start window manager with "dbus-launch"?

djqwzlcsz · n00b Joined: 19 Dec 2020 Posts: 16

Hello,

on Debian I always had "exec bspwm" in my .xinitrc file to start my window manager with startx.
Since elogind was required to emerge x11-base/xorg-server I've read the Wiki page about elogind.
It says I should put "exec dbus-launch --exit-with-session <WINDOW_MANAGER>" in my .xinitrc.

How is the above different to just running "exec bspwm"? Which one is "better"? What will I gain?

eccerr0r · Posted: Sun Dec 20, 2020 12:00 am Post subject:

You should have been able to disable elogind support if you don't want it, though I'm not sure about the consequences of doing such from your setup.

With the legacy windowmanagers out there which do not provide services to simplify access to console attached devices, there probably is no need for elogind/systemd support anyway, unless you run something that uses the support beyond the windowmanager, perhaps like one of the file managers from a full desktop environment.

Since it seems that you were "forced" to use elogind, then I'd say you should rebuild everything with USE=-elogind to revert to previous behavior and all is better - no need to set up a session through dbus.
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Hu · Administrator Joined: 06 Mar 2007 Posts: 23663

The requested change runs a DBUS session, with your window manager and all the children thereof under it. This will give those processes access to a common DBUS session. Per eccerr0r's post, this may not actually gain you anything that you care about.

figueroa · Posted: Sun Dec 20, 2020 3:37 am Post subject:

My .xintrc which I recommend. Substitute your own WM if you are not using openbox:

djqwzlcsz · n00b Joined: 19 Dec 2020 Posts: 16

I've read the dbus-launch man page and honestly I didn't learn anything useful...
Yes it is a "a wrapper around the main X client" and it will "start a session bus instance of dbus-daemon".
But I can't imagine what that actually means...

The dbus-daemon man page was a little bit more informing.
So now I know dbus is something that makes various applications able to communicate with each other.

That't the theory. But I still don't know if I need that or not. What will I gain or loose?
Puhh...

Currently I'm running Gentoo in a VM anyway... guess I'll just go back some snapshots and try it with USE -elogind.
Guess I'll see if I miss anything or not.

btw. Yes I am using "one of the file managers from a full desktop environment". PCManFM... if that counts

Naib · Posted: Sun Dec 20, 2020 10:33 am Post subject:

You might not need it. You might not be running applications that need a user IPC (assuming it cannot use the system wide instance)

I have only ever used: windowmaker,openbox,awesomewm and then just launch the apps I want and thus without a classic DM that might require an IPC, I never did.
I recently switched to pipewire and it does need it so finally I have a need to launch a user dbus session.

So... You can either launch one as a just in case or wait until some application requires it to communicate with other applications
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GDH-gentoo · Posted: Sun Dec 20, 2020 2:32 pm Post subject:

Exactly. Using dbus-launch to start the window manager also launches a per-login session message bus. It doesn't matter whether you are using elogind (which connects the system-wide message bus, a different bus instance launched by the init system) or if Xorg is running as root. What matters is whether you are using applications that want to connect to the session bus. If you are using elogind, you can use busctl to find out:

figueroa · Posted: Sun Dec 20, 2020 2:46 pm Post subject:

eccerr0r · Posted: Sun Dec 20, 2020 4:41 pm Post subject:

I know there are die hard classic UN*X environment fans out there that believe console should be just another unprivileged dumb terminal, and sometimes it's hard to keep them satisfied too. While software technology goes on, just keeping the "session/seat" deal going generally lets less problems show up ("go with the flow"), there indeed are situations that you simply don't need elogind/systemd services...

I'd view it more of not "wards off problems" but "provides a way to remove seams" but if the software you're using doesn't take advantage of the seam removal, then these services are just adding more bloat. Generally I also view the console/session/seat paradigm a "good thing" and "useful" as well, but sometimes it's simply not necessary. It's up to the person setting up the machine to decide.

