Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262599AbVDGUvn (ORCPT ); Thu, 7 Apr 2005 16:51:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262597AbVDGUvm (ORCPT ); Thu, 7 Apr 2005 16:51:42 -0400 Received: from alog0057.analogic.com ([208.224.220.72]:4838 "EHLO chaos.analogic.com") by vger.kernel.org with ESMTP id S262599AbVDGUvT (ORCPT ); Thu, 7 Apr 2005 16:51:19 -0400 Date: Thu, 7 Apr 2005 16:50:32 -0400 (EDT) From: "Richard B. Johnson" Reply-To: linux-os@analogic.com To: Jan Harkes cc: Linux kernel Subject: Re: Linux-2.6.11 can't disable CAD In-Reply-To: <20050407202059.GA414@delft.aura.cs.cmu.edu> Message-ID: References: <20050407202059.GA414@delft.aura.cs.cmu.edu> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2165 Lines: 56 On Thu, 7 Apr 2005, Jan Harkes wrote: > On Thu, Apr 07, 2005 at 11:16:14AM -0400, Richard B. Johnson wrote: >> In the not-too distant past, one could disable Ctl-Alt-DEL. >> Can't do it anymore. > ... >> Observe that reboot() returns 0 and `strace` understands what >> parameters were passed. The result is that, if I hit Ctl-Alt-Del, >> `init` will still execute the shutdown-order (INIT 0). > > Actually, if CAD is enabled in the kernel, it will just reboot. > If CAD is disabled in the kernel a SIGINT is sent to pid 1 (/sbin/init). > No, that's not how it ever worked. There are parameters that are available in the reboot-system call that define the operation that will occur when the 3-finger salute occurs. Execute man 2 reboot. > So what you probably had in the not-too-distant past was a disabled CAD > in the kernel _and_ you had modified the following line in /etc/inittab, > The systems to which I refer do not, and never even had a file-system, much-less any inittab. That's SYS-V init stuff for interactive access. > # What to do when CTRL-ALT-DEL is pressed. > ca:12345:ctrlaltdel:/sbin/shutdown -t1 -a -r now > > AFAIK this hasn't ever really changed. > > Jan > The kernel's response (or the 'C' runtime-library interface) has changed so that it is now possible for somebody at the keyboard of a machine to destroy the machine's operation by executing Ctl-Alt-Del. I don't know how long this potential catastrophe has existed, but when the machine(s) were initially certified there was no possible way for a user to kill the machine from the keyboard. It is possible that a 'C' runtime library was changed in the tarket so it's not a kernel problem. I'm checking it out now. Cheers, Dick Johnson Penguin : Linux version 2.6.11 on an i686 machine (5537.79 BogoMips). Notice : All mail here is now cached for review by Dictator Bush. 98.36% of all statistics are fiction. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/