nixos/switch-to-configuration: reload user units

When rebuilding you have to manually run `systemctl --user
daemon-reload`. It gathers all authenticated users using
`loginctl list-user` and runs `daemon-reload` for each of them.

This is a first step towards a `nixos-rebuild` which is able to reload
user units from systemd. The entire task is fairly hard, however I
consider this patch usable as it allows to restart units without running
`daemon-reload` for each authenticated user.

1 files changed, 12 insertions, 0 deletions

diff --git a/nixos/modules/system/activation/switch-to-configuration.pl b/nixos/modules/system/activation/switch-to-configuration.pl
index ecd35767e01d..b3fe6caf62dc 100644
--- a/nixos/modules/system/activation/switch-to-configuration.pl
+++ b/nixos/modules/system/activation/switch-to-configuration.pl
@@ -412,6 +412,18 @@ system("@systemd@/bin/systemctl", "reset-failed");
 # Make systemd reload its units.
 system("@systemd@/bin/systemctl", "daemon-reload") == 0 or $res = 3;
 
+# Reload user units
+open my $listActiveUsers, '-|', '@systemd@/bin/loginctl', 'list-users', '--no-legend';
+while (my $f = <$listActiveUsers>) {
+    next unless $f =~ /^\s*(?<uid>\d+)\s+(?<user>\S+)/;
+    my ($uid, $name) = ($+{uid}, $+{user});
+    print STDERR "reloading user units for $name...\n";
+
+    system("su", "-l", $name, "-c", "XDG_RUNTIME_DIR=/run/user/$uid @systemd@/bin/systemctl --user daemon-reload");
+}
+
+close $listActiveUsers;
+
 # Set the new tmpfiles
 print STDERR "setting up tmpfiles\n";
 system("@systemd@/bin/systemd-tmpfiles", "--create", "--remove", "--exclude-prefix=/dev") == 0 or $res = 3;