I'm running my 486 headless, and now twice in as many days I've gotten
the following behaviour: I telnet in to the 486, and it reboots.

After the reboot, I can telnet in fine:

porter% uptime
 9:05AM  up 2 mins, 1 user, load averages: 0.61, 0.25, 0.10
porter% last | head
george    ttyp0    172.16.0.7       Thu Apr  2 09:05   still logged in
reboot    ~                         Thu Apr  2 09:05
george    ttyp1    172.16.0.9       Wed Apr  1 21:57 - 21:59  (00:01)
george    ttyp0    172.16.0.9       Wed Apr  1 21:49 - 21:58  (00:09)
...

It appears to be a clean reboot. The only thing interesting in
/var/log/messages are messages of this form:

Apr  1 00:00:05 porter syslogd: restart
Apr  1 15:00:01 porter syslogd: restart
Apr  1 19:00:01 porter syslogd: restart
Apr  1 21:48:33 porter syslogd: restart
Apr  2 09:04:57 porter syslogd: restart

Although there are several such messages, only two actual reboots have
occurred. For example, for the 'restarts' occurring on Apr 1, I wasn't
even home for three of them, then I got home, telnetted in, and it
rebooted.

Misc odd things from my /var/log/messages:
Apr  1 23:00:11 porter /netbsd: wdc1(0): lost interrupt
Apr  1 23:00:11 porter /netbsd:         type: ata
Apr  1 23:00:11 porter /netbsd:         c_bcount: 4096
Apr  1 23:00:11 porter /netbsd:         c_skip: 0
Apr  1 23:00:12 porter /netbsd: wd1: wdcintr: read intr before drq
Apr  1 23:07:11 porter /netbsd: uid 101 on /: file system full
Apr  1 23:18:56 porter /netbsd: wdc1(0): lost interrupt
Apr  1 23:18:57 porter /netbsd:         type: ata
Apr  1 23:18:57 porter /netbsd:         c_bcount: 4096
Apr  1 23:18:57 porter /netbsd:         c_skip: 0
Apr  1 23:18:57 porter /netbsd: wd1: wdcintr: read intr before drq
...
Apr  2 09:05:02 porter /netbsd: root on wd0a dumps on wd0b
Mar 31 21:55:27 porter savecore: /dev/wd0b: Device not configured
..

wd0 is a 400M drive (/ on wd0a, /usr on wd0e), and wd1 is a 40M drive I
use for swap (wd1b).

Does any of this add up ?

TIA.

-- 
George L. Coulouris - http://www.tc.cornell.edu/~glc5/
NetBSD 1.3 - free, multiplatform unix. http://www.netbsd.org/