The '-/bin/sh' permanently restarts

Mike Frysinger vapier at gentoo.org
Sat Oct 31 19:59:04 UTC 2009


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:
> >> On Fri, Oct 30, 2009 at 11:56:13PM +0100, Detlef Vollmann wrote:
> >>> Mike Frysinger wrote:
> >>>> On Thursday 29 October 2009 16:06:54 Detlef Vollmann wrote:
> >>>>> Bernhard Reutner-Fischer wrote:
> >>>>>> I suggest you just run a sh on e.g. ttyS0 if you're debugging and
> >>>>>> turn it off if you're not. My favourite link as a stub:
> >>>>>> http://repo.or.cz/w/buildroot.git?a=blob_plain;f=target/generic/targ
> >>>>>>et_bu sybox_skeleton/etc/inittab;hb=HEAD
> >>>>>
> >>>>> Sorry, I'm probably missing something:
> >>>>> How do you start the shell if you don't have a shell?
> >>>>> This looks to me like a hen-and-egg problem.
> >>>>
> >>>> shell's arent init / process managers.  use init.
> >>>
> >>> Exactly.
> >>> My point was: if I don't start a shell by inittab (because I only
> >>> want it for debugging), then I can't start a shell later...
> >>
> >> huh?
> >> sed -i -e "/^#ttyS0/s/^[#]*//" /etc/inittab && kill -HUP 1
> >
> > 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).

nothing you've highlighted so far is a bug in busybox.  just your 
implementation/expectations.
-mike
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