Remounting a drive as read/write crashes the system and no dmesg.boot

[Scott Schappell]

On 8/20/2009 4:31 PM, Mel Flynn wrote:
>
> http://www.freebsd.org/doc/en_US.ISO8859-1/books/developers-handbook/kerneldebug.html

OK, /backup was mounted read only, I did the following

umount /backup
mount -o rw /backup
[root at arthur ~]# dd if=/dev/zero of=/backup/testfile bs=1024
dd: /backup/testfile: end of device
21122+0 records in
21121+0 records out
21627904 bytes transferred in 2.215991 secs (9759924 bytes/sec)
[root at arthur ~]#


You can see by that snippet it barfed at 21627094 bytes (21 megabytes, 
ish). /backup has 100s of GiB free.

Filesystem     Size    Used   Avail Capacity  Mounted on
/dev/ad0s1a    9.7G    453M    8.5G     5%    /
devfs          1.0K    1.0K      0B   100%    /dev
/dev/ad0s1d     15G    481M     13G     4%    /var
/dev/ad0s1e     15G    3.1G     10G    23%    /usr
/dev/ad0s1f     15G    1.4G     12G    10%    /usr/local
/dev/ad0s1g    216G    3.5G    195G     2%    /home
/dev/ad2s1d    226G     32G    176G    15%    /backup

I cannot get the system to generate a dump, even though dumpon verified 
it's set to the swap drive but /var/crash stays empty. I have 
dumpdev=AUTO in rc.conf and dumpdir=/var/crash as well.

Could this have anything to do with how I added the drive? I followed 
the handbook instructions but maybe I messed it up.