Not-Booting Kernel Question

[Frank Murphy]

If a kernel update cause boot-failure, *314*
how does one retrieve useful info dmesg etc..


Frank


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[Tom Horsley]

On Tue, 09 Sep 2008 11:51:47 +0100
Frank Murphy <frankly3d(a)gmail.com&gt; wrote:

>  If a kernel update cause boot-failure, *314*
>  how does one retrieve useful info dmesg etc.. 
If you just want to dig up log files, you can always boot
from DVD in rescue mode and mount the filesystems and poke
around to see whats there (or boot a live CD and do the
same).

Unfortunately, some information doesn't seem to go anywhere
other than the console (things like kernel walkback traces).
I've only ever been able to capture them by rigging up a 2nd
computer with a null modem cable and booting the first with
serial console setup on kernel boot options.

If there is something more convenient than using a serial
console to capture everything that happens during boot, I'd
love to find out how to do it :-).

[Frank Murphy]

On Tue, 2008-09-09 at 07:36 -0400, Tom Horsley wrote:
>  On Tue, 09 Sep 2008 11:51:47 +0100
>  Frank Murphy <frankly3d(a)gmail.com&gt; wrote:
>  
>  Unfortunately, some information doesn't seem to go anywhere
>  other than the console (things like kernel walkback traces).
>  I've only ever been able to capture them by rigging up a 2nd
>  computer with a null modem cable and booting the first with
>  serial console setup on kernel boot options. 
How could I manage this with a laptop and desktop (kernel probs)
and the laptop only has usb connectors?

Frank

[Michal Jaegermann]

On Tue, Sep 09, 2008 at 01:06:56PM +0100, Frank Murphy wrote:
>  On Tue, 2008-09-09 at 07:36 -0400, Tom Horsley wrote:
>  > I've only ever been able to capture them by rigging up a 2nd
>  > computer with a null modem cable and booting the first with
>  > serial console setup on kernel boot options.
>  
>  How could I manage this with a laptop and desktop (kernel probs)
>  and the laptop only has usb connectors? 
There is also netconsole.  Check how to set that up
in Documentation/networking/netconsole.txt from a kernel-doc
package.  Depending on where you are crashing this may kick
in too late, though.

There exist also serial adapters for USB but I never used
one and have no idea how much of a system you have to have
running before one will start to function.

The real serial console is hard to beat for your purposes
but that hardware is unfortunately getting extinct.

   Michal