Nix (package manager)/ja
Fundamental concepts
Tools and applications
Nixは、Nix Expression Language で表現された再現可能なビルド命令を解析するパッケージマネージャーおよびビルドシステムであり、これは遅延評価を伴う純粋関数型言語である。Nix expressions は、依存関係を引数として取り、パッケージに対して再現可能なビルド環境derivationを作成する純粋関数[1]です。Nixは、ビルドの結果を完全な依存関係ツリーのハッシュで指定された一意のアドレスに保存し、不変のパッケージストアを作成することで、原子的な更新、ロールバックを実現する。また、異なるバージョンのパッケージを同時にインストールすることで、根本的に依存関係地獄を防ぐ。
使い方
インストール
NixOSでは、Nix は最初からインストールされている。
他の Linux ディストリビューションや macOS 上では、installation section of the Nix manualに従ってインストールできる。
Nix コマンド
Nix コマンドは、Nix リファレンスマニュアルに、主なコマンド、ユーティリティ、および実験コマンドが文書化されている。バージョン2.0(2018年2月リリース)以前は、さまざまなコマンドが存在していた。
設定
NixOS 上では、nix optionを用いてNixで設定することができる。
Standalone Nix is configured through nix.conf (usually found in /etc/nix/). Details on the available options are found in the Nix reference manual.
You can also configure Nix using Home Manager, which manages declarative environments for a single user. For system-wide configuration, you can use System Manager on Linux and nix-darwin on macOS.
Internals
Nix store
Packages built by Nix are placed in the read-only Nix store, normally found in /nix/store. Each package is given a unique address specified by a cryptographic hash followed by the package name and version, for example /nix/store/nawl092prjblbhvv16kxxbk6j9gkgcqm-git-2.14.1. These prefixes hash all the inputs to the build process, including the source files, the full dependency tree, compiler flags, etc. This allows Nix to simultaneously install different versions of the same package, and even different builds of the same version, for example variants built with different compilers. When adding, removing or updating a package, nothing is removed from the store; instead, symlinks to these packages are added, removed or changed in profiles.
Cleaning the Nix store
For information relating to cleaning the Nix store, refer to NixOS Manual: Chapter - Cleaning the Nix Store.
Nix store corruption
For information relating to fixing a corrupted Nix store, refer to NixOS Manual: Chapter - Nix Store Corruption.
Valid Nix store names
- Main article: Valid Nix store path names
Profiles
In order to construct a coherent user or system environment, Nix symlinks entries of the Nix store into profiles. These are the front-end by which Nix allows rollbacks: since the store is immutable and previous versions of profiles are kept, reverting to an earlier state is simply a matter of change the symlink to a previous profile. To be more precise, Nix symlinks binaries into entries of the Nix store representing the user environments. These user environments are then symlinked into labeled profiles stored in /nix/var/nix/profiles, which are in turn symlinked to the user's ~/.nix-profile.
Sandboxing
When sandbox builds are enabled, Nix will setup an isolated environment for each build process. It is used to remove further hidden dependencies set by the build environment to improve reproducibility. This includes access to the network during the build outside of fetch* functions and files outside the Nix store. Depending on the operating system access to other resources are blocked as well (ex. inter process communication is isolated on Linux).
Sandboxing is enabled by default on Linux, and disabled by default on macOS.
In pull requests for Nixpkgs people are asked to test builds with sandboxing enabled (see Tested using sandboxing in the pull request template) because in official Hydra builds sandboxing is also used.
To configure Nix for sandboxing, set sandbox = true in /etc/nix/nix.conf; to configure NixOS for sandboxing set nix.useSandbox = true; in configuration.nix. The nix.useSandbox option is true by default since NixOS 17.09.
Alternative Interpreters
There is an ongoing effort to reimplement Nix, from the ground up, in Rust.
There is also a community-led fork of Nix 2.18 named Lix, focused on correctness, usability, and growth. While it has also ported some components of Nix to Rust, it is not a ground-up rewrite like Tvix.
Earlier attempts can be found on riir-nix
Notes
- ↑ 変数は不変で、引数が変化しない場合、関数は常に同じ値を返す。