this derivation will be built:
  /nix/store/m8hmv4b0lsdq48pi1jq83xvx3bhcxz2n-udev-custom-callback-0.3.drv
this path will be fetched (0.0 KiB download, 6.3 KiB unpacked):
  /nix/store/mkxbbww5bcwi0hhy9ndcncgqpj07800i-shadow-4.20.3-dev