From owner-freebsd-chat  Tue Oct 10 19:27:19 2000
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Date: Tue, 10 Oct 2000 19:27:10 -0700
From: "Crist J . Clark" <cjclark@reflexnet.net>
To: chat@freebsd.org
Subject: Self-DOS
Message-ID: <20001010192710.E25121@149.211.6.64.reflexcom.com>
Reply-To: cjclark@alum.mit.edu
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Here is a really fun way to DOS yourself. I wanted to run a process at
reduced priority in the background, so I did,

  # nice -20 program args &

At which point everything on the box just seemed to die. I got no
prompt back. I could do the username an password on vty's, but again,
no shell prompt would appear. A network login would establish the TCP
connection and just hang. I could ping, hellava lotta good that does
me.

I eventually realized what I had done. I was using /usr/bin/nice
syntax, but I had been in csh. In csh with its builtin nice, the above
is interpreted as run program at a nice of '-20,' that is at a
_rasied_ priority. I had effectively told the system to give the
program every single damn clock cycle.

The thing is, I ended up *cringe* hitting the reset button. I could
not find a way to get in there to kill the program. I crossed my
fingers (then uncrossed them) and did the three-finger M$ salute, but
that did not even do it (and it's not disabled). The box came up fine,
just a few extra seconds to do the fsck, but can anyone out there tell
me how I could have recovered from this without the drastic measures I
ended up taking?

Thanks. Oh, and don't laugh too hard. I can't be the first to have
done this.
-- 
Crist J. Clark                           cjclark@alum.mit.edu


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