Allow upstream systemd units to be extended

If you define a unit, and either systemd or a package in
systemd.packages already provides that unit, then we now generate a
file /etc/systemd/system/<unit>.d/overrides.conf. This makes it
possible to use upstream units, while allowing them to be customised
from the NixOS configuration. For instance, the module nix-daemon.nix
now uses the units provided by the Nix package. And all unit
definitions that duplicated upstream systemd units are finally gone.

This makes the baseUnit option unnecessary, so I've removed it.

1 files changed, 4 insertions, 16 deletions

diff --git a/nixos/modules/services/misc/nix-daemon.nix b/nixos/modules/services/misc/nix-daemon.nix
index 1516736dc2e0..e6528777c325 100644
--- a/nixos/modules/services/misc/nix-daemon.nix
+++ b/nixos/modules/services/misc/nix-daemon.nix
@@ -275,28 +275,16 @@ in
           ) cfg.buildMachines;
       };
 
-    systemd.sockets."nix-daemon" =
-      { description = "Nix Daemon Socket";
-        wantedBy = [ "sockets.target" ];
-        before = [ "multi-user.target" ];
-        unitConfig.ConditionPathIsReadWrite = "/nix/var/nix/daemon-socket/";
-        socketConfig.ListenStream = "/nix/var/nix/daemon-socket/socket";
-      };
-
-    systemd.services."nix-daemon" =
-      { description = "Nix Daemon";
+    systemd.packages = [ nix ];
 
-        path = [ nix pkgs.openssl pkgs.utillinux pkgs.openssh ]
+    systemd.services.nix-daemon =
+      { path = [ nix pkgs.openssl pkgs.utillinux pkgs.openssh ]
           ++ optionals cfg.distributedBuilds [ pkgs.gzip ];
 
         environment = cfg.envVars // { CURL_CA_BUNDLE = "/etc/ssl/certs/ca-bundle.crt"; };
 
-        unitConfig.ConditionPathIsReadWrite = "/nix/var/nix/daemon-socket/";
-
         serviceConfig =
-          { ExecStart = "@${nix}/bin/nix-daemon nix-daemon --daemon";
-            KillMode = "process";
-            Nice = cfg.daemonNiceLevel;
+          { Nice = cfg.daemonNiceLevel;
             IOSchedulingPriority = cfg.daemonIONiceLevel;
             LimitNOFILE = 4096;
           };