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I'm running Lubuntu 14.10. It seems that LighDM invokes /etc/X11/Xsession only if directed to so by the user. In fact there is no shadow of it in lightdm-session wrapper.

  • startx command line (wrapper around xinit for reasonable defaults) uses ~/.xinitrc if exists, otherwise uses /etc/X11/xinit/xinitrc.
  • /etc/X11/xinit/xinitrc sources /etc/X11/Xsession, that redirects output to .xsession-errors.
  • /etc/X11/Xsession sources ~/.xsessionrc if exists, then executes ~/.xsession if executable, sources if not.

What happens when using lightdm? If it doesn't source /etc/X11/Xsession, how could it possibly redirect errors to error-file ~/.xsession-errors (I couldn't find any informations on other scripts in /etc/X11/Xsession.d/)?

The man page for Xsession documents ~/.xsessionrc and ~/.xsession. It says that ~/.xsessionrc is only for setting variables and the ~/.xsession is for executing commands, but ~/.xsession gets sourced only if I create a custom *.desktop file in /usr/share/xsessions/ for it. Should I create a custom /etc/X11/Xsession.d/ file (like 40x11-common_xsessionrc works for ~/.xsessionrc), or just use ~/.xsessionrc to add any scripts?

Also, I'd like to know how x-window-manager and x-session-manager work through alternatives. I noticed that they seem to work if no ~/.xinitrc and ~/.xsession exist, and apparently they work only when running startx.

Thanks in advance for any answers.

Volker Siegel
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Giuseppe Di Chiacchio
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    By the way I'd have another question. Ubuntu's man suggests creating a custom *.desktop file in /usr/share/xsessions with line Exec=/etc/X11/Xsession in order to set custom settings in ~/.xsession. That means, running another wrapper after /usr/sbin/lightdm-session, which in this case would be /etc/X11/Xsession; that will result in everything under /etc/X11/Xsession.d/ being applied twice. So wouldn't it be better to create a script in /etc/X11/Xsession.d/ to source ~/.xsession? Any help appreciated. – Giuseppe Di Chiacchio Mar 24 '15 at 18:24
  • In order to use ~/.xsession through /usr/sbin/lightdm-session, it was useful to me creating a new script in /etc/X11/Xsession.d which I named 45x11-common_xsession. Since variables are all well defined into the wrapper, I just added the following lines: if [ -r "$USERXSESSION" ]; then . "$USERXSESSION" fi This way the wrapper will source ~/.xsession file too, after having sourced ~/.xsessionrc. Hope this might be useful. – Giuseppe Di Chiacchio Mar 26 '15 at 19:34
  • If you can answer part of your question, pleas just create an answer yourself, that's perfectly normal. The comments are only temporary ang can get lost. – Volker Siegel May 10 '15 at 08:37

1 Answers1

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This bug

Bug #1001035 “lightdm uses a hardcoded path to .xsession-errors,...” : Bugs : lightdm package : Ubuntu

states that LightDM has the path for $HOME/.xsession-errors hard-coded in its source. And that really should be configurable.

Sadly, “modern” display managers seem to often not care about /etc/X11 much anymore, and re-invent the wheel… badly.
Probably because it is rather hard to find out why things are the way they are. (I tried. I still don’t know why there are so many files/scripts and what all their purposes are.)

E.g. SDDM doesn’t use .xsession-errors at all, and logs to some other strange location, if at all.

Addendum

The second question should really be separate.
Due to me still not knowing all about it, I can’t help with that.
But I think I can say that you probably shouldn’t create another custom session file.
Maybe the LightDM documentation helps you there…

About the third question: The man page for xinit and its associated man pages (from the same software package) explain this. There’s a list of alternatives, some in $HOME, some in /etc, some even in /usr/share/… sub-directories. But I think if there is none, some default is assumed too.
Sorry, this should probably be separate too. I only post what I do know.

Evi1M4chine
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