flatten nixos-install tutorial slug

use 'nixos-install-flake' as slug, to distinguish it from 'nixos-install' command'

will setup redirect in cloudflare soon.

en/tutorial/nixos-install/configuration-as-flake.md → en/configuration-as-flake.md

@@ -1,7 +1,3 @@
----
-slug: en/configuration-as-flake
----
-
 # Convert `configuration.nix` to be a flake
 
 A problem with the default NixOS `configuration.nix` generated by the official installer is that it is not "pure" and thus not reproducible (see [here](https://www.tweag.io/blog/2020-07-31-nixos-flakes/#what-problems-are-we-trying-to-solve)), as it still uses a mutable Nix channel (which is generally [discouraged](https://zero-to-nix.com/concepts/channels#the-problem-with-nix-channel)). For this reason (among others), it is recommended to immediately switch to using #[[flakes]] for our NixOS configuration. Doing this is pretty simple. Just add a `flake.nix` file in `/etc/nixos`:

en/tutorial/nixos-install.md → en/nixos-install-flake.md

@@ -97,7 +97,7 @@ $ which nvim
 
 ![[configuration-as-flake]]
 
-Let's store our whole configuration in a [[git]] repository.
+Let's [[configuration-as-flake|store our whole configuration]]# in a [[git]] repository.
 
 {#git}
 ## Store the configuration in Git

en/nixos.md

@@ -4,7 +4,7 @@ NixOS is a Linux distribution based on the [[nix]] package manager.
 
 ## Getting Started
 
-See our tutorial: [[nixos-install]]
+See our tutorial: [[nixos-install-flake]]
 
 ```query
 children:.

en/tutorial.md

@@ -6,7 +6,33 @@ order: -100
 
 - [[nix-rapid]]#
 - [[nixos]] tutorial series
-  - [[nixos-install]]
+  - [[nixos-install-flake]]#
   - [ ] ...
 - [[nixify-haskell]]
 
+## Scratch
+
+- Nix series
+- Ext nixpkgs using `nix *`
+    - `nix run`, `nix shell`, `nix profile install` (fn - hm)
+      - eg: run redis (or lsd with yaml)
+  - Rapid introduction to flakes
+  - evalModules
+    - Example 1: generate [redis.conf](https://redis.io/docs/management/config-file/) and returns drv with conf file only
+      - consider cluster
+    - Example 2: ... returns shell script that runs redis with that conf file
+      - add `package = pkgs.redis`; output would include writeShellApplication derivaiton
+    - ultimately, people can just `nix run` it.
+  - flake-parts
+- System series
+  - NixOS ...
+    - install
+    - basics:
+    - services:
+  - home-manager ...
+    - Basics: install, packages, dotfiles, ..
+    - Advanced: run services (ubuntu + macos)
+      - try with our redis above
+      - show official redis module (if there's any)
+- Dev series
+  - Haskell series