Re: Configuring foreign packages without qemu in order to boot a system

+++ Paul Boddie [2012-09-02 01:07 +0200]:
> Hello,
> 
> I've recently been looking into using Emdebian on the Ben NanoNote, 
> 
> However, to get to this point, I have to rely on the existing OpenWrt 
> distribution to boot the device, log in, and then enter the Emdebian system 
> root using chroot in order to run "dpkg --configure -a". Once this has been 
> done, the device will boot into the Emdebian system.
> 
> This configuration step appears to be the necessary measure to permit the init 
> mechanism and various related activities to function. I suppose that not all 
> packages need to be configured, but some configuration seems to make the 
> difference between a functioning and non-functioning system.
>
> ...
>
> Obviously, in my situation, I can't boot into Emdebian without 
> having first performed the configuration step, so this supposedly leaves me 
> with the fairly undesirable option of using qemu.
> 
> I did wonder, however, whether there are any known techniques for configuring 
> just enough of a system on the build host so that the init mechanism can 
> complete its work on the target system and then allow the proper 
> configuration to occur. 

Multistrap provides a (fairly low-tech) mechanism for this. In your
multistrap config provide a
setupscript=/path/to/setup.sh
which does any tweaking necessary to make the image bootable (e.g. setting
/etc/fstab, inittab, /etc/modules to something useful).

> Alternatively, I wondered whether there might be any way of deploying a "first 
> boot" script to perform configuration on the target system.

That doesn't help if it won't even boot. So there is a second option:
configscript=/path/to/config.sh which specifies a script to copy into
the image for 'first run' use.

There are examples of these scripts in the package. Some details are
given in the 'Machine:variant support' and 'Root Filesystem
Configuration' sections of the multistrap man page. And also on
http://wiki.debian.org/Multistrap/CustomisingRootfs

> I see a script 
> apparently suggested for this kind of thing...
> 
> http://wiki.debian.org/Multistrap#Debconf_and_pre-seeding

That is a typical example of a first-run 'configscript'.

An alternative approach is to use the 'polystrap' wrapper, which uses
qemu to cross-configure the packages (after running multistrap) so
that the image has already had dpkg --configure -a run. This may or
not be easier/better depending on your circumstances and how closely
the qemu device resembles the one you are trying to configure for...

http://lists.debian.org/debian-embedded/2011/07/msg00019.html

> I would certainly appreciate any advice on this topic. Emdebian promises to 
> make a lot of things easier when developing for embedded devices like the 
> NanoNote - just the availability of numerous packages for different 
> architectures is a real time-saver - and I'd like to be able to offer some 
> concrete documentation to help people start using it without there being too 
> many complications involved.

HTH

Wookey
-- 
Principal hats:  Linaro, Emdebian, Wookware, Balloonboard, ARM
http://wookware.org/