https://nix.dev/tutorials/ad-hoc-developer-environments.html
https://nix.dev/tutorials/declarative-and-reproducible-developer-environments.html
    https://nix.dev/reference/pinning-nixpkgs.html
https://nix.dev/tutorials/towards-reproducibility-pinning-nixpkgs.html

https://nixos.org/guides/nix-pills/our-first-derivation.html
    ??? I remind you how to enter the Nix environment: source ~/.nix-profile/etc/profile.d/nix.sh 

2013
https://sandervanderburg.blogspot.com/2013/09/composing-fhs-compatible-chroot.html