port service manager to s6

still a lot of cleanup to do (e.g. support dbus service types), but it boots to a usable desktop

hosts/common/programs/assorted.nix

@@ -79,6 +79,8 @@ in
       "powertop"
       "pstree"
       "ripgrep"
+      "s6"
+      "s6-rc"  # service manager
       "screen"
       "smartmontools"  # smartctl
       # "socat"
@@ -763,6 +765,9 @@ in
 
     rustc = {};
 
+    s6 = {};
+    s6-rc = {};
+
     sane-open-desktop.sandbox.enable = false;  #< trivial script, and all our deps are sandboxed
     sane-open-desktop.suggestedPrograms = [
       "gdbus"

hosts/common/programs/sway/default.nix

@@ -16,7 +16,10 @@ let
       export XDG_CURRENT_DESKTOP=sway
 
       echo "launching sway (sway.desktop)..." | ${systemd-cat} --identifier=sway
-      exec ${configuredSway}/bin/sway 2>&1 | ${systemd-cat} --identifier=sway
+      # delete DISPLAY-related vars from env before launch, else sway will try to connect to a remote display.
+      # (consider: nested sway sessions, where sway actually has a reason to read these)
+      exec env -u DISPLAY -u WAYLAND_DISPLAY \
+        ${configuredSway}/bin/sway 2>&1 | ${systemd-cat} --identifier=sway
     '';
   in
     pkgs.symlinkJoin {
@@ -194,6 +197,7 @@ in
       # bind ALL of ~/.config/sway into the sandbox instead of just the individual configs.
       # this way `swaymsg -- reload` can work even if the fd for ~/.config/sway/config changes.
       ".config/sway"
+      ".config/s6"
     ];
     sandbox.extraConfig = [
       "--sane-sandbox-keep-namespace" "pid"
@@ -218,26 +222,50 @@ in
       xwayland = if config.sane.programs.xwayland.enabled then "enable" else "disable";
     };
 
-    services.sway-session = {
+    env.XDG_CURRENT_DESKTOP = "sway";
-      description = "sway-session: active iff sway desktop environment is baseline operational";
+    # TODO: don't hardcode user id!
-      documentation = [
+    env.SWAYSOCK = "/run/user/1000/sway-ipc.sock";
-        "https://github.com/swaywm/sway/issues/7862"
+    # TODO: ensure this is reliable? might not work across sway restarts, etc.
-        "https://github.com/alebastr/sway-systemd"
+    env.DISPLAY = ":0";
-      ];
+    env.WAYLAND_DISPLAY = "wayland-1";
 
-      # we'd like to start graphical-session after sway is ready, but it's marked `RefuseManualStart` because Lennart.
+    # services.sway-session = {
-      # instead, create `sway-session.service` which `bindsTo` `graphical-session.target`.
+    #   description = "sway-session: active iff sway desktop environment is baseline operational";
-      # we can manually start `sway-session`, and the `bindsTo` means that it will start `graphical-session`,
+    #   documentation = [
-      # and then track `graphical-session`s state (that is: it'll stop when graphical-session stops).
+    #     "https://github.com/swaywm/sway/issues/7862"
-      #
+    #     "https://github.com/alebastr/sway-systemd"
-      # additionally, set `ConditionEnvironment` to guard that the sway environment variables *really have* been imported into systemd.
+    #   ];
-      unitConfig.ConditionEnvironment = "SWAYSOCK";
-      # requiredBy = [ "graphical-session.target" ];
-      before = [ "graphical-session.target" ];
-      bindsTo = [ "graphical-session.target" ];
 
