systemd: use sd-switch by default

Also remove the legacy Ruby alternative.

Fixes #5452

docs/release-notes/rl-2505.md

@@ -7,7 +7,15 @@ section is therefore not final.
 
 This release has the following notable changes:
 
-- No changes.
+- The [](#opt-systemd.user.startServices) option now defaults to
+  `true`, meaning that services will automatically be restarted as
+  needed when activating a configuration.
+
+  Further, the `"legacy"` alternative has been removed and will now
+  result in an evaluation error if used.
+
+  The `"suggest"` alternative will remain for a while longer but may
+  also be deprecated for removal in the future.
 
 ## State Version Changes {#sec-release-25.05-state-version-changes}
 

modules/misc/news.nix

@@ -1919,6 +1919,22 @@ in {
           Cavalier is a GUI wrapper around the Cava audio visualizer.
         '';
       }
+
+      {
+        time = "2025-01-01T15:31:15+00:00";
+        condition = hostPlatform.isLinux;
+        message = ''
+          The 'systemd.user.startServices' option now defaults to 'true',
+          meaning that services will automatically be restarted as needed when
+          activating a configuration.
+
+          Further, the "legacy" alternative has been removed and will now result
+          in an evaluation error if used.
+
+          The "suggest" alternative will remain for a while longer but may also
+          be deprecated for removal in the future.
+        '';
+      }
     ];
   };
 }

