Analysis of the NixOS Flake Installer Script

This document breaks down the installer shell script into plain, easy-to-understand terms. The script is designed to automate either a fresh NixOS installation from a Live ISO or update an existing NixOS system using Nix Flakes.

1. Core Functions of the Script

The script performs three primary tasks: 1. Detects the Environment: It checks whether you are running it from a temporary Live ISO (to install NixOS) or from an already installed NixOS system (to update it). 2. Collects User Preferences: It prompts you for basic system settings (username, hostname, password, and graphics driver). 3. Executes Setup/Updates: * For New Installs: It formats your storage, installs NixOS, sets up user profiles, and configures the hardware. * For Existing Systems: It safely cleans up old configurations, updates hardware detection files, and rebuilds the system.

2. Step-by-Step Code Execution Flow

The script runs in the following sequence:

Step 1: Environment Check and Tool Loading

  • The script checks if /iso exists or if the root system is loaded in temporary memory (tmpfs).
  • If on a Live ISO: It automatically downloads and opens a temporary shell containing git, pciutils (for hardware checking), and disko (for partition management) so the installer has all required tools.
  • Privilege Check:
    • If on a Live ISO, the script insists on being run as root (sudo).
    • If on an already installed system, it insists on being run as a normal user to avoid configuration ownership issues.

Step 2: System Configuration Prompts

The script asks you for: * Username: The name of your user account (defaulting to your current user). * Hostname: The network name for your computer (defaulting to nixos). * Password: Securely prompts you to type and confirm a password. * GPU Driver: Prompts you to select your graphics card manufacturer: Nvidia, AMD, or Intel.

Step 3: Deployment Route Selection

The script splits into two different pathways depending on its environment check:

PATH A: Fresh Installation (Live ISO Mode)

WARNING: Partitioning disks and formatting drives will permanently destroy existing data. Ensure you have backed up any crucial files before proceeding.

You are given three disk options:

  1. Option 1 (Automated Wipe): Uses the disko tool to completely wipe and format an entire selected drive (e.g., sda or nvme0n1).
  2. Option 2 (Custom Partitions): Allows you to choose pre-existing system partitions manually. It formats the EFI partition to vfat and the root partition to Btrfs, creating the subvolumes @, @home, and @nix.
  3. Option 3 (Personal Quick-Default): Automatically wipes and formats /dev/sda1 and /dev/sda2 using default disko templates.

Once partitioning is complete, the script: * Copies your NixOS configuration files to /mnt/etc/nixos. * Generates a clean hardware configuration file, deliberately ignoring sensitive mount paths like secrets or rclone. * Swaps your chosen username and graphics driver into the variables configuration file. * Runs nixos-install to build and install the operating system. * Sets your user password on the newly installed system. * Creates default directories (Downloads, Documents, etc.) in your home folder and copies your NixOS configuration files there for future edits.

PATH B: Existing System Upgrade Mode

If the script is run on an already functioning NixOS system, it: * Updates your username and graphics driver choices in the local variables file. * Deletes old, conflicting profile files for Firefox, Zen Browser, GTK configurations, and Cava to prevent configuration conflicts. * Reads your current machine’s physical hardware structure and writes a clean hardware file to hosts/default/hardware-configuration.nix. * Stage-adds this hardware file to your local Git directory. * Runs sudo nixos-rebuild switch --flake .#default to rebuild and apply your updated configuration.

3. Post-Installation Note

At the end of either pathway, a yellow warning banner appears reminding you that: * Encrypted secrets config files (sops, git config) have been skipped. * Git signing keys and cloud storage connections (rclone) were not configured automatically. * You must set these up manually after logging in.