can't get a crash dump

[Roberto Nunnari]

Hi.

A couple of days ago I upgrades a few ports on
a 5.3 box and since then I'm often getting crashes.

-bash-2.05b# uname -a
FreeBSD jupiter.noonlights.net 5.3-RELEASE-p5 FreeBSD 5.3-RELEASE-p5 #0: 
Wed Feb 16 23:36:03 CET 2005 
root at jupiter.noonlights.net:/usr/obj/usr/src/sys/JUPITER  i386


I'd like to get a crash dump and so
I added the following lines to /etc/rc.conf
dumpdev="/dev/ad0s1b"
dumpdir="/usr/crash"

-bash-2.05b# swapinfo
Device          1K-blocks     Used    Avail Capacity
/dev/ad0s1b        503360        0   503360     0%


-bash-2.05b# ls -ld /usr/crash/
drwx------  2 root  wheel  512 Feb 16 11:17 /usr/crash/

the machine only has 256MB RAM and the filesystem has over
5 GB free,
but I'm not getting any dump! /usr/crash/ is always empty.

..and the machine crashes quite often:
-bash-2.05b# last|grep reboot
reboot           ~                         Thu Feb 17 07:58
reboot           ~                         Thu Feb 17 01:23
reboot           ~                         Wed Feb 16 22:48
reboot           ~                         Wed Feb 16 21:59
reboot           ~                         Wed Feb 16 21:37
reboot           ~                         Wed Feb 16 21:08
reboot           ~                         Wed Feb 16 20:56
reboot           ~                         Wed Feb 16 20:44
reboot           ~                         Wed Feb 16 20:20
reboot           ~                         Wed Feb 16 20:04
reboot           ~                         Wed Feb 16 19:17
reboot           ~                         Wed Feb 16 18:40
reboot           ~                         Wed Feb 16 17:26
reboot           ~                         Wed Feb 16 14:07
reboot           ~                         Wed Feb 16 12:39
reboot           ~                         Wed Feb 16 11:30
reboot           ~                         Wed Feb 16 10:27
reboot           ~                         Wed Feb 16 09:31
reboot           ~                         Wed Feb 16 09:16
reboot           ~                         Mon Feb 14 14:11
reboot           ~                         Sun Feb 13 23:49
reboot           ~                         Sun Feb 13 22:33
reboot           ~                         Sun Feb 13 12:22


What do I miss? Do I need some kernel option to get a crash
dump?

Best regards.
-- 
               Roberto Nunnari -software engineer-
                mailto:roberto.nunnari at supsi.ch
  Scuola Universitaria Professionale della Svizzera Italiana
              Dipartimento Tecnologie Innovative
                   http://www.dti.supsi.ch
  SUPSI-DTI
  Via Cantonale                        tel: +41-91-6108561
  6928 Manno                 """       fax: +41-91-6108570
  Switzerland               (o o)
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