HACKING

====================
RescueOS build HOWTO

  These instructions are for folks who want to modify RescueOS and make their
  own images.  If you just want to use RescueOS on your N900, you'll want to
  get one of the prebuilt images and look at 'documentation.txt' for usage
  info.

RescueOS images are modified buildroot images.  This source distribution is
just a collection of config files, patches, etc. that configure and customize
buildroot builds.

You'll need a GNU/Linux system to host the build.  You'll need 'git' and
'quilt' to checkout the RescueOS source and apply our buildroot patches,
respectively.  Once that's done, you'll also need to satisfy buildroot's
prerequisites; we'll address that later.

These files are meant to be used with version 2013.02 of buildroot.  (Ports to
newer versions are welcome.)

Start by unpacking the RescueOS and buildroot sources into separate
directories.  We recommend putting the two directories next to each other under
a common parent directory:

  $ mkdir rescueos-build
  $ cd rescueos-build

Use git to checkout the RescueOS source.  It will go into a subdirectory named
'N900_RescueOS'.

  $ git clone <rescueos repository url>

Fetch, verify, and unpack the buildroot source.    It will end up in a
subdirectory named 'buildroot-2013.02'.

  $ wget http://www.buildroot.org/downloads/buildroot-2013.02.tar.bz2
  $ wget http://www.buildroot.org/downloads/buildroot-2013.02.tar.bz2.sign
  $ gpg --recv-keys B025BA8B59C36319
  $ gpg --verify buildroot-2013.02.tar.bz2.sign
  $ compare the checksums in buildroot-2013.02.tar.bz2.sign with the actual checksums of buildroot-2013.02.tar.bz2 (it's not a detached signature)
  $ tar --extract --bzip --file buildroot-2013.02.tar.bz2

Buildroot's prerequisites are documented in the "System requirements" section
of the buildroot manual ('buildroot-2013.02/docs/manual/manual.html').  Install them if necessary.

Now apply our buildroot patches with quilt.

  $ cd buildroot-2013.02
  $ QUILT_PATCHES=../N900_RescueOS/buildroot-patches quilt push -a

Point buildroot to the RescueOS configuration:

  $ make defconfig BR2_DEFCONFIG=../N900_RescueOS/buildrootconfig

Invoke buildroot to build RescueOS:

  $ make

Buildroot will download and build a whole bunch of packages, starting with the
cross-compiling toolchain.  When it's done, kernel and cramfs images will be
left in 'buildroot-2013.02/output/images'.