Merge branch 'containers'

Fixes #2105.

nixos/modules/system/activation/switch-to-configuration.pl

@@ -26,7 +26,10 @@ EOF
     exit 1;
 }
 
-die "This is not a NixOS installation (/etc/NIXOS is missing)!\n" unless -f "/etc/NIXOS";
+# This is a NixOS installation if it has /etc/NIXOS or a proper
+# /etc/os-release.
+die "This is not a NixOS installation!\n" unless
+    -f "/etc/NIXOS" || (read_file("/etc/os-release", err_mode => 'quiet') // "") =~ /ID=nixos/s;
 
 openlog("nixos", "", LOG_USER);
 
@@ -173,7 +176,10 @@ while (my ($unit, $state) = each %{$activePrev}) {
                 # FIXME: do something?
             } else {
                 my $unitInfo = parseUnit($newUnitFile);
-                if (!boolIsTrue($unitInfo->{'X-RestartIfChanged'} // "yes")) {
+                if (boolIsTrue($unitInfo->{'X-ReloadIfChanged'} // "no")) {
+                    write_file($reloadListFile, { append => 1 }, "$unit\n");
+                }
+                elsif (!boolIsTrue($unitInfo->{'X-RestartIfChanged'} // "yes")) {
                     push @unitsToSkip, $unit;
                 } else {
                     # If this unit is socket-activated, then stop the
@@ -321,7 +327,7 @@ if (scalar @restart > 0) {
 # that are symlinks to other units.  We shouldn't start both at the
 # same time because we'll get a "Failed to add path to set" error from
 # systemd.
-my @start = unique("default.target", "timers.target", split('\n', read_file($startListFile, err_mode => 'quiet') // ""));
+my @start = unique("default.target", "timers.target", "sockets.target", split('\n', read_file($startListFile, err_mode => 'quiet') // ""));
 print STDERR "starting the following units: ", join(", ", sort(@start)), "\n";
 system("@systemd@/bin/systemctl", "start", "--", @start) == 0 or $res = 4;
 unlink($startListFile);

nixos/modules/system/boot/systemd-unit-options.nix

@@ -243,6 +243,17 @@ in rec {
       '';
     };
 
+    reloadIfChanged = mkOption {
+      type = types.bool;
+      default = false;
+      description = ''
+        Whether the service should be reloaded during a NixOS
+        configuration switch if its definition has changed.  If
+        enabled, the value of <option>restartIfChanged</option> is
+        ignored.
+      '';
+    };
+
     stopIfChanged = mkOption {
       type = types.bool;
       default = true;

nixos/modules/system/boot/systemd.nix

@@ -279,7 +279,11 @@ let
           [Service]
           ${let env = cfg.globalEnvironment // def.environment;
             in concatMapStrings (n: "Environment=\"${n}=${getAttr n env}\"\n") (attrNames env)}
-          ${optionalString (!def.restartIfChanged) "X-RestartIfChanged=false"}
+          ${if def.reloadIfChanged then ''
+            X-ReloadIfChanged=true
+          '' else if !def.restartIfChanged then ''
+            X-RestartIfChanged=false
+          '' else ""}
           ${optionalString (!def.stopIfChanged) "X-StopIfChanged=false"}
           ${attrsToSection def.serviceConfig}
         '';