[Ti] powerbook crashing [panic.log]

[Kynan Shook]

Well, in theory, they should all get logged, but I have seen them get  
missed myself, and I'm not always sure why.

In 10.2, when they changed from the behavior of dumping ugly text all  
over your screen to putting up a multi-lingual message, they  
redirected the text to the PRAM.  Then, the next time you reboot, the  
OS sees that there is a panic log in the PRAM, and writes it to  
disk.  It's done this way because writing to the PRAM is a more basic  
access; once the kernel has panicked, there is no guarantee that the  
OS is in a state where it would be possible to write to the disk.

There are two reasons why a panic won't be logged.  The first is if  
you have turned on remote debugging in Open Firmware - this is used  
by people who write kernel code.  Once the kernel panics, they can  
use a second computer to tap into memory and the kernel and see what  
went wrong.  You would almost certainly know if you had turned this  
on.  If you think you might've turned it on, type "nvram boot-args"  
on the command line; if it prints out just "boot-args", it's off.  If  
it prints anything after "boot-args", then you have a non-standard  
setup - specifically, if it spits out "debug=0x(something)", then it  
won't save a panic log.

The other time it won't save the panic log is if you reset PRAM.  One  
could do this inadvertently by using the button on the back of  
certain TiBooks, under the keyboard of others, or by pressing a  
certain key combo.  To properly reboot a panicked Mac, you should  
either press Command-Control-Power or hold down the power button for  
several seconds.

Now, I know I've had logs not saved when neither of these is the case  
- of course, if the computer panics while booting, before it can  
write to the log, the old panic will get overwritten.  Also, I  
believe the information is only saved for 1 reboot, so if you boot  
into Single User Mode, boot to a CD, or something else immediately  
after the panic, you may lose the log.  However, I don't know what  
else causes it to miss some panics.  Perhaps changed permissions  
somewhere, I suppose.  Or maybe the kernel is in really bad shape,  
and can't even manage to write to PRAM.

If all else fails and you want to see your panic, it's also possible  
to disable the graphical panic display, and go back to the text on  
your screen.

HTH,

On Mar 22, 2006, at 12:27 PM, Dr Trevor J. Hutley wrote:
>
> On 22 Mar 2006, at 20:49, Kynan Shook wrote:
>
>> What do you see in the file /Library/Logs/panic.log?
>
> Kynan - since I have occasional kernel panics, (i had one this  
> afternoon), I was interested to read about this panic.log (which I  
> never knew about).
> When I open mine, the last entry is in mid-Feb, which is strange,  
> as I must have 10 panics since then, including the one I just  
> mentioned.
> Does that mean that they are not all logged?
>
> Trevor
>
>