modules/systemd-activate.rb

@@ -1,216 +0,0 @@
-require 'set'
-require 'open3'
-
-@dry_run = ENV['DRY_RUN']
-@verbose = ENV['VERBOSE']
-
-UnitsDir = 'home-files/.config/systemd/user'
-
-# 1. Stop all services from the old generation that are not present in the new generation.
-# 2. Ensure all services from the new generation that are wanted by active targets are running:
-#    - Start services that are not already running.
-#    - Restart services whose unit config files have changed between generations.
-# 3. If any services were (re)started, wait 'start_timeout_ms' and report services
-#    that failed to start. This helps debugging quickly failing services.
-#
-# Whenever service failures are detected, show the output of
-# 'systemd --user status' for the affected services.
-#
-def setup_services(old_gen_path, new_gen_path, start_timeout_ms_string)
-  start_timeout_ms = start_timeout_ms_string.to_i
-
-  old_units_path = File.join(old_gen_path, UnitsDir) unless old_gen_path.empty?
-  new_units_path = File.join(new_gen_path, UnitsDir)
-
-  old_services = get_services(old_units_path)
-  new_services = get_services(new_units_path)
-
-  exit if old_services.empty? && new_services.empty?
-
-  all_services = get_active_targets_units(new_units_path)
-  maybe_changed = all_services & old_services
-  changed_services = get_changed_services(old_units_path, new_units_path, maybe_changed)
-  unchanged_oneshots = get_oneshot_services(maybe_changed - changed_services)
-
-  # These services should be running when this script is finished
-  services_to_run = all_services - unchanged_oneshots
-
-  # Only stop active services, otherwise we might get a 'service not loaded' error
-  # for inactive services that were removed in the current generation.
-  to_stop = get_active_units(old_services - new_services)
-  to_restart = changed_services
-  to_start = get_inactive_units(services_to_run - to_restart)
-
-  raise "daemon-reload failed" unless run_cmd('systemctl', '--user', 'daemon-reload')
-
-  # Exclude units that shouldn't be (re)started or stopped
-  no_manual_start, no_manual_stop, no_restart = get_restricted_units(to_stop + to_restart + to_start)
-  notify_skipped_units(to_restart & no_restart)
-  to_stop -= no_manual_stop
-  to_restart -= no_manual_stop + no_manual_start + no_restart
-  to_start -= no_manual_start
-
-  if to_stop.empty? && to_start.empty? && to_restart.empty?
-    print_service_msg("All services are already running", services_to_run)
-  else
-    puts "Setting up services" if @verbose
-    systemctl_action('stop', to_stop)
-    systemctl_action('start', to_start)
-    systemctl_action('restart', to_restart)
-    started_services = to_start + to_restart
-    if start_timeout_ms > 0 && !started_services.empty? && !@dry_run
-      failed = wait_and_get_failed_services(started_services, start_timeout_ms)
-      if failed.empty?
-        print_service_msg("All services are running", services_to_run)
-      else
-        puts
-        puts "Error. These services failed to start:", failed
-        show_failed_services_status(failed)
-        exit 1
-      end
-    end
-  end
-end
-
-def get_services(dir)
-  services = get_service_files(dir) if dir && Dir.exists?(dir)
-  Set.new(services)
-end
-
-def get_service_files(dir)
-  Dir.chdir(dir) { Dir['*[^@].{service,socket,timer}'] }
-end
-
-def get_changed_services(dir_a, dir_b, services)
-  services.select do |service|
-    a = File.join(dir_a, service)
-    b = File.join(dir_b, service)
-    (File.size(a) != File.size(b)) || (File.read(a) != File.read(b))
-  end
-end
-
-TargetDirRegexp = /^(.*\.target)\.wants$/
-
-# @return all units wanted by active targets
-def get_active_targets_units(units_dir)
-  return Set.new unless Dir.exists?(units_dir)
-  targets = Dir.entries(units_dir).map { |entry| entry[TargetDirRegexp, 1] }.compact
-  active_targets = get_active_units(targets)
-  active_units = active_targets.map do |target|
-    get_service_files(File.join(units_dir, "#{target}.wants"))
-  end.flatten
-  Set.new(active_units)
-end
-
-# @return true on success
-def run_cmd(*cmd)
-  print_cmd cmd
-  @dry_run || system(*cmd)
-end
-
-def systemctl_action(cmd, services)
-  return if services.empty?
-
-  verb = (cmd == 'stop') ? 'Stopping' : "#{cmd.capitalize}ing"
-  puts "#{verb}: #{services.join(' ')}"
-
-  cmd = ['systemctl', '--user', cmd, *services]
-  if @dry_run
-    puts cmd.join(' ')
-    return
-  end
-
-  output, status = Open3.capture2e(*cmd)
-  print output
-  # Show status for failed services
-  unless status.success?
-    # Due to a bug in systemd, the '--user' argument is not always provided
-    output.scan(/systemctl (?:--user )?(status .*?)['"]/).flatten.each do |status_cmd|
-      puts
-      run_cmd("systemctl --user #{status_cmd}")
-    end
-    exit 1
-  end
-end
-
-def systemctl(*cmd)
-  output, _ = Open3.capture2('systemctl', '--user', *cmd)
-  output
-end
-
-def print_cmd(cmd)
-  puts [*cmd].join(' ') if @verbose || @dry_run
-end
-
-def get_active_units(units)
-  filter_units(units) { |state| state == 'active' }
-end
-
-def get_inactive_units(units)
-  filter_units(units) { |state| state != 'active' }
-end
-
-def get_failed_units(units)
-  filter_units(units) { |state| state == 'failed' }
-end
-
-def filter_units(units)
-  return [] if units.empty?
-  states = systemctl('is-active', *units).split
-  units.select.with_index { |_, i| yield states[i] }
-end
-
-def get_oneshot_services(units)
-  return [] if units.empty?
-  types = systemctl('show', '-p', 'Type', *units).split
-  units.select.with_index do |_, i|
-    types[i] == 'Type=oneshot'
-  end
-end
-
-def get_restricted_units(units)
-  infos = systemctl('show', '-p', 'RefuseManualStart', '-p', 'RefuseManualStop', *units)
-          .split("\n\n")
-  no_manual_start = []
-  no_manual_stop = []
-  infos.zip(units).each do |info, unit|
-    no_start, no_stop = info.split("\n")
-    no_manual_start << unit if no_start.end_with?('yes')
-    no_manual_stop << unit if no_stop.end_with?('yes')
-  end
-  # Get units that should not be restarted even if a change has been detected.
-  no_restart_regexp = /^\s*X-RestartIfChanged\s*=\s*false\b/
-  no_restart = units.select { |unit| systemctl('cat', unit) =~ no_restart_regexp }
-  [no_manual_start, no_manual_stop, no_restart]
-end
-
-def wait_and_get_failed_services(services, start_timeout_ms)
-  puts "Waiting #{start_timeout_ms} ms for services to fail"
-  # Force the previous message to always be visible before sleeping
-  STDOUT.flush
-  sleep(start_timeout_ms / 1000.0)
-  get_failed_units(services)
-end
-
-def show_failed_services_status(services)
-  puts
-  services.each do |service|
-    run_cmd('systemctl', '--user', 'status', service)
-    puts
-  end
-end
-
-def print_service_msg(msg, services)
-  return if services.empty?
-  if @verbose
-    puts "#{msg}:", services.to_a
-  else
-    puts msg
-  end
-end
-
-def notify_skipped_units(no_restart)
-  puts "Not restarting: #{no_restart.join(' ')}" unless no_restart.empty?
-end
-
-setup_services(*ARGV)

