[Pkg-xen-devel] how to get debugging output from dom0 kernel

[Ian Campbell]

On Sun, 2014-06-15 at 13:35 +0200, lee wrote:
> Ian Campbell <ijc at hellion.org.uk> writes:
> 
> > On Sun, 2014-06-15 at 11:03 +0200, lee wrote:
> >> Hi,
> >> 
> >> how could I get better debugging output from the dom0 kernel?
> >
> > Either configure a serial console [0] or add "noreboot" to your
> > *hypervisor* command line, so you can see (and perhaps
> > transcribe/photograph) the crash before manually rebooting.
> 
> The server isn't rebooting automatically, it only gets stuck.  I still
> have a monitor connected to it, so I can see what's printed to the
> console.  But the output is scrolled off screen by subsequent messages
> so that it's gone by the time I notice that it hangs.
> 
> If there was a way to disable the subsequent messages, I could take a
> picture.  Perhaps I can get output from a serial console if I manage to
> set that up ... or maybe I can actually make it crash instead of having
> to wait ...

Serial console would be best. I think the Linux kernel also has a panic
on crash option somewhere, perhaps oops=panic, but it depends rather
what form the initial error takes.

I suppose there are also various software monitoring solutions which
would alert you to something odd in the dom0 dmesg e.g. via email.

Ian.