This directory will store all the systems and their machine settings to use in the modules.
The systems directory is where all the systems are stored. They are divided by category. So an example for a system is a Thinkpad, this is a laptop. So it’s configuration file is stored at /systems/laptops/thinkpad/.
NixOS/
├── systems/
│ ├── category/
│ │ ├── specific-machine/
│ │ │ ├── configuration.nix
│ │ │ ├── hardware-configuration.nix
│ │ │ └── settings.nix
│ │ ├── ...
│ │ └── common-settings.nix
│ ├── ...
│ └── common-settings.nix
│ ...
Every system has a few common files. These are: default.nix, hardware-configuration.nix, and settings.nix.
First, default.nix is what gets loaded when a system get’s loaded. In this file, you have the possibility to write overriding configuration options though this is discouraged. I’d recommend writing a module instead, and adding a setting for it in /systems/common-settings.nix and then enabling it for that machine.
Next, hardware-configuration.nix is created when you first boot into NixOS, and I’d recommend you just paste that into the folder of that machine. I’d also recommend editing it unless you know what you’re doing.
Lastly, settings.nix is where the settings can be overwritten for a particular machine. An example of a setting I would override is system.hostname, as every machine needs it’s own hostname. if you leave a setting out of this file, it will go to the defaults of that category. That is why /systems/category/common-settings.nix exist. Here you can override settings for all machines of that category. The category settings, when unspecified in turn go to the overal system settings in /systems/common-settings.nix.
Settings are what loads and unloads modules. The settings have the following schema:
{
users = { ... };
system = { ... };
}
To learn more see system modules, or user modules for more information about the settings you can use and apply.