
This option was removed because allowing (multiple) regular users to override host entries affecting the whole system opens up a huge attack vector. There seem to be very rare cases where this might be useful. Consider setting system-wide host entries using networking.hosts, provide them via the DNS server in your network, or use networking.networkmanager.appendNameservers to point your system to another (local) nameserver to set those entries.
*** NixOS *** NixOS is a Linux distribution based on the purely functional package management system Nix. More information can be found at http://nixos.org/nixos and in the manual in doc/manual.