+    #   # we'd like to start graphical-session after sway is ready, but it's marked `RefuseManualStart` because Lennart.
+    #   # instead, create `sway-session.service` which `bindsTo` `graphical-session.target`.
+    #   # we can manually start `sway-session`, and the `bindsTo` means that it will start `graphical-session`,
+    #   # and then track `graphical-session`s state (that is: it'll stop when graphical-session stops).
+    #   #
+    #   # additionally, set `ConditionEnvironment` to guard that the sway environment variables *really have* been imported into systemd.
+    #   unitConfig.ConditionEnvironment = "SWAYSOCK";
+    #   # requiredBy = [ "graphical-session.target" ];
+    #   before = [ "graphical-session.target" ];
+    #   bindsTo = [ "graphical-session.target" ];
+
+    #   serviceConfig = {
+    #     ExecStart = "${pkgs.coreutils}/bin/true";
+    #     Type = "oneshot";
+    #     RemainAfterExit = true;
+    #   };
+    # };
+
+    # services.sway-session = {
+    #   description = "sway-session: meta-service for everything wanted by sway (after launch)";
+    #   wants = [ "graphical-session.target" ];
+    # };
+
+    services.sway = {
+      description = "sway: launch it";
+      wantedBy = [ "default.target" ];
       serviceConfig = {
-        ExecStart = "${pkgs.coreutils}/bin/true";
+        ExecStart = "${cfg.package}/bin/sway";
+        # ExecStart = "${lib.getBin pkgs.glib}/bin/gio launch sway.desktop";
+        # ExecStart = "${pkgs.sane-open-desktop}/bin/sane-open-desktop sway.desktop";
         Type = "oneshot";
         RemainAfterExit = true;
       };

hosts/common/programs/sway/sway-config

@@ -258,6 +258,10 @@ exec --no-startup-id dbus-update-activation-environment --systemd PATH XDG_DATA_
 # signal to systemd that sway is active,
 # and therefore let it start any downstream services (e.g. apps that would like to auto-start)
 # see `systemctl --user cat sway-session` for links to docs
-exec --no-startup-id systemctl start --user sway-session.service
+# exec --no-startup-id systemctl start --user sway-session.service
+
+# TODO: remove this. likely, the variables above can/should be set *before* launching the service manager at all.
+#       and if need be we can replace this line with a "notify ready" signal to the service manager instead.
+exec --no-startup-id s6-rc -l $HOME/.config/s6/live start graphical-session
 
 @extra_lines@

hosts/common/programs/unl0kr/default.nix

@@ -119,15 +119,28 @@ in
       };
     };
 
-    # lib.mkAfter so that launching the DE happens *after* any other .profile setup.
+    fs.".profile".symlink.text = lib.mkMerge [
-    # alternatively, we could recurse: exec a new login shell with some env-var signalling to not launch the DE,
+      (lib.mkBefore ''
-    #   run with `-c "{cfg.afterLogin}"`
+        primarySessionCommands=()
-    fs.".profile".symlink.text = lib.mkAfter ''
+        initPrimarySession() {
-      # if already running a desktop environment, or if running from ssh, then `tty` will show /dev/pts/NN.
+          for c in "''${primarySessionCommands[@]}"; do
-      if [ "$(tty)" = "/dev/${tty}" ]; then
+            eval "$c"
-        ${tryLaunchDefaultDesktop}/bin/tryLaunchDefaultDesktop
+          done
-      fi
+        }
-    '';
+      '')
+      # lib.mkAfter so that launching the DE happens *after* any other .profile setup.
+      (lib.mkAfter ''
+        # if already running a desktop environment, or if running from ssh, then `tty` will show /dev/pts/NN.
+        if [ "$(tty)" = "/dev/${tty}" ]; then
+          if (( ''${#primarySessionCommands[@]} )); then
+            echo "launching primary session commands in ${builtins.toString cfg.config.delay}s: ''${primarySessionCommands[*]}"
+            # if the `sleep` call here is `Ctrl+C'd`, then it'll exit false and the desktop isn't launched.
+            sleep ${builtins.toString cfg.config.delay} && \
+              initPrimarySession
+          fi
+        fi
+      '')
+    ];
 
     # N.B.: this sandboxing applies to `unl0kr` itself -- the on-screen-keyboard;
     #       NOT to the wrapper which invokes `login`.

