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.
If you want CUPS to receive UDP printer announcements from the rest of the
world, please add
networking.firewall.allowedUDPPorts = [ 631 ];
to /etc/nixos/configuration.nix.
See <http://lists.science.uu.nl/pipermail/nix-dev/2013-November/011997.html>
for the discussion that lead to this.
That is, you can say
security.pam.services.sshd = { options... };
instead of
security.pam.services = [ { name = "sshd"; options... } ];
making it easier to override PAM settings from other modules.
