参考：http://source.android.com/source/initializing.html
Installing required packages (Ubuntu 12.04)
Building on Ubuntu 12.04 is currently only experimentally supported and is not guaranteed to work on branches other than master.
$ sudo apt-get install git-core gnupg flex bison gperf build-essential \ zip curl libc6-dev libncurses5-dev:i386 x11proto-core-dev \ libx11-dev:i386 libreadline6-dev:i386 libgl1-mesa-glx:i386 \ libgl1-mesa-dev g++-multilib mingw32 openjdk-6-jdk tofrodos \ python-markdown libxml2-utils xsltproc zlib1g-dev:i386 $ sudo ln -s /usr/lib/i386-linux-gnu/mesa/libGL.so.1 /usr/lib/i386-linux-gnu/libGL.so
准备完毕后，开始真正的下载工作了
Downloading the Source Tree
Installing Repo
Repo is a tool that makes it easier to work with Git in the context of Android. For more information about Repo, see Version Control .
To install, initialize, and configure Repo, follow these steps:
$ mkdir ~/bin
$ PATH=~/bin:$PATH
Download the Repo script and ensure it is executable:
$ curl https://dl-ssl.google.com/dl/googlesource/git-repo/repo > ~/bin/repo
$ chmod a+x ~/bin/repo
然而，实际下载确因总总原因无法下载
网上有好心人准备地址：
curl "http://php.webtutor.pl/en/wp-content/uploads/2011/09/repo" > ~/bin/repo
然后下面步骤，就是准备你下载的目录
$ mkdir WORKING_DIRECTORY
$ cd WORKING_DIRECTORY
Run repo init to bring down the latest version of Repo with all its most recent bug fixes. You must specify a URL for the manifest, which specifies where the various repositories included in the Android source will be placed within your working directory.
$ repo init -u https://android.googlesource.com/platform/manifest
To check out a branch other than "master", specify it with -b:
$ repo init -u https://android.googlesource.com/platform/manifest -b android-4.0.1_r1
然后执行：却出错
fatal: '../platform/abi/cpp.git' does not appear to be a git repository
fatal: The remote end hung up unexpectedly
error: Cannot fetch platform/abi/cpp
解决方法：
在.repo目录下的manifest.xml里找到fetch属性
改成
fetch= "git://Android.git.linaro.org/"
然后就可以下载了...耐心等待把...中间可能会被报错停止掉,重新repo sync 就可以了