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<p>The following instructions to build the Android source tree apply to all
branches, including <code>master</code>. The basic sequence of build commands
is as follows.</p>
<h2 id="obtaining-proprietary-binaries">Obtain proprietary binaries</h2>
<p>AOSP cannot be used from pure source code only and requires additional
hardware-related proprietary libraries to run, such as for hardware
graphics acceleration. See the sections below for download links and <a
href="requirements.html#binaries">Device binaries</a> for additional
resources.</p>
<aside class ="note">Some devices package these proprietary binaries on their
<code>/vendor</code> partition.</aside>
<h3 id="downloading-proprietary-binaries">Download proprietary binaries</h3>
<p>You can download official binaries for the supported devices running tagged
AOSP release branches from <a
href="https://developers.google.com/android/drivers" class="external">Google's
drivers</a>. These binaries add access to additional hardware capabilities
with non-open source code. To instead build the AOSP master branch, use the
<a href="https://developers.google.com/android/blobs-preview" class="external">
Binaries Preview</a>. When building the master branch for a device, use
the binaries for the <a href="/setup/start/build-numbers.html">most recent
numbered release</a> or with the most recent date.</p>
<h3 id="extracting-proprietary-binaries">Extract proprietary binaries</h3>
<p>Each set of binaries comes as a self-extracting script in a compressed
archive. Uncompress each archive, run the included self-extracting script from
the root of the source tree, then confirm you agree to the terms of the enclosed
license agreement. The binaries and their matching makefiles will be installed
in the <code>vendor/</code> hierarchy of the source tree.</p>
<h3 id="cleaning-up">Clean up</h3>
<p>To ensure the newly installed binaries are properly taken into account after
being extracted, delete the existing output of any previous build using:</p>
<pre class="devsite-terminal devsite-click-to-copy">
make clobber
</pre>
<h2 id="initialize">Set up environment</h2>
<p>Initialize the environment with the <code>envsetup.sh</code> script. Note
that replacing <code>source</code> with <code>.</code> (a single dot) saves a
few characters, and the short form is more commonly used in documentation.</p>
<pre class="devsite-terminal devsite-click-to-copy">
source build/envsetup.sh
</pre>
<p>or</p>
<pre class="devsite-terminal devsite-click-to-copy">
. build/envsetup.sh
</pre>
<h2 id="choose-a-target">Choose a target</h2>
<p>Choose which target to build with <code>lunch</code>. 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:</p>
<pre class="devsite-terminal devsite-click-to-copy">
lunch aosp_arm-eng
</pre>
<p>If run with no arguments <code>lunch</code> will prompt you to choose a
target from the menu.</p>
<p>All build targets take the form <code>BUILD-BUILDTYPE</code>, where the
<code>BUILD</code> is a codename referring to the particular feature
combination. The <code>BUILDTYPE</code> is one of the following:</p>
<table>
<thead>
<tr>
<th>Buildtype</th>
<th>Use</th>
</tr>
</thead>
<tbody>
<tr>
<td>user</td>
<td>limited access; suited for production</td>
</tr>
<tr>
<td>userdebug</td>
<td>like user but with root access and debuggability; preferred for
debugging</td>
</tr>
<tr>
<td>eng</td>
<td>development configuration with additional debugging tools</td>
</tr>
</tbody>
</table>
<p>For more information about building for and running on actual hardware, see
<a href="running.html">Running Builds</a>.</p>
<h2 id="build-the-code">Build the code</h2>
<p>This section is merely a summary to ensure setup is complete. See
<a href="running.html">Running Builds</a> for detailed instructions on building
Android.</p>
<p>Build everything with <code>make</code>. GNU <code>make</code> can handle parallel
tasks with a <code>-jN</code> 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. For example, on a
dual-E5520 machine (2 CPUs, 4 cores per CPU, 2 threads per core),
the fastest builds are made with commands between <code>make -j16</code> and
<code>make -j32</code>.</p>
<pre class="devsite-terminal devsite-click-to-copy">
make -j4
</pre>
<h2 id="run-it">Run it!</h2>
<p>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 <code>lunch</code>,
and it is unlikely to run on a different target than it was built
for.</p>
<aside class="note"><strong>Note:</strong> Remember to <a
href="#obtaining-proprietary-binaries">obtain proprietary binaries</a> or your
build will not boot successfully on your target hardware. If you obtain binary
blobs at this point you will need to unpack them, <code>make clobber</code> and
rebuild.</aside>
<h3 id="flash-a-device">Flash with fastboot</h3>
<p>To flash a device, you will need to use <code>fastboot</code>, which should
be included in your path after a successful build. See <a
href="running.html#flashing-a-device">Flashing a device</a> for
instructions.</p>
<h3 id="emulate-an-android-device">Emulate an Android device</h3>
<p>The emulator is added to your path automatically by the build process. To
run the emulator, type:</p>
<pre class="devsite-terminal devsite-click-to-copy">
emulator
</pre>
<h2 id="troubleshooting-common-build-errors">Troubleshooting common build
errors</h2>
<h3 id="wrong-java-version">Wrong Java version</h3>
<p>If you are attempting to build a version of Android inconsistent with your
version of Java, <code>make</code> will abort with a message such as</p>
<pre>
************************************************************
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
************************************************************
</pre>
<p>Here are the likely causes and solutions:</p>
<ul>
<li>Failing to install the correct JDK as specified in <a
href="requirements.html#jdk">JDK Requirements</a>. Make sure you have followed
the steps in <a href="building.html#initialize">Set up environment</a> and
<a href="building.html#choose-a-target">Choose a target</a>.</li>
<li>Another JDK previously installed appearing in your path. Prepend the
correct JDK to the beginning of your PATH or remove the problematic JDK.</li>
</ul>
<h3 id="python-version-3">Python version 3</h3>
<p>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:</p>
<pre class="devsite-terminal devsite-click-to-copy">
apt-get install python
</pre>
<h3 id="case-insensitive-filesystem">Case insensitive filesystem</h3>
<p>If you are building on an HFS filesystem on Mac OS, you may encounter an
error such as</p>
<pre>
************************************************************
You are building on a case-insensitive filesystem.
Please move your source tree to a case-sensitive filesystem.
************************************************************
</pre>
<p>Please follow the instructions in <a href="initializing.html#creating-a-case-sensitive-disk-image">Creating a case-sensitive disk image</a>.</p>
<h3 id="no-usb-permission">No USB permission</h3>
<p>On most Linux systems, unprivileged users cannot access USB ports by
default. If you see a permission denied error, follow the instructions in
<a href="initializing.html#configuring-usb-access">Configuring USB access</a>.</p>
<p>If adb was already running and cannot connect to the device after
getting those rules set up, it can be killed with <code>adb kill-server</code>.
That will cause adb to restart with the new configuration.</p>
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