Merge pull request #28206 from edef1c/net-dbus-list-units

switch-to-configuration: use Net::DBus to retrieve the list of units

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

@@ -4,6 +4,7 @@
 use warnings;
 use File::Basename;
 use File::Slurp;
+use Net::DBus;
 use Sys::Syslog qw(:standard :macros);
 use Cwd 'abs_path';
 
@@ -67,17 +68,15 @@
 $SIG{PIPE} = "IGNORE";
 
 sub getActiveUnits {
-    # FIXME: use D-Bus or whatever to query this, since parsing the
-    # output of list-units is likely to break.
-    # Use current version of systemctl binary before daemon is reexeced.
-    my $lines = `LANG= /run/current-system/sw/bin/systemctl list-units --full --no-legend`;
+    my $mgr = Net::DBus->system->get_service("org.freedesktop.systemd1")->get_object("/org/freedesktop/systemd1");
+    my $units = $mgr->ListUnitsByPatterns([], []);
     my $res = {};
-    foreach my $line (split '\n', $lines) {
-        chomp $line;
-        last if $line eq "";
-        $line =~ /^(\S+)\s+(\S+)\s+(\S+)\s+(\S+)\s/ or next;
-        next if $1 eq "UNIT";
-        $res->{$1} = { load => $2, state => $3, substate => $4 };
+    for my $item (@$units) {
+        my ($id, $description, $load_state, $active_state, $sub_state,
+            $following, $unit_path, $job_id, $job_type, $job_path) = @$item;
+        next unless $following eq '';
+        next if $job_id == 0 and $active_state eq 'inactive';
+        $res->{$id} = { load => $load_state, state => $active_state, substate => $sub_state };
     }
     return $res;
 }

nixos/modules/system/activation/top-level.nix

@@ -127,7 +127,8 @@ let
       configurationName = config.boot.loader.grub.configurationName;
 
       # Needed by switch-to-configuration.
-      perl = "${pkgs.perl}/bin/perl -I${pkgs.perlPackages.FileSlurp}/lib/perl5/site_perl";
+
+      perl = "${pkgs.perl}/bin/perl " + (concatMapStringsSep " " (lib: "-I${lib}/${pkgs.perl.libPrefix}") (with perlPackages; [ FileSlurp NetDBus XMLParser XMLTwig ]));
   } else throw "\nFailed assertions:\n${concatStringsSep "\n" (map (x: "- ${x}") failed)}");
 
   # Replace runtime dependencies