docs: add 'System management with nix flakes' guide

site/src/SUMMARY.md

@@ -11,6 +11,7 @@
   - [Define a Module in a Separate File](./define-module-in-separate-file.md)
   - [Define Custom Flake Attribute](./define-custom-flake-attribute.md)
   - [Dogfood a Reusable Flake Module](./dogfood-a-reusable-module.md)
+  - [System management with nix flakes](./nixos-flake.md)
 - [Explanation]()
   - [Overlays](./overlays.md)
 - [Reference Documentation]()

site/src/nixos-flake.md

@@ -0,0 +1,130 @@
+# System management with nix flakes
+
+If your goal is to control your machine using [nix flakes](https://nixos.wiki/wiki/Flakes), this guide is for you.
+
+Machines come in different flavors, you may already be using nixos, another linux distribution or mac (with arm or intel architecture). You can manage them all using "the flake way".
+
+Be sure to have nix installed in your system.
+
+Let's start!
+
+## Terminology
+
+- `host`: a machine, like a desktop computer, a laptop or a server in the cloud
+- `hostname`: name given to the machine, use `hostname -s` to retrieve it in unix systems
+- `templates`: in this context they refer to nix templates
+
+## Getting started
+
+All of our configurations will be conveniently housed within a `nixos-config` folder, irrespective of the underlying system being used.
+
+No matter the system used, we are gonna create a folder that will contain all the configurations for the host system. You have the option to back up the project on a Git platform such as GitHub, GitLab, Gittea, and others. Additionally, you can easily extend it to multiple hosts if needed.
+
+Let's begin
+
+```sh
+mkdir ~/nixos-config
+cd ~/nixos-config
+```
+
+And we are going to initialize the fantastic [nixos-flake](https://github.com/srid/nixos-flake) which uses itself flakes-parts.
+
+```sh
+nix flake init -t github:srid/nixos-flake
+```
+
+This will initialize a flake with support for nixos, nix-darwin and home-manager combined.
+
+If you'd rather initialize only a macos, or another linux distribution, check the [nixos-flake docs](https://zero-to-flakes.com/nixos-flake/templates).
+
+## Configuring different systems
+
+### On nixos
+
+Your nix configuration should be on `/etc/nixos`, you should have something like:
+
+```console
+$ ls /etc/nixos
+configuration.nix  hardware-configuration.nix
+```
+
+Let's copy the existing system there.
+
+```sh
+TARGET="~/nixos-config/hosts/$(hostname -s)"
+mkdir -p "$TARGET"
+cp -r /etc/nixos "$TARGET"
+```
+
+Now it's time for you to dig into the `flake.nix`, update the `TODO`s with your `username` and `hostname`, and
+finally, import the configurations that we previously copied.
+
+The last step is to activate the flake:
+
+```sh
+nix run .#activate
+```
+
+### On other linux distributions
+
+If you are using a non-nixos linux distribution, you probably should use the `home` template (you can add other systems later). And you'll use nix as a replacement for your dotfiles, with the advantage of having a declarative language, with declarative aliases, packages from nixpkgs and many more configurations.
+
+```sh
+nix flake init -t github:srid/nixos-flake#home
+```
+
+Configure at will.
+
+And finally, activate it:
+
+```sh
+nix run .#activate-home
+```
+
+### On Mac
+
+If you are on an Intel Mac, change `mkARMMacosSystem` to `mkIntelMacosSystem` and run
+
+```sh
+nix run .#activate
+```
+
+## Folder structure
+
+You can use this set up as a starting point for a multi-machine and multi-user configuration for your fleet of machines.
+
+```sh
+nixos-config/
+├── hardware/
+│   ├── sd-image/
+│   └── dell-xps13.nix # example of a specific hardware
+├── home/
+│   └── default.nix # shared home config
+├── hosts/
+├── nix-darwin/
+│   └── default.nix
+├── nixos/
+│   └── default.nix
+├── users/
+│   ├── config.nix
+│   └── default.nix
+├── flake.lock
+└── flake.nix
+```
+
+inside the `hosts` you'd create a "host" combining a user + home + nixos* + nix-darwin* + hardware\*
+
+\* optional, depends on your needs
+
+## Getting help
+
+For questions related to flake-parts head to the [flake-parts discussions](https://github.com/hercules-ci/flake-parts/discussions) on github.
+
+For questions related to nixos-flake head to the [nixos-flake discussions](https://github.com/srid/nixos-flake/discussions) on github.
+
+
+## Resources
+
+- https://github.com/srid/nixos-config
+- https://github.com/lovesegfault/nix-config
+- https://nixos-and-flakes.thiscute.world/nixos-with-flakes/modularize-the-configuration