After upgrading to debian jessie my dated desktop system no longer powers off reliably (/sbin/poweroff - via systemctl on tty1). Instead, it shuts down, pauses and reboots and only powers off if I press the power-button. I tried various recommendations like
acpi=force playing with bios settings, adding nouveau.modeset=0 and many more.
The only thing I found so far, is that not starting a graphical session seems to "fix" the problem. My Xsession is a simple
.xsession file, there is no session manager involved (afaik) and all I do is start a number of programs. When I strip this file down to just an
xterm or I do not log in at all, the system powers down.
I tried to uncomment more programs in my .xsession file in the hope of finding a culprit, but this did not lead to a conclusion. There seems to be some randomness involved. I am sure than none of my programs are still runnig at the time I issue the poweroff because I kill them all (uncluding a user systemd which was started by I-dont-know-who)
In the last messages before it reboots I see
System wakeup enabled by ACPI Preparing to enter systel sleep state 5 GPU lockup - switching to software fbcon
But I see the same messages when it does poweroff (not 100% sure, because they are visible only for a short moment then)
Also I notice that in the bad cases, there are long pauses in the shutdown process, e.g. after
Stopping target network there is like a 2-minute pause and I don't know what the system is waiting for.
What I am after is a way to diagnose the problem, rather than shooting at the moon.
- How can I find out what the system is waiting for in those long pauses
- Or more generally: how can I get more information about what's going on during shutdown, is there a "shutdown log"?
- How is acpi involved in the shutdown process and how can I find out why it is doing what it is doing?