NIXPKG1 http://nixos.org/releases/nixpkgs/nixpkgs-0.12/MANIFEST tcpdump-3.9.4 x86_64-linux /nix/store/7wl54m2psikysrck3k5q03347gxv9hvd-tcpdump-3.9.4.drv /nix/store/8xr182x6b0g57rs6slsj7l2q23fay5h7-tcpdump-3.9.4