[mythtv-users] Random system freezes -- clueless

[Stephen Worthington]

On Thu, 17 Dec 2015 18:31:02 -0600, you wrote:

>My Myth system has a bad habit of freezing, except when I'm doing something
>on it.  It will automatically wake up to record something and shutdown once
>it is finished and everything works.  But sometimes... The system just
>stops in its tracks, like it hit a halt instruction.  There are no errors
>reported in any of the log files in /var/log, /var/log/lightdm,
>/var/log/upstart, /var/log/mysql, or /var/log/mythtv.  They just stop dead
>in their tracks and I have to hit the reset button or cycle the power to
>get it going again.  Not even installing the watchdog package and
>configuring it rescues the system.  I get lots of watchdog check messages
>in the logs right up until the system freezes in its tracks at some random
>time hours or days after the last incident.  I've run memtest for hours
>with no problems reported -- like overnight plus half the next day.  I've
>run disk diagnostics and swapped disks (within limits).  I've tried most
>things I found on my copy of the Ultimate Boot CD.  All to say I've found
>no smoking gun.  So, like I said, I'm clueless.  I've ordered a different
>motherboard, but I'm only shooting in the dark with that.
>
>Anyone have something better than a wild guess about what's going on?

I presume that it is freezing while on, rather than just failing to
startup again at the scheduled time.

What is the operating system?

Do any of the magic SysReq keys still work?

  https://en.wikipedia.org/wiki/Magic_SysRq_key

If your motherboard has a serial port and you have something you can
plug into that (eg a laptop and a serial to USB converter), then that
is the place to get last ditch error messages if any are happening.
But you have to have the monitoring PC or terminal attached at the
time the error happens.

It is always worthwhile just pulling out all the cards and reseating
them - the connectors can get dirty, or the cards move a bit with age.
Especially if they do not fit well in their slots in the first place,
as does happen with some cards.

The next thing I always suspect is the power supply.  If you have
another one you can swap with that power supply, try it for a few days
and see.  I always keep a spare power supply for my PCs as I have had
power supplies just die without notice.  But they can sometimes do
some very strange things without having any visible indications short
of using an oscilloscope.