Buildroot is a set of makefiles and configurations intended to download and build a series of packages and install them into a target directory.
The central package in a buildroot system is uClibc, a lightweight libc designed for use in an embedded environment.
The buildroot buildroot system has a series of subdirectories containing package makefiles, patches, configuration modules, and working directories.
The configuration system is very much like the old Config.in style linux kernel configuration. The top level Config.in is expected to include those from the subdirectories.
Packages to be installed into the root are in package/. Tools needed to build packages as well as the uClibc library and linker are in toolchain. Finally, target/ contains packages that produce tools for building a filesystem image (currently, cramfs, jffs, or ext2fs).
Each package lives in a subdirectory with the same name as the package. That directory contains a packagename.mk makefile which specifies package name, download URL, version, and a set of (mostly boilerplate) rules download the source, unpack it, configure it, build the package and install it into the root.
Should the upstream source require patching, the diffs should be in the individual package directory the package.mk file should take care of applying them before building the package.
Toplevel/dl is where downloaded source tarballs should be placed by the makefile.
In addition, should a special configuration file be required (many Free source distributions for embedded use utilize kernel style .config files and make oldconfig to use an existing configuration), it too should be in the package directory and the package.mk should copy it into place appropriately during the build process.
The package directory should also contain a Config.in specifying the config variable, name, and help. package/Config.in must be modified to source your Config.in in order for it to actually be seen, as in:
A Makefile.in should add the build target to targets if the config variable has been set, as in
ifeq ($(strip $(BR2_PACKAGE_LIBAPSECURE)),y) TARGETS+=libapsecure endif
Once a tarball is created, partition the CF on the host (development) machine and unpack the tarball onto the CF filesystem.
Now comes the tricky part. When GRUB boots on the target, the CF will be hd0 and the first partition HD0,0. That will not likely be the case on the host system. It is important to install GRUB on the target, not the host!
We assume the host sees the CF as /dev/sdc and it's mounted on /mnt/test
grub-install –recheck –root-directory=/mnt/test /dev/sdc
echo “(hd0) /dev/sdc” > /mnt/test/boot/grub/device.map
chroot /mnt/test /bin/bash grub root (hd0,0) setup (hd0) exit