[mythtvnz] Bit rot?

[Steve Hodge]

On Fri, Jun 27, 2008 at 2:19 PM, Michael Dilger <mike at mikedilger.com> wrote:

> AlanP wrote:
> > Every three or four months, my mythbox goes belly up. It works if I reset
> > it -- for about twenty minutes, then it locks up. Hard. Reinstalling it
> and
> > rescueing my settings from the backup (go go Knoppmyth!) usually seems to
> > fix it.
> >
> If reinstalling fixes it, then it is probably file system damage.   If
> you get hard hangs and have to press the power button, that does file
> system damage each time.
>

But not normally damage to executables or other read only data files. Actual
file damage is pretty unusual for a hardware fault - it's usually a symptom
of a virus or otherwise compromised system.


> You could verify this by running fsck on your root partition by booting
> of CD first.
>
> fsck can fix the structure of the file system, but damaged files
> typically remain damaged and "bit rot" continues.  There are ways to use
> backups and rsync or cpio to determine what has "rotted" and spot-fix
> those changes.
>
> To see what hardware is causing the crashes, leave your system on the
> console (if in X, press ctrl-alt-F1) and turn off screen blanking on
> that terminal (setterm -blank 0 -powersave off), then leave it alone
> until it hangs.   If you have it compiling something big and nasty on
> another terminal, that could help set off a freeze event.   It should
> print out a nice machine check exception error message something like this:
>
>    CPU0: Machine Check Exception 000000000000004
>    Kernel Panic - not syncing: CPU Context Corrupt
>
> Then you can run that message through a program called mcelog (you may
> have to install that) to get more information on what the message
> means... it may for instance tell you which subcomponent of your
> computer failed.... most likely some piece of the motherboard you cannot
> replace, or memory... but interesting none-the-less.
>
> Practically, the solution is what others have mentioned:  blow off the
> dust with an air compressor,  upgrade your fans (if you use quiet fans,
> sorry, get loud fans),  down-tweak your BIOS settings (underclock
> things, increase memory timing), and pray that this will be enough.   If
> not, start overvolting as well ... overvolting wears things down faster,
> and creates more heat, but does bring stability.
>
> If you still get hard crashes, you will still get "bit rot" and the only
> solution then is to get a new computer.
>

All good advice. One thing you didn't mention that is often at fault is the
power supply. The current supply might not be able to handle the load or it
might be overheating or contributing to a heat problem elsewhere. I'd
consider replacing that before chucking the whole machine away.

Also - take a look at the capacitors on the motherboard. If the tops are
bulging then the motherboard is stuffed.

Cheers,
Steve
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