*BSD News Article 14569


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Newsgroups: comp.os.386bsd.development
From: damian@centrix.demon.co.uk (damian)
Subject: Re: SIGKILL and kill
References: <1qo3mq$d4b@news.cs.tu-berlin.de>
Organization: Centrix
Keywords: SIGNALS SECURITY
Date: Sat, 17 Apr 1993 10:54:03 +0000
Message-ID: <9304171535.ab08751@gate.demon.co.uk>
Sender: usenet@demon.co.uk
Lines: 36

In article <1qo3mq$d4b@news.cs.tu-berlin.de> klier@cs.tu-berlin.de (Jan Klier) writes:

[ Restricting kill -9 to superuser only ]

I agree with the problem, though your solution is a bit draconian.
It somewhat turns off the rather nice 'you asked for it, you got it' unix
mentality.

I am not sure that 386bsd is the right enviroment to test the idea. Most
people who use 386bsd know what they are doing. You really want a commercial
unix to try it on (with real non-techie users), I guess for testing you
could just replace kill with your own program.

kill -9 is often used without even trying a normal kill (kill -15),
I know of several bits of software that like to clean up locks, clean up
data files, flush buffers etc etc. Allowing only superuser to send a SIGKILL
might break some software, but not much.

[ FLAME ON ]

I think unfortunately the main problem is that a large amount amount of
commercial software (particularly 'DOS ports') simply ignore SIGTERM (15).
I think this is criminal, no software should ignore SIGTERM, since as we
have seen a SIGKILL will soon follow. In fact I have been trying to
work out why sh ignores SIGTERM when at the command prompt (it behaves
properly when running a script).

[ FLAME OFF ]

Damian
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