# Configuration for the Name Service Switch (/etc/nsswitch.conf). { config, lib, pkgs, ... }: with lib; let # only with nscd up and running we can load NSS modules that are not integrated in NSS canLoadExternalModules = config.services.nscd.enable; myhostname = canLoadExternalModules; mymachines = canLoadExternalModules; nssmdns = canLoadExternalModules && config.services.avahi.nssmdns; nsswins = canLoadExternalModules && config.services.samba.nsswins; ldap = canLoadExternalModules && (config.users.ldap.enable && config.users.ldap.nsswitch); sssd = canLoadExternalModules && config.services.sssd.enable; resolved = canLoadExternalModules && config.services.resolved.enable; hostArray = [ "files" ] ++ optionals mymachines [ "mymachines" ] ++ optionals nssmdns [ "mdns_minimal [!UNAVAIL=return]" ] ++ optionals nsswins [ "wins" ] ++ optionals resolved ["resolve [!UNAVAIL=return]"] ++ [ "dns" ] ++ optionals nssmdns [ "mdns" ] ++ optionals myhostname ["myhostname" ]; passwdArray = [ "files" ] ++ optional sssd "sss" ++ optionals ldap [ "ldap" ] ++ optionals mymachines [ "mymachines" ]; shadowArray = [ "files" ] ++ optional sssd "sss" ++ optionals ldap [ "ldap" ]; servicesArray = [ "files" ] ++ optional sssd "sss"; in { options = { # NSS modules. Hacky! # Only works with nscd! system.nssModules = mkOption { type = types.listOf types.path; internal = true; default = []; description = '' Search path for NSS (Name Service Switch) modules. This allows several DNS resolution methods to be specified via /etc/nsswitch.conf. ''; apply = list: { inherit list; path = makeLibraryPath list; }; }; }; config = { assertions = [ { # generic catch if the NixOS module adding to nssModules does not prevent it with specific message. assertion = config.system.nssModules.path != "" -> canLoadExternalModules; message = "Loading NSS modules from path ${config.system.nssModules.path} requires nscd being enabled."; } { # resolved does not need to add to nssModules, therefore needs an extra assertion assertion = resolved -> canLoadExternalModules; message = "Loading systemd-resolved's nss-resolve NSS module requires nscd being enabled."; } ]; # Name Service Switch configuration file. Required by the C # library. !!! Factor out the mdns stuff. The avahi module # should define an option used by this module. environment.etc."nsswitch.conf".text = '' passwd: ${concatStringsSep " " passwdArray} group: ${concatStringsSep " " passwdArray} shadow: ${concatStringsSep " " shadowArray} hosts: ${concatStringsSep " " hostArray} networks: files ethers: files services: ${concatStringsSep " " servicesArray} protocols: files rpc: files ''; # Systemd provides nss-myhostname to ensure that our hostname # always resolves to a valid IP address. It returns all locally # configured IP addresses, or ::1 and 127.0.0.2 as # fallbacks. Systemd also provides nss-mymachines to return IP # addresses of local containers. system.nssModules = optionals canLoadExternalModules [ config.systemd.package.out ]; }; }