My NixOS and Home Manager configurations.

Todo: add explanations of everything.

Useful notes for myself:

sudo nix-collect-garbage --delete-older-than 14d

Note on buildInputs vs nativeBuildInputs (which I always mix up):

• Think of cross compilation!
  • nativebuildInputs are native binaries for the build computer, i.e. build deps.
  • buildInputs may not be native to the build computer, i.e. runtime deps. In the case of native compilation (not cross), these both use the build computer's os/arch.
• Note that pkgs.callPackage secretly uses pkgs.buildPackages.X for things inside of nativeBuildInputs, which is why cross compilation is mostly invisible to the package.nix author :O (and why you should always callPackage so things get resolved properly)
• see https://jade.fyi/blog/flakes-arent-real/ cross compilation section

Notes on ln -s input $out vs cp input $out:

• if input resolves to a full store path, ln -s simply saves space and should be used.
• if you ln -s a single file from a 10gb store path into $out, now $out depends on the entire 10gb store path which cannot be gc'ed.
• if cp is used, the data is duplicated; this may be what you want (eg copying only some files from drv A to drv B saves space if A doesn't depend on B from anything else)
• see https://discourse.nixos.org/t/symlinking-vs-copying-into-out/11132

Note on manually stepping through the build process of a derivation:

• use nix develop nixpkgs#program in a new empty directory, but STAY IN BASH. For some reason when entering ZSH you lose certain things like genericBuild and runPhase.
• you can manually runPhase unpackPhase for every single phase (listed here: https://nixos.org/manual/nixpkgs/stable/#sec-stdenv-phases ), OR you can just run genericBuild

To see the difference / what changes between generations:

nix profile diff-closures --profile /nix/var/nix/profiles/system