Re: [gentoo-embedded] newbie - building bootable image for ARM target on I686 host

[Karl Hiramoto]

Brenden Walker wrote:
> I'm new to embedded linux, but been using Gentoo for a long time.. I'd like to use gentoo embedded of course.
>
> I'm working on a project that will likely be deployed on an ARM processor, the application will most likely be written in java so I need to be able to create a bootable ARM *nix image with a JVM installed on it.  Our application would likely reside on writable media, the OS probably RO.
>
> I've setup a Gentoo system for cross dev to arm-unknown-linux-gnu and that all works.  I've setup a seperate root and can emerge packages there.
>
> What I'm stumped on it how to make a bootable disk image.  At this time the plan was to use QEMU to demonstrate the basic process and for use in developing our application, so a disk image suitable for QEMU is what I'm hoping for.
>
The concept of bootable disk doesn't really exist.  On most ARM HW i've 
worked with the way the boot process works is you have a boot loader 
(redboot, uboot, etc) that loads the kernel, then the kernel paramaters 
tell it how to mount the root FS.

QEMU works kinda the same.  QEMU is the boot loader and you tell it the 
kernel image name, then pass the kernel args to mount the root for example:

qemu-system-arm -M versatilepb -hda sda.img -kernel zImage -append 
"root=/dev/sda1 clock=pit"


If your interested in the kernel details theres a general doc in 
<linux>/Documentation/arm/Booting


I have an old (kernel 2.6.19) qemu image, based on one somebody on this 
list posted a long time ago,  that you can boot:
http://karl.hiramoto.org/embedded/qemu-arm.tar.lzma



--karl