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nixpkgs/nixos/modules/config/nsswitch.nix

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Nix

# Configuration for the Name Service Switch (/etc/nsswitch.conf).
{ config, lib, ... }:
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" ]
++ optional mymachines "mymachines"
++ optional nssmdns "mdns_minimal [NOTFOUND=return]"
++ optional nsswins "wins"
++ optional resolved "resolve [!UNAVAIL=return]"
++ [ "dns" ]
++ optional nssmdns "mdns"
++ optional myhostname "myhostname";
passwdArray = [ "files" ]
++ optional sssd "sss"
++ optional ldap "ldap"
++ optional mymachines "mymachines"
++ [ "systemd" ];
shadowArray = [ "files" ]
++ optional sssd "sss"
++ optional 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
<filename>/etc/nsswitch.conf</filename>.
'';
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 ];
};
}