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feat: flakes & the New CLI
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Ryan Yin
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@ -9,7 +9,7 @@ In simple terms, if you've worked with some JavaScript/Go/Rust/Python, you shoul
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Similarly, the package managers in these programming languages also use files like `package-lock.json`/`go.sum`/`Cargo.lock`/`poetry.lock` to lock the versions of dependencies, ensuring the reproducibility of projects.
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Flakes borrow ideas from these package managers to enhance the reproducibility, composability, and usability of the Nix ecosystem.
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Flakes introduce `flake.nix`, similar to `package.json`, to describe the dependencies between Nix packages and how to build projects.
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Flakes introduce `flake.nix`, similar to `package.json`, to describe the dependencies between Nix packages and how to build projects.
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Additionally, it provides `flake.lock`, akin to `package-lock.json`, to lock the versions of dependencies, ensuring project reproducibility.
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## A Word of Caution about Flakes <Badge type="danger" text="caution" />
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@ -20,30 +20,6 @@ The benefits of Flakes are evident, and the entire NixOS community has embraced
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Overall, I strongly recommend everyone to use Flakes, especially since this book revolves around NixOS and Flakes. However, it's crucial to be prepared for potential problems that may arise due to forthcoming breaking changes.
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## Nix Flakes and Classic Nix
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> Currently the New CLI is strongly bound to the Flakes feature(although there is aleardy a clear plan to split them now), so I will use the term "Flakes" to refer to the New CLI & Flakes feature in this book.
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Since the `nix-command` and `flakes` features are still experimental, the official documentation lacks detailed coverage, and the community's documentation on them is also scattered. From the perspective of reproducibility, ease of management, and maintenance, the classic Nix package structure and CLI are no longer recommended. Therefore, I will not delve into the usage of classic Nix. Beginners are advised to start with `nix-command` and `flakes` while disregarding any content related to classic Nix.
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The following are classic Nix commands and associated concepts that are no longer necessary after enabling `nix-command` and `flakes`. When searching for information, you can safely ignore them:
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1. `nix-channel`: `nix-channel` manages software package versions through stable/unstable/test channels, similar to other package management tools such as apt/yum/pacman.
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1. In Flakes, the functionality of `nix-channel` is entirely replaced by the `inputs` section in `flake.nix`.
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2. `nix-env`: `nix-env` is a core command-line tool for classic Nix used to manage software packages in the user environment.
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1. It installs packages from the data sources added by `nix-channel`, causing the installed package's version to be influenced by the channel. Packages installed with `nix-env` are not automatically recorded in Nix's declarative configuration and are completely independent of its control, making them challenging to reproduce on other machines. Therefore, it is not recommended to use this tool.
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2. The corresponding command in Flakes is `nix profile`. Personally, I don't recommend it for beginners either.
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3. `nix-shell`: `nix-shell` creates a temporary shell environment, which is useful for development and testing.
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1. In Flakes, this tool is divided into three sub-commands: `nix develop`, `nix shell`, and `nix run`. We will discuss these three commands in detail in the "[Development](../development/intro.md)" chapter.
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4. `nix-build`: `nix-build` builds Nix packages and places the build results in `/nix/store`, but it does not record them in Nix's declarative configuration.
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1. In Flakes, `nix-build` is replaced by `nix build`.
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5. `nix-collect-garbage`: Garbage collection command used to clean up unused Store Objects in `/nix/store`.
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1. There is a smimilar command in Flakes, `nix store gc`, but it do not clean the profile generations.
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6. And other less commonly used commands are not listed here.
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1. You can refer to the detailed command comparison list in [Try to explain nix commands](https://qiita.com/Sumi-Sumi/items/6de9ee7aab10bc0dbead?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en).
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> NOTE: `nix-env -qa` may still be useful in some cases, as it returns all packages installed in the system.
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## Flakes Tutorials
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I won't go into too much detail here, please refer to the following documents:
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@ -64,7 +40,34 @@ I delved into some details regarding Flakes:
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- [ teaching Nix 3 CLI and Flakes #281 - nix.dev](https://github.com/NixOS/nix.dev/issues/281): An issue about "Teaching Nix 3 CLI and Flakes" in nix.dev, and the conclusion is that we should not promote unstable features in nix.dev.
