Dbus breaks Xfce + VNC

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Dbus breaks Xfce + VNC

Postby goingarm » Sun Sep 04, 2016 7:37 pm

The latest dbus update, which somehow merged libdbus into dbus, breaks Xfce VNC sessions.
I would downgrade, but unlike on archlinux.org I don't find older packages here.
Can you tell me how to downgrade? I don't have an older dbus package in my cache, sadly.

Please forgive my poor formatting. I don't have access to my ARM computer because of this bug.
Problem is described in detail by another user here:
https://bbs.archlinux.org/viewtopic.php?id=216491
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Re: Dbus breaks Xfce + VNC

Postby modul » Sun Sep 04, 2016 9:27 pm

Someone provides a package archive:

http://tardis.tiny-vps.com/aarm/
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Re: Dbus breaks Xfce + VNC

Postby goingarm » Mon Sep 05, 2016 8:05 am

Is there any way one can be sure those packages are safe and haven't been tempered with?
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Re: Dbus breaks Xfce + VNC

Postby andreworg » Mon Sep 05, 2016 12:14 pm

Same thing here. I run two different sessions, as different users; strangely, one seems to be working, the other does not.

I have had success by running xfce4-session again manually, after running vncserver (the server itself does not crash).
Open a terminal session and run this as the user running vncserver:

Code: Select all
DISPLAY=:1 xfce4-session

of course DISPLAY=:n must match your vncserver session display number.

EDIT:
the session seems to crash as soon as I put the xfce4-session process to background.
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Re: Dbus breaks Xfce + VNC

Postby goingarm » Mon Sep 05, 2016 7:16 pm

I think that workaround only works for real X sessions (with keyboard and mouse), but not virtual ones? Maybe that's why only 1 of your VNC sessions work?
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Re: Dbus breaks Xfce + VNC

Postby andreworg » Wed Sep 07, 2016 1:45 am

Nope, it works in tigervnc. The workaround works for the session running as the user having the issue; the session opened as the other user does not have any issues and works perfectly as before. I still haven't understood what the root cause is. It is not the order in which I open the sessions - I tried swapping it and nothing changes. One strange thing that I noticed is that I am not able to background the xfce4-session process in any way; I get the original error as soon as I try. I had to resort to running the process in tmux.
EDITED TO ADD: also look at this: https://bbs.archlinux.org/viewtopic.php?id=216001
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Re: Dbus breaks Xfce + VNC

Postby goingarm » Fri Sep 09, 2016 4:43 pm

OK thanks andreworg, your DISPLAY workaround helps me access my machine again. For now it seems I can even put it in the background without crashing by adding a "&" to its command line.

But why is this necessary? The session somehow doesn't start on its own?
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Re: Dbus breaks Xfce + VNC

Postby andreworg » Fri Sep 09, 2016 7:08 pm

Glad to know my workaround helped you too.

Something wrong must be happening when xfce4-session is run by the VNC server's init process. As far as I can tell, it seems to have to do with the new version of dbus integrating libdbus. The mainline Arch forum thread I linked in my previous post shows several ideas and fixes, none of which worked in my case. It's also possible that there is something wrong related to permissions, at least on my system, since sessions started as one user come up just fine, when started as another user they invariantly crash.

EDITED TO ADD: this may explain the permission issue:

https://www.archlinux.org/news/d-bus-no ... ser-buses/
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Re: Dbus breaks Xfce + VNC

Postby goingarm » Sun Sep 11, 2016 8:09 pm

So it seems users since the new dbus update get a dbus address or somehow an initialization the moment they log on. When a user didn't log on before a VNC server is started, the user doesn't get a dbus address.
I start my VNC server via crontab - maybe that's why the user doesn't get "a dbus".
After manual log on via SSH I can start xcfe4-session and it then works. But starting it in the ~/.vnc/xstartup script won't work.

Is there any way to simulate a user log on? Maybe that would solve the problem. Ideally it could be put in a crontab or some other automated script.
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Re: Dbus breaks Xfce + VNC

Postby andreworg » Mon Sep 12, 2016 8:05 am

It must be something along the lines of what you said. My sessions fail when launched after switching (su) to a different user.
However, this does not explain why the session is working when I run it manually later. I am not doing anything different, actually using the very same terminal session as the one running tigervnc.
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