Follow these instructions to begin building Android.
Setting up the environment
Initialize the environment with the
You need to reissue this command after every
repo sync to pick up
any changes to that script. Note that replacing
. (a single
dot) saves a few characters, and the short form is more commonly used in documentation.
envsetup.sh script imports several commands that enable
you to work with the Android source code, including the commands used in this
To see the full list of available commands, run:
Choosing a target
Choose which target to build with
product_name as the product to build, and build_variant
as the variant to build, and stores those selections in the environment to be
read by subsequent invocations of
m and other similar commands.
The exact configuration can be passed as an argument. For example, the following command refers to a complete build for the emulator, with all debugging enabled:
If run with no arguments,
lunch prompts you to choose a
target from the menu, but note that the menu doesn't include every possibility.
a device build for the build configurations of all devices supported in AOSP,
or talk to people on your team about the correct lunch for the device you're
All build targets take the form
BUILD is a codename referring to the particular feature
BUILDTYPE is one of the following.
|user||Limited access; suited for production|
|userdebug||Like user but with root access and debug capability; preferred for debugging|
|eng||Development configuration with additional debugging tools|
The userdebug build should behave the same as the user build, with the ability to enable additional debugging that normally violates the security model of the platform. This makes the userdebug build good for user testing with greater diagnosis capabilities. When developing with the userdebug build, follow the userdebug guidelines.
The eng build prioritizes engineering productivity for engineers who work on the platform. The eng build turns off various optimizations used to provide a good user experience. Otherwise, the eng build has behavior similar to the user and userdebug builds so that device developers can see how the code behaves in those environments.
For more information about building for and running on actual hardware, see Flashing Devices.
tapas command configures the build of unbundled apps. It selects individual apps
to be built by the Android build system. Unlike
tapas does not
request the building of images for a device.
tapas help for more information on the command.
Building the code
This section is a quick summary to ensure that setup is complete.
Build everything with
m can handle parallel
tasks with a
-jN argument. If you don't provide a
argument, the build system automatically selects a parallel task count that it
thinks is optimal for your system.
As explained above, you can build specific modules instead of the full
device image by listing their names in your
m command line. In
m provides some pseudotargets for special purposes. Some
m droidis the normal build. This target is here because the default target requires a name.
m allbuilds everything that
m droiddoes, plus everything that doesn't have the
droidtag. The build server runs this to make sure that everything that is in the tree and has an
m- Runs builds from the top of the tree. This is useful because you can run
makefrom within subdirectories. If you have the
TOPenvironment variable set, it uses that. If you don't, it looks up the tree from the current directory, trying to find the top of the tree. You can either build the whole source code tree by running
mwithout arguments or build specific targets by specifying their names.
mma- Builds all of the modules in the current directory, and their dependencies.
mmma- Builds all of the modules in the supplied directories, and their dependencies.
cdto the top of the tree.
m cleandeletes all of the output and intermediate files for this configuration. This is the same as
rm -rf out/.
m help to see what other pseudotargets
Running the build
You can either run your build on an emulator or flash it on a device.
Because you've already selected your build target with
it's unlikely to run on a different target than it was built for.
Flashing with fastboot
To flash a device, use
fastboot, which should
be included in your path after a successful build. See Flashing a device for
Emulating an Android device
The emulator is added to your path automatically by the build process. To run the emulator, type:
Understanding build fingerprints
To track and report issues tied to a particular Android build, it is important to understand the build fingerprint. The build fingerprint is a unique, human-readable string containing manufacturer information issued to each build. See the FINGERPRINT description within the Build Parameters section of the Android Compatibility Definition Document (CDD) for the precise syntax.
The build fingerprint represents a particular Android implementation and revision. This unique key allows app developers and others to report issues with specific firmware versions. See Reporting bugs for the Android issue-reporting process.
A build fingerprint encapsulates all Android implementation details:
- APIs: Android and native, as well as soft API behaviors
- Core API and some system UI behavior
- Compatibiility and security requirements defined in the CDD
- Product specifications and the uses-feature setting employed by apps to target devices meeting expected requirements
- Implementations of hardware and software components
Troubleshooting common build errors
Wrong Java version
If you're attempting to build a version of Android that's inconsistent with
your version of Java,
make aborts 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/initializing.html ************************************************************
Here are the likely causes and solutions:
- Failure to install the correct JDK as specified in the JDK requirements. Make sure you've followed the steps in Setting up the environment and Choosing a target.
- Another JDK previously installed appearing in your path. Prepend the correct JDK to the beginning of your path or remove the problematic JDK.
No USB permission
By default on most Linux systems, unprivileged users can't access USB ports. If you see a permission denied error, follow the instructions in Configuring USB access.
If ADB was already running and can't connect to the device
after getting those rules set up, you can kill it with
That command causes ADB to restart with the new configuration.