Building the System

In this document

The following instructions to build the Android source tree apply to all branches, including master.

Choosing a Branch

Some of the requirements for your build environment are determined by which version of the source code you plan to compile. See Codenames, Tags, and Build Numbers for a full listing of branches you may choose from. You may also choose to download and build the latest source code (called "master"), in which case you will simply omit the branch specification when you initialize the repository.

Once you have selected a branch, follow the appropriate instructions below to set up your build environment.

The basic sequence of build commands is as follows:

Initialize

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

or

$ . 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 aosp_arm-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
aosp_arm ARM emulator AOSP, fully configured with all languages, apps, input methods
aosp_maguro maguro AOSP, running on Galaxy Nexus GSM/HSPA+ ("maguro")
aosp_panda panda AOSP, 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 between make -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 a version of Android inconsistent with your version of Java, 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
    https://source.android.com/source/download.html
************************************************************

This may be caused by

  • failing to install the correct JDK as specified in Initializing the Build Environment.

  • 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 in Initializing the Build Environment 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 Initializing the Build Environment 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.