Kernel dumps [was Re: possible changes from Panzura]

[Lars Engels]

On Wed, Jul 10, 2013 at 02:04:17PM -0600, asomers at gmail.com wrote:
> On Wed, Jul 10, 2013 at 12:57 PM, Jordan Hubbard <jkh at mail.turbofuzz.com> wrote:
> >
> > On Jul 10, 2013, at 11:16 AM, Julian Elischer <julian at elischer.org> wrote:
> >
> >> My first  candidates are:
> >
> > Those sound useful.   Just out of curiosity, however, since we're on
> > the topic of kernel dumps:  Has anyone even looked into the notion
> > of an emergency fall-back network stack to enable remote kernel
> > panic (or system hang) debugging, the way OS X lets you do?  I can't
> > tell you the number of times I've NMI'd a Mac and connected to it
> > remotely in a scenario where everything was totally wedged and just
> > a couple of minutes in kgdb (or now lldb) quickly showed that
> > everything was waiting on a specific lock and the problem became
> > manifestly clear.
> >
> > The feature also lets you scrape a panic'd machine with automation,
> > running some kgdb scripts against it to glean useful information for
> > later analysis vs having to have someone schlep the dump image
> > manually to triage.  It's going to be damn hard to live without this
> > now, and if someone else isn't working on it, that's good to know
> > too!
> 
> I don't doubt that it would be useful to have an emergency network
> stack.  But have you ever looked into debugging over firewire?  We've
> had success with it.  All of our development machines are connected to
> a single firewire bus.  When one panics, we can remotely debug it with
> both kdb and ddb.  It's not ethernet , but it's still much faster than
> a serial port.
> https://wiki.freebsd.org/DebugWithDcons

Debugging over Firewire may be very nice to use, but Firewire is dead
while every single device nowadays has a network interface, admittedly
it's often wireless.
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