Last change: 2000-07-22,  Written by Clifford Wolf.


** Mini-Howto for building a rescue system for the PowerPC platform

When reading this document (and performing the steps described here) you should
have allready some experience with making native builds of ROCK Linux.

First you need to download the ROCK Linux sources and the package sources, as
described in the documentation for the native builds. You don't need an NFS
server becouse we only can do a stage-1-build (the NFS server is only needed
for the stages 2-5). Let's say you installed all this stuff in /rock-linux.


** Step 1: Configuring ROCK Linux

You need to tell ROCK Linux what you want to do (a cross build for the
powerpc architecture):

 murphy:/rock-linux# echo arch=powerpc        >   Config
 murphy:/rock-linux# echo buildoptpkgs=0      >>  Config
 murphy:/rock-linux# echo buildextpkgs=0      >>  Config
 murphy:/rock-linux# echo crossnative=cross   >>  Config

Optionally you can also turn off the 'abort-on-error' feature - so the
build system will continue building the other packages if one package
failed to build. For sure - that doesn't work well if a package like glibc
fails to build.

 murphy:/rock-linux# echo abortonerror=0      >>  Config


** Step 2: Creating a cross compiler

If you have allready installed a cross compiler for PowerPCs, you need to
remove it (only do this if you don't need it anymore or can re-install
it later):

 murphy:/rock-linux# rm -rf /usr/powerpc-unknown-linux-gnu
 murphy:/rock-linux# rm -rf /usr/bin/powerpc-unknown-linux-gnu-*
 murphy:/rock-linux# rm -rf /usr/lib/gcc-lib/powerpc-unknown-linux-gnu
 murphy:/rock-linux# rm -rf /usr/local/powerpc-unknown-linux-gnu
 murphy:/rock-linux# rm -rf /usr/local/bin/powerpc-unknown-linux-gnu-*
 murphy:/rock-linux# rm -rf /usr/local/lib/gcc-lib/powerpc-unknown-linux-gnu

Now you need to build the cross compiler. That's really easy with ROCK Linux:

 murphy:/rock-linux# ./scripts/Create-CrossCC

This creates a slightly modified cross compiler which contains some references
to you ROCK Linux build tree (in that example /rock-linux). So you need to
rebuild it when you change the base directory of the build system.


** Step 3: Building the system

Now build the system (that will take a while):

 murphy:/rock-linux# ./scripts/Build-All COPY

The 'COPY' parameter will be ignored since we only build a stage 1 system.
After that you will find all packages in  rock-powerpc-<version>/* .


** Step 4: Installing it

If you have allready an other Linux distribution which runns on the PowerPC
architecture you can perform the following steps allready on your target
machine. But If you need to cross-build ROCK Linux you pretty sure don't
have a Linux running on your PowerPC. So we install it in an NFS-shared
directory on the build host (we simply call that directory /powerpc-root):

 murphy:/rock-linux# for x in rock-powerpc-*/base-pkgs/*.tar.bz2
 > do tar xvIf $x -C /powerpc-root ; done

Now you need to change the lines for 'root' and 'toor' in the new systems
/etc/passwd and /etc/shadow files like that:

/etc/passwd:
 root:x:0:0:root:/root:/bin/sh
 toor:x:0:0:emergency root:/root:/bin/kiss

/etc/shadow:
 root::::::::
 toor::::::::

And we need to create a /bin/sh file becouse there is no bash yet:

 murphy:/rock-linux# ln -svf sh_pdksh /powerpc-root/bin/sh

That's it. Export the /powerpc-root directory using NFS and boot your (NFS-root
enabled) kernel on the target machine. Now you can create a filesystem on your
PowerPC host, copy the cross built system on it, boot from the local disks and
make a native rebuild.


** Appendix 1: Cross-Building a Kernel

Cross-building a linux kernel is pretty easy. We have built allready the
cross compiler. All you need to do now is to extract you kernel sources
somewhere and change the 'ARCH := $(shell uname ...' line in the Makefile
to 'ARCH := ppc'. Now run 'make menuconfig' and 'make vmlinux' as usual.

Don't forget to enable the devfs and nfs-root drivers.


** Appendix 2: Booting the Linux Kernel on PowerPC

[ FIXME: Someone want to write this? ]


** Appendix 3: Booting the Linux Kernel with NFS root

Please read  /usr/src/linux/Documentation/nfsroot.txt  for details.