nixpkgs/nixos/modules/installer/cd-dvd/channel.nix
Jörg Thalheim 94b810348a installer/cd-dvd/channel: allow to disable bundled channel
When building kexec-based installer every mb saved will reduce the RAM usage and allow to install NixOS on smaller machines.
It also means that less data has to be downloaded from the network.
When using flakes or niv we no longer rely on nix channels beeing present
and when using something like nixos-anywhere, we no longer need to evaluate anything in the installer at all.
2023-11-02 12:39:05 +01:00

65 lines
2.8 KiB
Nix

# Provide an initial copy of the NixOS channel so that the user
# doesn't need to run "nix-channel --update" first.
{ config, lib, pkgs, ... }:
let
# This is copied into the installer image, so it's important that it is filtered
# to avoid including a large .git directory.
# We also want the source name to be normalised to "source" to avoid depending on the
# location of nixpkgs.
# In the future we might want to expose the ISO image from the flake and use
# `self.outPath` directly instead.
nixpkgs = lib.cleanSource pkgs.path;
# We need a copy of the Nix expressions for Nixpkgs and NixOS on the
# CD. These are installed into the "nixos" channel of the root
# user, as expected by nixos-rebuild/nixos-install. FIXME: merge
# with make-channel.nix.
channelSources = pkgs.runCommand "nixos-${config.system.nixos.version}"
{ preferLocalBuild = true; }
''
mkdir -p $out
cp -prd ${nixpkgs.outPath} $out/nixos
chmod -R u+w $out/nixos
if [ ! -e $out/nixos/nixpkgs ]; then
ln -s . $out/nixos/nixpkgs
fi
${lib.optionalString (config.system.nixos.revision != null) ''
echo -n ${config.system.nixos.revision} > $out/nixos/.git-revision
''}
echo -n ${config.system.nixos.versionSuffix} > $out/nixos/.version-suffix
echo ${config.system.nixos.versionSuffix} | sed -e s/pre// > $out/nixos/svn-revision
'';
in
{
options.system.installer.channel.enable = (lib.mkEnableOption "bundling NixOS/Nixpkgs channel in the installer") // { default = true; };
config = lib.mkIf config.system.installer.channel.enable {
# Pin the nixpkgs flake in the installer to our cleaned up nixpkgs source.
# FIXME: this might be surprising and is really only needed for offline installations,
# see discussion in https://github.com/NixOS/nixpkgs/pull/204178#issuecomment-1336289021
nix.registry.nixpkgs.to = {
type = "path";
path = "${channelSources}/nixos";
};
# Provide the NixOS/Nixpkgs sources in /etc/nixos. This is required
# for nixos-install.
boot.postBootCommands = lib.mkAfter
''
if ! [ -e /var/lib/nixos/did-channel-init ]; then
echo "unpacking the NixOS/Nixpkgs sources..."
mkdir -p /nix/var/nix/profiles/per-user/root
${config.nix.package.out}/bin/nix-env -p /nix/var/nix/profiles/per-user/root/channels \
-i ${channelSources} --quiet --option build-use-substitutes false \
${lib.optionalString config.boot.initrd.systemd.enable "--option sandbox false"} # There's an issue with pivot_root
mkdir -m 0700 -p /root/.nix-defexpr
ln -s /nix/var/nix/profiles/per-user/root/channels /root/.nix-defexpr/channels
mkdir -m 0755 -p /var/lib/nixos
touch /var/lib/nixos/did-channel-init
fi
'';
};
}