
/dev/random is an exhaustible resource. Presumably, unbound will not be used to generate long-term encryption keys and so allowing it to use /dev/random only increases the risk of entropy exhaustion for no benefit.
*** 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.