modules/systemd.nix

@@ -180,10 +180,9 @@ in {
       };
 
       startServices = mkOption {
-        default = "suggest";
+        type = with types; either bool (enum [ "suggest" "sd-switch" ]);
-        type = with types;
+        apply = p: if isBool p then p else p == "sd-switch";
-          either bool (enum [ "suggest" "legacy" "sd-switch" ]);
+        default = true;
-        apply = p: if isBool p then if p then "sd-switch" else "suggest" else p;
         description = ''
           Whether new or changed services that are wanted by active targets
           should be started. Additionally, stop obsolete services from the
@@ -196,12 +195,6 @@ in {
             {command}`systemctl` commands to run. You will have to
             manually run those commands after the switch.
 
-          `legacy`
-          : Use a Ruby script to, in a more robust fashion, determine the
-            necessary changes and automatically run the
-            {command}`systemctl` commands. Note, this alternative will soon
-            be removed.
-
           `sd-switch` (or `true`)
           : Use sd-switch, a tool that determines the necessary changes and
             automatically apply them.
@@ -297,12 +290,6 @@ in {
       message = "This module is only available on Linux.";
     }];
 
-    warnings = lib.optional (cfg.startServices == "legacy") ''
-      Having 'systemd.user.startServices = "legacy"' is deprecated and will soon be removed.
-
-      Please change to 'systemd.user.startServices = true' to use the new systemd unit switcher (sd-switch).
-    '';
-
     xdg.configFile = mkMerge [
       (lib.listToAttrs ((buildServices "service" cfg.services)
         ++ (buildServices "slice" cfg.slices)
@@ -323,26 +310,23 @@ in {
     # set and systemd commands will fail. We'll therefore have to
     # set it ourselves in that case.
     home.activation.reloadSystemd = hm.dag.entryAfter [ "linkGeneration" ] (let
-      cmd = {
+      suggestCmd = ''
-        suggest = ''
+        bash ${./systemd-activate.sh} "''${oldGenPath=}" "$newGenPath"
-          bash ${./systemd-activate.sh} "''${oldGenPath=}" "$newGenPath"
+      '';
-        '';
+
-        legacy = ''
+      sdSwitchCmd = let
-          ${pkgs.ruby}/bin/ruby ${./systemd-activate.rb} \
+        timeoutArg = if cfg.servicesStartTimeoutMs != 0 then
-            "''${oldGenPath=}" "$newGenPath" "${servicesStartTimeoutMs}"
+          "--timeout " + servicesStartTimeoutMs
-        '';
+        else
-        sd-switch = let
+          "";
-          timeoutArg = if cfg.servicesStartTimeoutMs != 0 then
+      in ''
-            "--timeout " + servicesStartTimeoutMs
+        ${lib.getExe pkgs.sd-switch} \
-          else
+          ''${DRY_RUN:+--dry-run} $VERBOSE_ARG ${timeoutArg} \
-            "";
+          ''${oldUnitsDir:+--old-units $oldUnitsDir} \
-        in ''
+          --new-units "$newUnitsDir"
-          ${lib.getExe pkgs.sd-switch} \
+      '';
-            ''${DRY_RUN:+--dry-run} $VERBOSE_ARG ${timeoutArg} \
+
-            ''${oldUnitsDir:+--old-units $oldUnitsDir} \
+      systemdCmd = if cfg.startServices then sdSwitchCmd else suggestCmd;
-            --new-units "$newUnitsDir"
-        '';
-      };
 
       # Make sure that we have an environment where we are likely to
       # successfully talk with systemd.
@@ -374,7 +358,7 @@ in {
           newUnitsDir=${pkgs.emptyDirectory}
         fi
 
-        ${ensureSystemd} ${getAttr cfg.startServices cmd}
+        ${ensureSystemd} ${systemdCmd}
 
         unset newUnitsDir oldUnitsDir
       else

tests/integration/nixos/basics.nix

@@ -21,9 +21,6 @@
       home.file.test.text = "testfile";
       # Enable a light-weight systemd service.
       services.pueue.enable = true;
-      # We focus on sd-switch since that hopefully will become the default in
-      # the future.
-      systemd.user.startServices = "sd-switch";
     };
   };
 

tests/integration/standalone/alice-home-next.nix

@@ -12,8 +12,4 @@
 
   # Enable a light-weight systemd service.
   services.pueue.enable = true;
-
-  # We focus on sd-switch since that hopefully will become the default in the
-  # future.
-  systemd.user.startServices = "sd-switch";
 }