NixOS Offline ISO Builder

This repository provides a flake template for creating offline ISO images of the NixOS Calamares installer with Gnome.

It patches over v0.3.14 of the Calamares NixOS Extensions to disable checking for an online connection, and modifies the Nixos install module script to install user provided configuration files.

Usage

• Install Nix or NixOS to your online build system and enable flake support
• Clone this repo to a directory where you wish to build your ISO
• Copy your configuration files to the ./nix-cfg directory
• You will need to have a hardware-configuration.nix template file in this directory with your configuraiton.nix file
• The hardware-configuration.nix will be over-written by the installation process, but it is needed to build the configuration for the ISO
• Include the build dependencies directive in either your configuration.nix or the ISO's flake.nix
• Build the ISO with:

nix build .#iso.offline-installer-x86_64-linux

• Use dd or other imaging software to write your ISO image to disk
• Boot your target system from the installation medium and start the install process as normal
• Ensure you configure the same desktop environment and user as in your configuration
• The install may take a very long time (and appear stuck on 46%) this is because of the dependencies being copied. Toggle the log to view activity

Build Dependencies

You must include system build dependencies in one of two ways:

1. In your configuration.nix file by declaring -

  system.includeBuildDependencies = true;

This will include all the system dependencies as part of the configuration and will allow you to both install from the ISO image and re-build your system configuration while offline (provided you don't add any dependencies). For more information on this option, see Linus Heckemann's blog

2. In the ISO's flake.nix file by declaring -

            isoImage = {
              contents = [
                {
                    source = ./nix-cfg;
                    target = "/nix-cfg";
                }
              ];
              storeContents = [ 
                config.system.build.toplevel
              ];
              includeSystemBuildDependencies = true;
            }

If you do not include dependencies in your configuration.nix, then they must be declared here so they are included in the nix store for the ISO. However, they will not be installed to the system as part of the installation process. This will result in a much smaller nix store on your target system, but you will not be able to re-build its configuration offline.

Free Disk Space

Ensure your nix store partition has enough free space to build the ISO. The ISO will be much larger than normal (20+ Gb) depending on what dependencies are included. I recommend having at least 3x the ISO size available, or approx. 100+ Gb free.

Modules

The installation script will recursively copy configuration files from either /iso/nix-cfg or /tmp/nix-cfg to /etc/nixos on the target system. This allows you to use any number of files and sub-directories for your configuration.

Dynamic Configuration

• The installer will look for user configuration files in /tmp/nix-cfg prior to searching /iso/nix-cfg. This allows you to dynamically change the system configuration after booting into the installation environment
• If configuration changes add dependencies, then the install will fail because they will be missing from the ISO's nix store

Install Options

• You must choose the same Desktop environment as your configuration.nix specifies otherwise the install will fail with missing dependencies
• You must create the same user as your configuration.nix specifies, otherswise the installer will fail to set the password for your user

Limitations

Flake configurations are not supported. I have not found a way to make a flake based system configuration work completely offline. There are also open issues related to this problem. If anyone has a solution, I would be very interested in seeing it.