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- [Draft: 1-year Roadmap - NixOS Foundation](https://nixos-foundation.notion.site/1-year-roadmap-0dc5c2ec265a477ea65c549cd5e568a9): A roadmap provided by the NixOS Foundation, which includes plans regarding the stabilization of Flakes.
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After reviewing these resources, it seems likely that Flakes will be stabilized within one or two years, possibly accompanied by some breaking changes.
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After reviewing these resources, it seems that Flakes may be(or may not...) stabilized within two years, possibly accompanied by some breaking changes.
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## the New CLI and the Classic CLI
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Nix introduced two experimental features, `nix-command` and `flakes`, in the year 2020.
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These features bring forth a new command-line interface (referred to as the New CLI), a standardized Nix package structure definition (known as the Flakes feature), and features like `flake.lock`, similar to version lock files in cargo/npm.
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Despite being experimental as of February 1, 2024, these features have gained widespread adoption within the Nix community due to their significant enhancement of Nix capabilities.
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The current Nix New CLI (the `nix-command` experimental feature) is tightly coupled with the Flakes experimental feature.
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While there are ongoing efforts to explicitly separate them, using Flakes essentially requires the use of the New CLI.
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In this book, serving as a beginner's guide to NixOS and Flakes, it is necessary to introduce the differences between the New CLI, which Flakes relies on, and the old CLI.
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Here, we list the old Nix CLI and related concepts that are no longer needed when using the New CLI and Flakes (`nix-command` and `flakes`).
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When researching, you can replace them with the corresponding New CLI commands (except for `nix-collect-garbage`, as there is currently no alternative for this command):
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1. `nix-channel`: `nix-channel` manages software package versions through stable/unstable/test channels, similar to other package management tools such as apt/yum/pacman.
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1. In Flakes, The functionality of `nix-channel` is entirely replaced by the `inputs` section in `flake.nix`.
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2. `nix-env`: `nix-env` is a core command-line tool for classic Nix used to manage software packages in the user environment.
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1. It installs packages from the data sources added by `nix-channel`, causing the installed package's version to be influenced by the channel. Packages installed with `nix-env` are not automatically recorded in Nix's declarative configuration and are completely independent of its control, making them challenging to reproduce on other machines. Therefore, it is not recommended to use this command directly.
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2. The corresponding command in the New CLI is `nix profile`. Personally, I don't recommend it for beginners.
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3. `nix-shell`: `nix-shell` creates a temporary shell environment, which is useful for development and testing.
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1. New CLI: This tool is divided into three sub-commands: `nix develop`, `nix shell`, and `nix run`. We will discuss these three commands in detail in the "[Development](../development/intro.md)" chapter.
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4. `nix-build`: `nix-build` builds Nix packages and places the build results in `/nix/store`, but it does not record them in Nix's declarative configuration.
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1. New CLI: `nix-build` is replaced by `nix build`.
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5. `nix-collect-garbage`: Garbage collection command used to clean up unused Store Objects in `/nix/store`.
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1. There is a smimilar command in the New CLI, `nix store gc --debug`, but it do not clean the profile generations, so there is currently no alternative for this command.
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6. And other less commonly used commands are not listed here.
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1. You can refer to the detailed command comparison list in [Try to explain nix commands](https://qiita.com/Sumi-Sumi/items/6de9ee7aab10bc0dbead?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en).
