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Date:      Fri, 1 Dec 2006 15:21:43 -0500
From:      Kris Kennaway <kris@obsecurity.org>
To:        Cheng Jin <chengjin@cs.caltech.edu>
Cc:        freebsd-questions@freebsd.org
Subject:   Re: 5.4 kernel crashdump not consistently working
Message-ID:  <20061201202143.GA27869@xor.obsecurity.org>
In-Reply-To: <Pine.LNX.4.60.0612011137080.14849@orchestra.cs.caltech.edu>
References:  <Pine.LNX.4.60.0612011137080.14849@orchestra.cs.caltech.edu>

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On Fri, Dec 01, 2006 at 11:48:06AM -0800, Cheng Jin wrote:
> hi,
>=20
> i have run into this strange problem of kernel crashdump not
> working consistently under FreeBSd 5.4.  we have bunch of development
> machines with identical physical configurations, and every one of
> them is setup to save the vmcore after a panic.  The difference
> as far as i could tell is the FreeBSD 5.4 version, which=20
> different people installed using different methods, CD, network, CVS...
>=20
> I followed the instructions found on the official FreeBSD site
> as far as i could tell.
>=20
> including in the kernel config file the following options
>=20
> options DDB
> options KDB
> options GDB
> options KDB_UNATTENDED
>=20
> include in the /etc/rc.conf file
>=20
> dumpdev=3D"/dev/ad0s1b" # 2GB swap partition with 1GB of physical memory
> dumpdir=3D"/usr/crash"  #
>=20
> and making sure the dir exists
>=20
> crashdump works on some of these machines, but not on others, and
> on those that don't work, i just see
>=20
> Dumping 1014MB
>=20
> and the system just sits there.  I added a printf line into the
> dumpsys function, and it seems that it just loops without ever
> writing anything to disk. for those that are curious about the
> details, the variables "i", "mb" are always just zero, "count goes
> up everytime i press a key, and "va" stays at the same memory
> address, and left never decreases.
>=20
> Comments would be greatly appreciated.

Some disk drivers seem to have problems dumping (each driver has its
own dump routine so there is scope for bugs especially on less
commonly used devices).  Try a later version of FreeBSD, e.g. 6.1 or
6.2.

Kris

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