# 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; # XXX Move these to their respective modules nssmdns = canLoadExternalModules && config.services.avahi.nssmdns; nsswins = canLoadExternalModules && config.services.samba.nsswins; ldap = canLoadExternalModules && (config.users.ldap.enable && config.users.ldap.nsswitch); resolved = canLoadExternalModules && config.services.resolved.enable; googleOsLogin = canLoadExternalModules && config.security.googleOsLogin.enable; hostArray = mkMerge [ (mkBefore [ "files" ]) (mkIf mymachines [ "mymachines" ]) (mkIf nssmdns [ "mdns_minimal [NOTFOUND=return]" ]) (mkIf nsswins [ "wins" ]) (mkIf resolved [ "resolve [!UNAVAIL=return]" ]) (mkAfter [ "dns" ]) (mkIf nssmdns (mkOrder 1501 [ "mdns" ])) # 1501 to ensure it's after dns (mkIf myhostname (mkOrder 1600 [ "myhostname" ])) # 1600 to ensure it's always the last ]; passwdArray = mkMerge [ (mkBefore [ "files" ]) (mkIf ldap [ "ldap" ]) (mkIf mymachines [ "mymachines" ]) (mkIf googleOsLogin [ "cache_oslogin oslogin" ]) (mkIf canLoadExternalModules (mkAfter [ "systemd" ])) ]; shadowArray = mkMerge [ (mkBefore [ "files" ]) (mkIf ldap [ "ldap" ]) ]; 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; }; }; system.nssDatabases = { passwd = mkOption { type = types.listOf types.str; description = '' List of passwd entries to configure in /etc/nsswitch.conf. Note that "files" is always prepended while "systemd" is appended if nscd is enabled. This option only takes effect if nscd is enabled. ''; default = []; }; group = mkOption { type = types.listOf types.str; description = '' List of group entries to configure in /etc/nsswitch.conf. Note that "files" is always prepended while "systemd" is appended if nscd is enabled. This option only takes effect if nscd is enabled. ''; default = []; }; shadow = mkOption { type = types.listOf types.str; description = '' List of shadow entries to configure in /etc/nsswitch.conf. Note that "files" is always prepended. This option only takes effect if nscd is enabled. ''; default = []; }; hosts = mkOption { type = types.listOf types.str; description = '' List of hosts entries to configure in /etc/nsswitch.conf. Note that "files" is always prepended, and "dns" and "myhostname" are always appended. This option only takes effect if nscd is enabled. ''; default = []; }; services = mkOption { type = types.listOf types.str; description = '' List of services entries to configure in /etc/nsswitch.conf. Note that "files" is always prepended. This option only takes effect if nscd is enabled. ''; default = []; }; }; }; imports = [ (mkRenamedOptionModule [ "system" "nssHosts" ] [ "system" "nssDatabases" "hosts" ]) ]; 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. environment.etc."nsswitch.conf".text = '' passwd: ${concatStringsSep " " config.system.nssDatabases.passwd} group: ${concatStringsSep " " config.system.nssDatabases.group} shadow: ${concatStringsSep " " config.system.nssDatabases.shadow} hosts: ${concatStringsSep " " config.system.nssDatabases.hosts} networks: files ethers: files services: ${concatStringsSep " " config.system.nssDatabases.services} protocols: files rpc: files ''; system.nssDatabases = { passwd = passwdArray; group = passwdArray; shadow = shadowArray; hosts = hostArray; services = mkBefore [ "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 ]) ++ optional googleOsLogin pkgs.google-compute-engine-oslogin.out; }; }