Building the android System from source

2013年02月04日 综合技术 评论 13 条 阅读 3,833 次

Building the System

The basic sequence of build commands is as follows:


Initialize the environment with the envsetup.sh script. Note that replacing "source" with a single dot saves a few characters, and the short form is more commonly used in documentation.

$ source build/envsetup.sh


$ . build/envsetup.sh

Choose a Target

Choose which target to build with lunch. The exact configuration can be passed as an argument, e.g.

$ lunch full-eng

The example above refers to a complete build for the emulator, with all debugging enabled.

If run with no arguments lunch will prompt you to choose a target from the menu.

All build targets take the form BUILD-BUILDTYPE, where the BUILD is a codename referring to the particular feature combination. Here's a partial list:

Build name Device Notes
full emulator fully configured with all languages, apps, input methods
full_maguro maguro full build running on Galaxy Nexus GSM/HSPA+ ("maguro")
full_panda panda full build running on PandaBoard ("panda")

and the BUILDTYPE is one of the following:

Buildtype Use
user limited access; suited for production
userdebug like "user" but with root access and debuggability; preferred for debugging
eng development configuration with additional debugging tools

For more information about building for and running on actual hardware, see Building for devices

Build the Code

Build everything with make. GNU make can handle parallel tasks with a -jN argument, and it's common to use a number of tasks N that's between 1 and 2 times the number of hardware threads on the computer being used for the build. E.g. on a dual-E5520 machine (2 CPUs, 4 cores per CPU, 2 threads per core), the fastest builds are made with commands betweenmake -j16 and make -j32.

$ make -j4

Run It!

You can either run your build on an emulator or flash it on a device. Please note that you have already selected your build target with lunch, and it is unlikely at best to run on a different target than it was built for.

Flash a Device

To flash a device, you will need to use fastboot, which should be included in your path after a successful build. Place the device in fastboot mode either manually by holding the appropriate key combination at boot, or from the shell with

$ adb reboot bootloader

Once the device is in fastboot mode, run

$ fastboot flashall -w

The -w option wipes the /data partition on the device; this is useful for your first time flashing a particular device, but is otherwise unnecessary.

For more information about building for and running on actual hardware, see Building for devices

Emulate an Android Device

The emulator is added to your path automatically by the build process. To run the emulator, type

$ emulator

Using ccache

ccache is a compiler cache for C and C++ that can help make builds faster. In the root of the source tree, do the following:

$ export USE_CCACHE=1
$ export CCACHE_DIR=/<path_of_your_choice>/.ccache
$ prebuilts/misc/linux-x86/ccache/ccache -M 50G

The suggested cache size is 50-100G.

You can watch ccache being used by doing the following:

$ watch -n1 -d prebuilts/misc/linux-x86/ccache/ccache -s

On OSX, you should replace linux-x86 with darwin-x86.

When using Ice Cream Sandwich (4.0.x) or older, you should replace prebuilts/misc with prebuilt.

Troubleshooting Common Build Errors

Wrong Java Version

If you are attempting to build froyo or earlier with Java 1.6, or gingerbread or later with Java 1.5, make will abort with a message such as

You are attempting to build with the incorrect version
of java.

Your version is: WRONG_VERSION.
The correct version is: RIGHT_VERSION.

Please follow the machine setup instructions at

This may be caused by

  • failing to install the correct JDK as specified on the Initializing page. Building Android requires Sun JDK 5 or 6 depending on which release you are building.
  • another JDK that you previously installed appearing in your path. You can remove the offending JDK from your path with:
    $ export PATH=${PATH//path/to/jdk/dir:/}

Python Version 3

Repo is built on particular functionality from Python 2.x and is unfortunately incompatible with Python 3. In order to use repo, please install Python 2.x:

$ apt-get install python

Case Insensitive Filesystem

If you are building on an HFS filesystem on Mac OS X, you may encounter an error such as

You are building on a case-insensitive filesystem.
Please move your source tree to a case-sensitive filesystem.

Please follow the instructions on the Initializing page for creating a case-sensitive disk image.

No USB Permission

On most Linux systems, unprivileged users cannot access USB ports by default. If you see a permission denied error, follow the instructions on the Initializing page for configuring USB access.

If adb was already running and cannot connect to the device after getting those rules set up, it can be killed with adb kill-server. That will cause adb to restart with the new configuration.