systemd: enable start services by default

This enables the use of sd-switch to reload, start, and stop services
as needed when switching configurations.

This also entirely removes the Ruby based service helper.

Fixes #5452

docs/release-notes/rl-2411.md

@@ -7,7 +7,19 @@ is therefore not final.
 
 This release has the following notable changes:
 
-- No changes.
+- The option
+  [systemd.user.startServices](#opt-systemd.user.startServices) now
+  defaults to `true`. This means that managed systemd services will be
+  automatically started and stopped as needed.
+
+  If you encounter errors please set the option to `false` in your
+  configuration:
+
+  ```nix
+  systemd.user.startServices = false
+  ```
+
+  Also, please report the error in the Home Manager issue tracker.
 
 ## State Version Changes {#sec-release-24.11-state-version-changes}
 

modules/misc/news.nix

@@ -1724,6 +1724,23 @@ in {
           editor).
         '';
       }
+
+      {
+        time = "2024-09-17T05:45:39+00:00";
+        condition = hostPlatform.isLinux;
+        message = ''
+          The option 'systemd.user.startServices' now defaults to 'true'. This
+          means that managed systemd services will be automatically started and
+          stopped as needed.
+
+          If you encounter errors please set the option to 'false' in your
+          configuration:
+
+             systemd.user.startServices = false
+
+          Also, please report the error in the Home Manager issue tracker.
+        '';
+      }
     ];
   };
 }

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";
+        default = true;
-        type = with types;
+        type = types.bool;
-          either bool (enum [ "suggest" "legacy" "sd-switch" ]);
+        apply = p: if p == "sd-switch" then true else p;
-        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
@@ -191,20 +190,14 @@ in {
 
           The alternatives are
 
-          `suggest` (or `false`)
+          `true` (the default)
+          : Use sd-switch, a tool that determines the necessary changes and
+            automatically apply them.
+
+          `false`
           : Use a very simple shell script to print suggested
             {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.
         '';
       };
 
@@ -327,10 +320,7 @@ in {
         suggest = ''
           bash ${./systemd-activate.sh} "''${oldGenPath=}" "$newGenPath"
         '';
-        legacy = ''
+
-          ${pkgs.ruby}/bin/ruby ${./systemd-activate.rb} \
-            "''${oldGenPath=}" "$newGenPath" "${servicesStartTimeoutMs}"
-        '';
         sd-switch = let
           timeoutArg = if cfg.servicesStartTimeoutMs != 0 then
             "--timeout " + servicesStartTimeoutMs