ./hosts) ];
    hosts = {
      librem = {
        channelName = "latest";
        modules = [ nixos-hardware.nixosModules.purism-librem-13v3 ];
      };
    };
  };
}
```

hosts/librem.nix:
```nix
{ suites, ... }:
{
  imports = suites.laptop;

  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;

  fileSystems."/" = { device = "/dev/disk/by-label/nixos"; };
}
```

[nixos-hardware]: https://github.com/NixOS/nixos-hardware