Migrating NixOS configuration to Flakes

"Make your configuration ‘modern and portable’." This guide walks you through migrating from a traditional /etc/nixos/configuration.nix to Flakes.

Step 1: Create a project directory#

Create a dedicated configuration directory (such as ~/nixos-config). Do not make ad hoc changes directly inside /etc/nixos.

mkdir ~/nixos-config
cd ~/nixos-config
# 复制原有的硬件配置
cp /etc/nixos/hardware-configuration.nix .
# 复制原有的系统配置
cp /etc/nixos/configuration.nix .

Step 2: Write flake.nix#

Create flake.nix in the project root.

{
  description = "我的 2026 版 NixOS 配置";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
  };

  outputs = { self, nixpkgs, ... }@inputs: {
    nixosConfigurations.my-host = nixpkgs.lib.nixosSystem {
      system = "x86_64-linux";
      # 传递参数给子模块
      specialArgs = { inherit inputs; };
      modules = [
        ./configuration.nix
      ];
    };
  };
}

Step 3: Adjust configuration.nix#

Because the Flake uses nixpkgs.lib.nixosSystem, you may need to adjust the top-level arguments in your existing configuration.nix:

# 修改前：
# { config, pkgs, ... }:

# 修改后：
{ config, pkgs, inputs, ... }: {
  imports = [
    ./hardware-configuration.nix
  ];

  # 启用 Flakes 和新的 Nix CLI
  nix.settings.experimental-features = [ "nix-command" "flakes" ];

  # 其他配置项...
  system.stateVersion = "24.11"; # 示例初装版本；迁移时保留原值
}

Step 4: Build and apply#

Note: In Flake mode, when a Flake is read from a local Git working tree, the files it references must be tracked by Git (you can git add new files first). Explicit path: sources behave differently. Inspect the staged contents first to avoid including private keys or unrelated files.

git init
git add flake.nix configuration.nix hardware-configuration.nix
nix flake check --no-build
nixos-rebuild dry-build --flake .#my-host
nixos-rebuild build --flake .#my-host
# 检查构建结果、恢复路径与变更后，手动激活：
sudo nixos-rebuild switch --flake .#my-host

• .: Refers to the current directory.
• #my-host: Matches the name defined in outputs.nixosConfigurations.

Benefits of migrating#

• No dependence on a global Channel: The system version is determined entirely by flake.lock.
• Easy to back up: Simply push this directory to GitHub.
• Modular configuration: You can easily split the configuration into files such as desktop.nix and user.nix, then reference them in configuration.nix under imports.

Checks after activation#

A successful build proves only that the build stage works. After activation, check the current system generation, service status, and desktop behavior before proceeding with Home Manager integration.