Question still remains - what downstream software is being used that could possibly take advantage of the console. If the person just wants to treat the console as a dumb video terminal and nothing else (no disk drives, no USB ports, no sound, etc.) and the software has its own way to communicate among its pieces (own shared memory mechanisms) then these are not necessary.

(One example that I find that's a wonderful use of dbus that's not strictly console related is the screen saver. Using the dbus api, a movie player application can trigger the screensaver to not kick in, but once the movie player exits, it will no longer trigger the screensaver and the screensaver can then turn off the display. Nothing is more annoying than watching a movie and the screensaver kicks in, but you wouldn't (always) want something like gkrellm to keep the screen from blanking/shutting down when you're not there.)
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figueroa · Posted: Mon Dec 21, 2020 3:36 am Post subject:

I've got 8 threads in 4 cores + 16 GB RAM. Why would I care about a few bytes of memory and a bogomip here or there. The default recommended configuration works well for me and will probably be best for most user. I don't think it's a good use of my time avoid elogind and dbus. I accept their benefits and I'm happy about it. On most days, I consider it a miracle when the GUI shows up after I log back in.
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djqwzlcsz · n00b Joined: 19 Dec 2020 Posts: 16

figueroa · Posted: Mon Dec 21, 2020 4:23 pm Post subject:

If you read your unread news you'll find the answers.

djqwzlcsz · n00b Joined: 19 Dec 2020 Posts: 16

Yes I've already read that.
It says I should just enable elogind or suid.
But it doesn't work.

EDIT:
hmm... if I run "startx -- vt1" instead of "startx" this works fine and my X starts...
Is it required to do this on Gentoo or do I have any problem in my configs?

Hu · Administrator Joined: 06 Mar 2007 Posts: 23663

How did you enable elogind? Does the command mentioned in the news indicate that you have a session open?

djqwzlcsz · n00b Joined: 19 Dec 2020 Posts: 16

I added USE="elogind" to "/etc/portage/make.conf" and then did a "emerge --ask --changed-use --deep @world".

No it didn't say I have a session open.
This should say I have a session open after I login via tty? Or only after starting X?

btw. the command "startx -- vt1" also works when I emerged xorg-server without elogind, systemd or suid.
(-elogind -systemd in make.conf and xserver-xorg -suid in package.use)

well now I'm completely 100% confused.

Hu · Administrator Joined: 06 Mar 2007 Posts: 23663

You need a session to be able to start X without special arguments. From your lack of mention, I think you neither set elogind to start on boot, nor started it manually. Please run rc-update add elogind default ; /etc/init.d/elogind start as root, then log in as your regular user at a text console and try again.

GDH-gentoo · Posted: Mon Dec 21, 2020 10:44 pm Post subject:

djqwzlcsz · n00b Joined: 19 Dec 2020 Posts: 16

Thank you all for taking the time to help me with this issue.

I'm not using a desktop profile but the hardened profile instead.
So I've to set the flags manually.

I've done the following now:
Add elogind use flag to make.conf
Add -suid for x11-base/xorg-server in package.use
emerge --ask --verbose --update --deep --newuse --quiet @world
rc-update add elogind boot

After a reboot loginctl shows that I have a session.
"startx" worked without any special arguments.

However XDG_VTNR is not set.

GDH-gentoo · Posted: Tue Dec 22, 2020 10:50 pm Post subject:

figueroa · Posted: Wed Dec 23, 2020 2:27 am Post subject:

For what it's worth, under lightdm:

djqwzlcsz · n00b Joined: 19 Dec 2020 Posts: 16

Oh I know what it was.

via SSH:

eccerr0r · Posted: Wed Dec 23, 2020 4:51 pm Post subject:

Yeah, one thing about the logind seats is that it makes sessions real clear that it's a child of remote access or from a terminal emulator on console in X.

Both are assigned a pseudo teletype (pty) but only one of these gets console access through polkit.
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