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List:       busybox
Subject:    Re: The '-/bin/sh' permanently restarts
From:       Detlef Vollmann <dv () vollmann ! ch>
Date:       2009-10-31 23:52:56
Message-ID: 4AECCDD8.2070407 () vollmann ! ch
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Mike Frysinger wrote:
> On Saturday 31 October 2009 13:53:37 Detlef Vollmann wrote:
>> Bernhard Reutner-Fischer wrote:
>>> On Sat, Oct 31, 2009 at 10:48:51AM +0100, Bernhard Reutner-Fischer wrote:
[starting a shell for debugging only]

>>> i.e. you listen for some kind of trigger and eventually toggle the debug
>>> getty. Whether that trigger comes in via some keyboard-sequence, net port
>>> 80/443/22/23, token in nvram, phase of the moon is OT for this list, imo.
>> No we're back where we started: the trigger is the 'console=' kernel
>> argument.  It can't change at runtime, but only when powered off.
>> And it must be detected by the bootloader anyway, because then the
>> bootloader will use the console as well.
> 
> you're correct that we're back where we started, but not the place you think.  
> your trigger method (console=) is severely limited (as you've already found 
> out).  pick a different trigger method (as Bernhard suggested).
Well, the trigger is the existence of a serial port.
If we use additional logic in Linux userspace to detect that hardware,
we have to change two different pieces of code if the hardware changes.
And as the Linux kernel needs that kernel argument anyway to produce
boot messages for the debugging case, it makes sense to use exactly
that to decide whether to start a shell on that console.
And though the kernel argument limits the options to start a shell,
earlier messages have provided two ways how we achieve that
('console=tty1' and the original inittab entry or a script with the
'tty' command to check for the console), and I appreciate that.
Unfortunately, Bernhard's proposal is not so useful for us.
YMMV.

> nothing you've highlighted so far is a bug in busybox.  just your 
> implementation/expectations.
I agree.

   Detlef

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