CLFS stands for Cross Linux From Scratch, it's an offshoot of the LFS (Linux From Scratch) project. The goal of both LFS and CLFS is to provide instruction on how to build a Linux system, step by step, from source. In both projects, first a toolchain is built and then a bootable GNU/Linux operating system is built using that toolchain. CLFS differs from LFS in that CLFS builds a GNU/Linux system for an architecture different than the one doing the building. For example, if I have an x86 based computer on my desk that I want to use to build GNU/Linux for a PowerPC system I just bought off eBay, I'd use CLFS rather than LFS.
The methods described by CLFS are very similar to the methods used by OpenEmbedded orBuildroot, but each step is described and there's very little automation. You literally manually build, step by step from upstream source, a toolchain and then a functioning GNU/Linux system. Throughout the books there is information on all the different choices you are required to make. For example: if targeting an ARM processor, when building GCC, you have to choose which ARM version to target, like "armv7-a" for Cortex-A8.
The CLFS project has three different books: Standard, Embedded, and Sysroot. The Standard book is the most developed book and mostly targets people who want to build a cross-compiled system for a desktop computer system. The Embedded book (the one I work on) builds a minimal GNU/Linux system using uClibc targeted at embedded devices where resources may be constrained. The Sysroot book uses a different technique to accomplish similar goals as the Standard book. Both the Standard and Embedded books are under active development, Sysroot hasn't been updated in a while.
Where OpenEmbedded and Buildroot hide a lot of the complexity of building a cross compiled version of GNU/Linux, CLFS hides almost nothing. Think of CLFS as more of a learning experience rather than a quick way to build a cross system. A big advantage of CLFS over an automated system is that errors are usually easy to identify, since everything's done manually you stay at the terminal and you'll probably watch the configure scripts and compiler output. If something doesn't look right, you will have a much better idea of where the problem is, if not what the problem is.
- buildroot whose main purpose is to build complete root file systems, hence the name. But once you have your toolchain with buildroot, part of it is installed in the root-to-be, so if you want to build a whole new root, you either have to save the existing one as a template and restore it later, or restart again from scratch. This is not convenient,
- ptxdist, whose purpose is very similar to buildroot,
- other projects (openembedded for example), which is again used to build complete root file systems.
crosstool-NG is really targetted at building toolchains, and only toolchains. It is then up to you to use it the way you want.
With crosstool-NG, you can learn precisely how each component is configured and built, so you can finely tweak the build steps should you need it.
crosstool-NG can build from generic, general purpose toolchains, to very specific and dedicated toolchains. Simply fill in specific values in the adequate options.
sudo apt-get install -y libsdl-dev
yum search sdl
sudo yum install SDL-devel
export LDFLAGS=-lrt; ./configure --target-list=arm-softmmu --prefix=$HOME/local; make
$ qemu-system-arm --version
flashimg -s 64M -t nand -f nand.bin -p uboot.part -w boot,u-boot.bin -w kernel,uImage -w root,rootfs.jffs2 -z 512
qemu-system-arm -M mini2440 -serial stdio -mtdblock nand.bin -usbdevice mouse
使用 QEMU 创建虚拟机
sudo yum install glib2-devel
./configure --enable-kvm --enable-debug --enable-vnc
find . -perm -1 -print