This helps in setting a fixed firewall open port for NFS lockd.
Based on:
http://rlworkman.net/howtos/NFS_Firewall_HOWTO
(cherry picked from commit b32ca0616ff70795f71995fa79ea508b82f30b3a)
Conflicts:
nixos/modules/services/network-filesystems/nfsd.nix
Using pkgs.lib on the spine of module evaluation is problematic
because the pkgs argument depends on the result of module
evaluation. To prevent an infinite recursion, pkgs and some of the
modules are evaluated twice, which is inefficient. Using ‘with lib’
prevents this problem.