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[^1]: [Flakes - NixOS Wiki](https://nixos.wiki/index.php?title=Flakes)
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[^2]: [Flakes are such an obviously good thing](https://grahamc.com/blog/flakes-are-an-obviously-good-thing/)
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@ -22,34 +22,6 @@ Flakes 带来的好处是显而易见的，整个 NixOS 社区都很喜欢它，
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总的来说，我仍然推荐大家使用 Flakes，毕竟这本书本身也是围绕 NixOS 与 Flakes 编写的，但是也要做好准备——未来可能需要解决一些不兼容变更带来的问题。
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## Flakes 与传统的 Nix
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> 当前 New CLI 与 Flakes 特性是强绑定的（虽然现在已经有明确的拆分计划），因此在本书中我会使用 Flakes 来指代 New CLI 与 Flakes 两项特性。
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Nix 于 2020 年推出了 `nix-command` & `flakes` 两个新特性，它们提供了全新的命令行工具、标准的 Nix 包结构定义、类似 cargo/npm 的 `flake.lock` 版本锁文件等等。这两个特性极大地增强了 Nix 的能力，因此虽然至今（2023/5/5）它们仍然是实验性特性，但是已经被 Nix 社区广泛使用。
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但由于 `nix-command` & `flakes` 仍然是实验性特性，官方文档基本不包含任何介绍它们的内容，同时社区关于 Flakes 的文档也相当分散且不完整。
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但是从可复现、易于管理维护的角度讲，旧的 Nix 包结构与命令行工具已经不推荐使用了，因此本书也不会介绍旧的 Nix 包结构与命令行工具的使用方法，也建议新手直接忽略掉这些旧的内容，从 `nix-command` & `flakes` 学起。
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这里列举下在 `nix-command` & `flakes` 中已经不需要用到的旧的 Nix 命令行工具与相关概念，在查找资料时，如果看到它们直接忽略掉就行：
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1. `nix-channel`: 与 apt/yum/pacman 等其他 Linux 发行版的包管理工具类似，传统的 Nix 也以 stable/unstable/test 等 channel 的形式来管理软件包的版本，可通过此命令修改 Nix 的 channel 信息。
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1. Nix Flakes 在 `flake.nix` 中通过 `inputs` 声明依赖包的数据源，通过 `flake.lock` 锁定依赖版本，完全取代掉了 `nix-channel` 的功能。
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2. `nix-env`: 用于管理用户环境的软件包，是传统 Nix 的核心命令行工具。它从 `nix-channel` 定义的数据源中安装软件包，所以安装的软件包版本受 channel 影响。
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1. 通过 `nix-env` 安装的包不会被自动记录到 Nix 的声明式配置中，是完全脱离掌控的，无法在其他主机上复现，因此不推荐使用。
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2. 在 Nix Flakes 中对应的命令为 `nix profile`，我个人也不太推荐初学者尝试它.
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3. `nix-shell`: nix-shell 用于创建一个临时的 shell 环境
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1. 这玩意儿可能有点复杂了，因此在 Nix Flakes 中它被拆分成了三个子命令 `nix develop`, `nix shell` 以及 `nix run`，我们会在「[构建开发环境](../development/intro.md)」一章详细介绍这三个命令。
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4. `nix-build`: 用于构建 Nix 包，它会将构建结果放到 `/nix/store` 路径下，但是不会记录到 Nix 的声明式配置中。
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1. 在 Nix Flakes 中对应的命令为 `nix build`
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5. `nix-collect-garbage`: 垃圾回收指令，用于清理 `/nix/store` 中未被使用的 Store Objects.
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1. 在 Nix Flakes 中有个相似的指令 `nix store gc --debug`，但它不会清理 profile 生成的历史版本，因此此命令暂无替代。
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6. 以及其他使用地较少的命令，就不一一列出了.