hosts/common/programs/xdg-desktop-portal.nix

@@ -59,19 +59,19 @@ in
       wantedBy = [ "graphical-session.target" ];
 
       serviceConfig = {
-        ExecStart="${cfg.package}/libexec/xdg-desktop-portal";
+        # tracking issue for having xdg-desktop-portal locate portals via more standard directories, obviating this var:
+        # - <https://github.com/flatpak/xdg-desktop-portal/issues/603>
+        # i can actually almost omit it today; problem is that if you don't set it it'll look for `sway-portals.conf` in ~/.config/xdg-desktop-portal
+        # but then will check its *own* output dir for {gtk,wlr}.portal.
+        # arguable if that's a packaging bug, or limitation...
+        ExecStart=''env XDG_DESKTOP_PORTAL_DIR="$HOME/.config/xdg-desktop-portal" ${cfg.package}/libexec/xdg-desktop-portal'';
         Type = "dbus";
         BusName = "org.freedesktop.portal.Desktop";
         Restart = "always";
         RestartSec = "10s";
       };
 
-      # tracking issue for having xdg-desktop-portal locate portals via more standard directories, obviating this var:
+      # environment.XDG_DESKTOP_PORTAL_DIR = "%E/xdg-desktop-portal";
-      # - <https://github.com/flatpak/xdg-desktop-portal/issues/603>
-      # i can actually almost omit it today; problem is that if you don't set it it'll look for `sway-portals.conf` in ~/.config/xdg-desktop-portal
-      # but then will check its *own* output dir for {gtk,wlr}.portal.
-      # arguable if that's a packaging bug, or limitation...
-      environment.XDG_DESKTOP_PORTAL_DIR = "%E/xdg-desktop-portal";
 
       # environment.G_MESSAGES_DEBUG = "all";  #< also applies to all apps launched by the portal
     };

modules/users/s6-rc.nix

@@ -103,7 +103,7 @@ let
       inherit name;
       run = service.serviceConfig.ExecStart;
       depends = service.wants ++ builtins.attrNames (
-        lib.filterAttrs (_: cfg: lib.elem name cfg.wantedBy) services
+        lib.filterAttrs (_: cfg: lib.elem name cfg.wantedBy || lib.elem "${name}.service" cfg.wantedBy) services
       );
     })
     services
@@ -131,7 +131,46 @@ in
       sources = genServices (s6SvcsFromConfigServices (implicitServices // config.services));
     in {
       fs.".config/s6/sources".symlink.target = sources;
-      fs.".config/s6/compiled".symlink.target = compileServices sources;
+      # N.B.: `compiled` needs to be writable (for locks -- maybe i can use symlinks to dodge this someday),
+      # so write this nearby and copy it over to `compiled` later
+      fs.".config/s6/compiled-static".symlink.target = compileServices sources;
+
+      fs.".profile".symlink.text = ''
+        function startS6() {
+          local S6_TARGET="''${1:-default}"
+
+          local COMPILED=$HOME/.config/s6/compiled
+          local LIVE=$HOME/.config/s6/live
+          local SCANDIR=$HOME/.config/s6/scandir
+
+          rm -rf $SCANDIR
+          mkdir $SCANDIR
+          s6-svscan $SCANDIR &
+          local SVSCAN=$!
+
+          # the scandir is just links back into the compiled dir,
+          # so the compiled dir therefore needs to be writable:
+          rm -rf $COMPILED
+          cp --dereference -R $COMPILED-static $COMPILED
+          chmod -R 0700 $COMPILED
+
+          s6-rc-init -c $COMPILED -l $LIVE -d $SCANDIR
+
+          # echo default: deps
+          # s6-rc-db -c $COMPILED contents default
+          # echo graphical-session: deps
+          # s6-rc-db -c $COMPILED contents graphical-session
+
+          if [ -n "$S6_TARGET" ]; then
+            s6-rc -l $LIVE start "$S6_TARGET"
+          fi
+
+          echo "s6 initialized: Ctrl+C to stop"
+          wait $SVSCAN
+        }
+
+        primarySessionCommands+=('startS6 &')
+      '';
     }));
   };
 }