From owner-freebsd-current  Tue Jul 20 12: 3:34 1999
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From: "Steven G. Kargl" <kargl@troutmask.apl.washington.edu>
Message-Id: <199907201906.MAA04538@troutmask.apl.washington.edu>
Subject: Re: is dumpon/savecore broken?
In-Reply-To: <199907201849.LAA06381@apollo.backplane.com> from Matthew Dillon at "Jul 20, 1999 11:49:50 am"
To: dillon@apollo.backplane.com (Matthew Dillon)
Date: Tue, 20 Jul 1999 12:06:26 -0700 (PDT)
Cc: phk@critter.freebsd.dk (Poul-Henning Kamp),
	freebsd-current@FreeBSD.ORG
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According to Matthew Dillon:
> :> >   dumpon: crash dumps to /dev/da0s1b (4, 131073)
> :> >   checking for core dump...savecore: can't find device 13/131073
> :> 
> :> >It seems that the the major device number is reset from 4 to 13.
> :> 
> :> Yes, all dev_t's which make it out of the kernel have cmajor
> :> numbers now.
> :> 
> :> Try this change to savecore:
> :> 
> :> 	/ddname = find_dev/s/BLK/CHR/
> :> 
> :
> :Thanks, Poul. 
> :
> :I forgot to mention that this is after a "make world" and new kernel
> :from today (1000 PST).
> :
> 
>     A checklist for people who want kernel cores:
> 

[Matt's check list deleted which I meet]

>       /var/crash must nominally have sufficient space to hold the crash
>       dump (a file of the same size as the amount of memory you have),
>       *and* the kernel image.  Normally you give it a lot more space so
>       you store several crash dumps in it at once.

Matt,

AFAICT, the problem is due to the translation of /dev/da0s1b to
major and minor numbers.  dumpon takes /dev/da0s1b and translates
it to (4,131073) in my case.  savecore uses sysctl kern.dumpdev to
determine the dump device.  kern.dumpdev is set to (13,131073).
Thus, dumpon uses bmajor and savecore uses cmajor device numbers.

I also note that savecore grovels around in /dev/kmem which scares
the heck out of me as far as my hacking abilities go ;-)

-- 
Steve


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