嵌入式系统构建工具 - BuildRoot

Buildroot is a set of Makefiles and patches that makes it easy to generate a complete embedded Linux system. Buildroot can generate any or all of a cross-compilation toolchain, a root filesystem, a kernel image and a bootloader image. Buildroot is useful mainly for people working with small or embedded systems, using various CPU architectures (x86, ARM, MIPS, PowerPC, etc.) : it automates the building process of your embedded system and eases the cross-compilation process.

The major Buildroot features are:

• Can handle everything in your embedded system development project: cross-compiling toolchain, root filesystem generation, kernel image compilation and bootloader compilation. Buildroot is also sufficiently flexible that it can also be used for only one or several of these steps.
• Is very easy to set up, thanks to its menuconfig, gconfig and xconfig configuration interfaces, familiar to all embedded Linux developers. Building a basic embedded Linux system with Buildroot typically takes 15-30 minutes.
• Supports several hundreds of packages for userspace applications and libraries: X.org stack, Gtk2, Qt, DirectFB, SDL, GStreamer and a large number of network-related and system-related utilities and libraries are supported.
• Supports multiple filesystem types for the root filesystem image: JFFS2, UBIFS, tarballs, romfs, cramfs, squashfs and more.
• Can generate an uClibc cross-compilation toolchain, or re-use your existing glibc, eglibc or uClibc cross-compilation toolchain
• Has a simple structure that makes it easy to understand and extend. It relies only on the well-known Makefile language.

1. ubuntu 系统下准备编译环境，安装编译所需软件包

$ sudo apt-get install build-essential libncurses5-dev bison flex texinfo zlib1g-dev gettext libssl-dev autoconf

buildroot 用 wget 下载软件包源码，因此需要安装 wget 

$ sudo apt-get install wget

Ubuntu 默认的 shell 是 dash，它跟 buildroot 的脚本有些不兼容。用下面的命令切换到 bash 

$ sudo dpkg-reconfigure dash

2. 下载 buildroot-2012.02，放在 HOME 目录

$ cd $ wget http://buildroot.net/downloads/buildroot-2012.02.tar.bz2 
$ tar jxf buildroot-2012.02.tar.bz2

3. 配置 buildroot

buildroot 采用了和 Linux 内核一样的配置工具，使用非常方便。

$ make menuconfig

to save the build time, please use the external toolchain

Toolchain -> Toolchain type (External toolchain) -> Toolchain (Sourcery CodeBench ARM 2011.03)

4. 编译 buildroot。这可能会花几个小时 这可能会花几个小时，取决于你的 Internet 带宽以及 CPU 性能 

$ make

编译好的软件包会放在 output/target 目录下，这个目录拥有根文件系统的目录结构。

5.最后生成的根文件系统在 /output/image 目录下

如果想要制作在目标平台运行的本机编译(Native Compile)工具链，则在 make menuconfig 时打开下面两个选项： 

1. Build options 子菜单下的 development files in target filesystem

2. Package Selection for the target 子菜单下的 native toolchain in the target filesystem

当然，为了能在目标平台上进行本机编译 还需要在配置时选择一些必要的编译工具以及程序库，如：make, autoconf, automake, bison, m4, flex, libz, libiconv 等等。

注：所谓本机编译(Native Compile) (Native Compile)，是相对于交叉编译而言的。其实这是最常见的编译方式 其实这是最常见的编译方式，即在本机编译 程序用于在本机或与本机兼容的硬件平台上运行 于在本机或与本机兼容的硬件平台上运行。
补充： 

1. autoconf, automake 等软件包依赖于 microperl 软件包。在编译 microperl 时可能会遇到找不到 m4 的错误，这时只须执行 make host-m4 即可产生 buildroot_dir/output/host/usr/bin/m4， m4 ，然后再执行 make， 中断的编译将继续进行。 

2. 编译某些软件包需要 pkg-config for host config host（在编译平台上运行而非在目标平台上运行）

$ make host-pkgconfig

可编译产生 buil buildroot_dir/output/host/usr/bin/pkg-config