Hi QiZhi,

Following the reboot are there any relevant messages in /var/log/syslog?

Also are you using Nautilus as a file manager? I was having a similar issue recently and was getting lots of:
org.gnome.Nautilus[1027]: Failed to open VDPAU backend libvdpau_i965.so: cannot open shared object file: No such file or directory
I chose to remove Nautilus and haven't had a problem since. Possibly related to this existing upstream bug

@krisgesling Can you elaborate why Nautilus would be the culprit here?

Short answer, I was wrong...

I was investigating a similar issue. Whole computer freezing whilst using VLC in fullscreen mode. audio would loop over a short 1ish second loop.
When I checked /var/log/syslog I was seeing heaps of the VDPAU errors attributed to nautilus just before the reboot. So I uninstalled nautilus to see if it was causing the reboots and it stopped rebooting... for a period of time.

Unfortunately it's still rebooting randomly whilst using VLC in fullscreen mode. It always seems to be when I pause, enter fullscreen, or some other action - not in the middle of just playing a video. Nautilus is still uninstalled so clearly not the culprit :(

Not sure what other logs to check or other action to diagnose. Any suggestions?

@krisgesling This sounds like a lower-level issue, either in your graphics driver or there is a problem with your hardware. (Given you are playing video, it could be overheating, just as one example.) Can you briefly outline your hardware? Thanks.

It's a Librem 15v2.

It does get pretty warm, and I live in far northern Australia which is just generally hot and doesn't help things.

@krisgesling If it's doing this after watching video for a while, this might be the case. Otherwise it's likely some kind of BIOS/video card/blah interaction. Can you speak to the timings here? It could also be faulty RAM, etc. etc. :)

(I cannot reproduce this, alas!)

I ran MemTest86 v7.4 through the default 4 tests and it returned no errors.

I think I'm due for a fresh OS install, will see if it returns after that.

Thanks @krisgesling. Let me know either way.

Having no problem regarding to heat or warm area, my problem was solved with the last update of VLC.
Thx for your concern.