feat: migrate the content from thiscute.world into the repo

docs/introduction/advantages-and-disadvantages.md

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+
+### Advantages of Nix
+
+- **Declarative configuration, Environment as Code, can be managed with Git**
+  - Nix Flakes lock dependences's version through a lock file named `flake.lock`, to ensure that the system is reproducible. This idea actually borrows from some package managers such as npm, cargo, etc.
+  - Compared with Docker, Nix Flakes provides a much stronger guarantee for the reproducibility of build results, because Dockerfile is actually an imperative configuration and there is no such thing as `flake.lock` in Docker, Docker's reproducibility relies on sharing the build result(which is MUCH MORE LARGER than Dockerfile itself) through image registry(e.g. Docker Hub).
+- **Highly convenient system customization capability**
+  - By changing a few lines of configuration, various components of NixOS can be easily customized. This is because Nix encapsulates all the underlying complex operations in nix packages and only exports concise and necessary declarative parameters.
+  - Moreover, this modification is very safe. For example, switching between different desktop environments on NixOS is very simple and clean, you just need to change several lines of the configuration.
+- **Rollback**: The system can be restored to any historical state at any time(except the state that are NOT managed by NixOS, such as docker containers, postgresql data, etc...), and NixOS even adds all old versions to the boot options by default to ensure that the system can be rolled back at any time even though it crashes. Therefore, NixOS is also considered one of the most stable Linux Systems.
+- **No dependency conflicts**: Because each software package in Nix has a unique hash, its installation path also includes this hash value, so multiple versions can coexist.
+- **The community is very active, and there are quite a few third-party projects**. The official package repository, nixpkgs, has many contributors, and many people share their Nix configuration on Github/Gitlab. After browsing through it, the entire ecosystem gives me a sense of excitement in discovering a new continent.
+
+
+### Disadvantages of Nix
+
+- **High learning curve:**: If you want the system to be completely reproducible and avoid pitfalls caused by improper use, you need to learn about the entire design of Nix and manage the system in a declarative manner. You cannot blindly use `nix-env -i` (which is similar to `apt-get install`).
+- **Chaotic documentation**: Flakes is still an experimental feature, and there are currently few documents introducing it, Most of the Nix community's documentation only introduces the old cli such as `nix-env`/`nix-channel`. If you want to start learning Nix directly from Flakes, you need to refer to a large number of old documents and extract what you need from them. In addition, some of Nix's current core functions are not well-documented (such as `imports` and Nix Module System), to figure out what it does, it is best to look at the source code...
+- **Relatively high disk space usage**: To ensure that the system can be rolled back at any time, Nix preserves all historical environments by default, which can take up a lot of disk space. It can be a problem especially on some resource-constrained Virtual Machines.
+- **Error messages may be obscure**: Sometimes you may come across some strange error messages and don't understand what's going on. 
+`--show- Trace` may throw you a stack of errors that are of little help.
+
+
+### Summary
+
+Generally speaking, I think NixOS is suitable for developers who have some experience in using Linux and programming and want to have more control over their systems.
+
+I don't recommend you getting started with NixOS if you are new to Linux, it can be a very painful journey.

docs/introduction/index.md

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+---
+footer: false
+---
+
+## Introduction to Nix & NixOS
+
+Nix package manager is a declarative configuration management tool. Users need to declare the expected system state in some configuration, and Nix is responsible for achieving that goal.
+
+> To put it simply, "declarative configuration" means that users only need to declare the result they want. For example, you declare that you want to replace the i3 window manager with sway, then Nix will help you achieve the goal. You don't need to worry about the underlying details (such as which packages sway needs to install, which i3-related packages need to be uninstalled, which system configuration or environment variables need to be adjusted for sway, what adjustments need to be made to the Sway parameters if an Nvidia graphics card is used, etc.), Nix will automatically handle these details for the user(prerequisite: if the nix packages related to sway & i3 are designed properly.).
+
+NixOS, the Linux distribution built on top of the Nix package manager, can be simply described as "OS as Code", which describes the entire operating system's state using declarative Nix configuration files.
+
+An operating system has a variety of software packages, configuration files, text/binary data, which are all the current state of the system, and declarative configuration can manage only the static part of it.
+Those dynamic data (such as PostgreSQL/MySQL/MongoDB data) are obviously not manageable through a declarative configuration (you can't just delete all new postgresql data that is not declared in the configuration at every deployment).
+Therefore, **NixOS actually only supports to manage part of the state of the system in a declarative way**, and all the dynamic data mentioned above, as well as all the contents in the user's home directory, are not controlled by it (so when you rollback your NixOS to the last generation, NixOS will do nothing on these content).
+
+Although we cannot make the entire system reproducible, the `/home` directory, as an important user directory, does have many necessary configuration files.
+Another important community project, [home-manager](https://github.com/nix-community/home-manager), filled this gap.
+home-manager is designed to manage user-level packages & HOME directories.
+
+Due to Nix's features such as declarative and reproducible, Nix is not only used to manage desktop environments but also widely used to manage development environments, compilation environments, cloud virtual machines, container image construction, etc. [NixOps](https://github.com/NixOS/nixops) from the Nix official and [deploy-rs](https://github.com/serokell/deploy-rs) from the community are both operations tools based on Nix.
+
+
+## Why NixOS?
+
+I heard about the Nix package manager several years ago. It uses the Nix language to describe system configuration, and the Linux distribution built on top of it, can roll back the system to any historical state at any time(In fact, only the state declared by nix configuration files can be rollback). Although it sounds impressive, it requires learning a new language and writing code to install packages, I thought it was too troublesome and didn't study it at the time.
+
+But I recently encountered a lot of environmental problems in the process of using EndeavourOS, and I spent a lot of energy to solve them, which made me exhausted. After thinking about it carefully, I realized that the root cause was that EndeavourOS do not have any version control and rollback mechanism, which caused the system to be unable to be restored when problems occurred.
+
+So I switched to NixOS.
+
+I am quite satisfied with NixOS, even more than expected. 
+The most amazing thing is, now I can restore the entire i3 environment and my commonly used softwares on a fresh NixOS host with just one command, that's really fantastic!
+
+The rollback capability of NixOS gave me a lot of confidence - I no longer fear breaking the system any more. I even tried a lot of new things on NixOS, such as hyprland compositor. (On EndeavourOS before, I wouldn't have dared to play with such new compositors - it would have been a big hassle if something went wrong with the system and I need to fix it manually through various tricks.)
+
+So that's why I chose NixOS.

docs/introduction/installation.md

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+
+Nix can be installed in multiple ways:
+
+1. Install on macOS/Linux/WSL as a package manager.
+2. Install NixOS, it's a Linux distribution that uses Nix to manage the entire system environment.
+
+I chose to directly install NixOS using its official ISO image, to manage the entire system through Nix as much as possible.
+
+The installation process is simple, and I won't go into details here.
+
+Some materials that may be useful:
+
+1. [Official installation method of Nix](https://nixos.org/download.html): written in bash script, `nix-command` & `flakes` are still experimental features as of 2023-04-23, and need to be manually enabled.
+   1. You need to refer to the instructions in [Enable flakes - NixOS Wiki](https://nixos.wiki/wiki/Flakes) to enable `nix-command` & `flakes`.
+   2. The official installer does not provide any uninstallation method. To uninstall Nix on Linux/macOS, you need to manually delete all related files, users, and groups.
+2. [The Determinate Nix Installer](https://github.com/DeterminateSystems/nix-installer): a third-party installer written in Rust, which enables `nix-command` & `flakes` by default and provides an uninstallation command.