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1. 详细的命令对比列表可以看看 [Try to explain nix commands](https://qiita-com.translate.goog/Sumi-Sumi/items/6de9ee7aab10bc0dbead?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en)
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> 可能也就 `nix-env -qa` 这个命令偶尔还会有些用了，它返回当前系统下安装的所有软件包。
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## Flakes 入门
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我就不多介绍了，请直接参考如下文档：
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@ -70,7 +42,33 @@ Nix 于 2020 年推出了 `nix-command` & `flakes` 两个新特性，它们提
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- [ teaching Nix 3 CLI and Flakes #281 - nix.dev](https://github.com/NixOS/nix.dev/issues/281): 社区关于是否应该在 NixOS 官方文档中介绍 Flakes 的讨论，当前结论是官方文档不应该推广使用 unstable 功能。
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- [Draft: 1 year roadmap - NixOS Foundation](https://nixos-foundation.notion.site/1-year-roadmap-0dc5c2ec265a477ea65c549cd5e568a9): NixOS Fundation 的一份 Roadmap，其中提到了 Flakes 的计划：`Stabilize flakes and release Nix 3.0. Flakes are widely used (there are more GitHub repos being created with a flake.nix than a default.nix) but they’re still marked as experimental, which is not a good situation. The same applies to the new nix CLI.`
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读完上述内容后，个人猜测，**Flakes 可能会在未来一两年内成为稳定特性**。
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读完上述内容后，个人猜测，**Flakes 有可能（仅是可能）会在未来两年内成为稳定特性**。
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## Nix 的新 CLI 与旧的 CLI {#the-new-cli-and-the-classic-cli}
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Nix 于 2020 年推出了 `nix-command` & `flakes` 两个实验特性，它们提供了全新的命令行工具（即 New CLI）、标准的 Nix 包结构定义（即 Flakes 特性）、类似 cargo/npm 的 `flake.lock` 版本锁文件等等。这两个特性极大地增强了 Nix 的能力，因此虽然至今（2024/2/1）它们仍然是实验性特性，但是已经被 Nix 社区广泛使用。
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当前 Nix 的 New CLI（即 `nix-command` 实验特性） 与 Flakes 实验特性是强绑定的关系，虽然现在已经有明确的拆分计划正在推进中了，但要用 Flakes 基本上就必须得用 New CLI.
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而本书作为一本 NixOS & Flakes 新手指南，就有必要介绍下 Flakes 实验特性所依赖的 New CLI 与旧的 CLI 的区别。
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这里列举下在启用了 New CLI 与 Flakes(`nix-command` & `flakes`) 实验特性后，已经不需要用到的旧的 Nix 命令行工具与相关概念。
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在查找资料时，如果看到它们直接忽略掉就行（`nix-collect-garbage` 除外，该命令目前暂无替代）：
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1. `nix-channel`: 与 apt/yum/pacman 等其他 Linux 发行版的包管理工具类似，传统的 Nix 也以 stable/unstable/test 等 channel 的形式来管理软件包的版本，可通过此命令修改 Nix 的 channel 信息。
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1. Nix Flakes 在 `flake.nix` 中通过 `inputs` 声明依赖包的数据源，通过 `flake.lock` 锁定依赖版本，完全取代掉了 `nix-channel` 的功能。
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2. `nix-env`: 用于管理用户环境的软件包，是传统 Nix 的核心命令行工具。它从 `nix-channel` 定义的数据源中安装软件包，所以安装的软件包版本受 channel 影响。
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1. 通过 `nix-env` 安装的包不会被自动记录到 Nix 的声明式配置中，是完全脱离掌控的，无法在其他主机上复现，因此不推荐使用。
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2. New CLI 中对应的命令为 `nix profile`，我个人不太推荐初学者直接尝试它.
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3. `nix-shell`: nix-shell 用于创建一个临时的 shell 环境
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1. 这玩意儿可能有点复杂了，因此在 New CLI 中它被拆分成了三个子命令 `nix develop`, `nix shell` 以及 `nix run`，我们会在「[构建开发环境](../development/intro.md)」一章详细介绍这三个命令。
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4. `nix-build`: 用于构建 Nix 包，它会将构建结果放到 `/nix/store` 路径下，但是不会记录到 Nix 的声明式配置中。
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1. 在 New CLI 中对应的命令为 `nix build`
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5. `nix-collect-garbage`: 垃圾回收指令，用于清理 `/nix/store` 中未被使用的 Store Objects.
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1. 在 New CLI 中有个相似的指令 `nix store gc --debug`，但它不会清理 profile 生成的历史版本，因此此命令暂无替代。
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6. 以及其他使用地较少的命令，就不一一列出了.
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1. 详细的命令对比列表可以看看 [Try to explain nix commands](https://qiita-com.translate.goog/Sumi-Sumi/items/6de9ee7aab10bc0dbead?_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en)
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[^1]: [Flakes - NixOS Wiki](https://nixos.wiki/index.php?title=Flakes)
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[^2]: [Flakes are such an obviously good thing](https://grahamc.com/blog/flakes-are-an-obviously-good-thing/)
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