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Date: Tue, 20 Jun 2006 10:02:23 +1000
Subject: Re: emergency or init=/bin/sh mode and terminal signals
From: David Luyer <david@luyer.net>
To: Samuel Thibault <samuel.thibault@ens-lyon.org>,
       "linux-os (Dick Johnson)" <linux-os@analogic.com>
CC: <linux-kernel@vger.kernel.org>
Message-ID: <C0BD782F.CF80%david@luyer.net>
Thread-Topic: emergency or init=/bin/sh mode and terminal signals
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On 20/6/06 8:09 AM, "Samuel Thibault" <samuel.thibault@ens-lyon.org> wrote:
> linux-os (Dick Johnson), le Mon 19 Jun 2006 07:37:02 -0400, a écrit :
>> You can't allow some terminal input to affect init. It has been the
>> de facto standard in Unix, that the only time one should have a
>> controlling terminal is after somebody logs in and owns something to
>> control.
> 
> Ok. The following still makes sense, doesn't it? (i.e. set a session for
> the emergency shell)
> 
> --- linux-2.6.17-orig/init/main.c 2006-06-18 19:22:40.000000000 +0200
> +++ linux-2.6.17-perso/init/main.c 2006-06-20 00:07:07.000000000 +0200
> @@ -729,6 +729,11 @@
> run_init_process("/sbin/init");
> run_init_process("/etc/init");
> run_init_process("/bin/init");
> +
> + /* Set a session for the shell.  */
> + sys_setsid();
> + sys_ioctl(0, TIOCSCTTY, 1);
> +
> run_init_process("/bin/sh");
>  
> panic("No init found.  Try passing init= option to kernel.");

What if people are booting via /bin/sh and then setting up
their custom chroot's and init(s), and don't want these init(s) to
be part of a session?

It is also particularly possible for an embedded system to start
up via /bin/sh running /etc/profile rather than using an init type
program.

Also, the above doesn't help people specifying "init=/bin/sh" on the
command line (as per the original post subject).  The real solution
is for them to specify a different init= or run/exec something to set
up their tty and session once logged in.

David.