Establishing a Build Environment

This section describes how to set up your local work environment to build the Android source files. You must use Linux or macOS; building under Windows is not currently supported.

For an overview of the entire code-review and code-update process, see Life of a Patch.

Choosing a branch

Some requirements for the build environment are determined by the version of the source code that you plan to compile. For a full list of available branches, see Build Numbers. You can also choose to download and build the latest source code (called master), in which case you simply omit the branch specification when you initialize the repository.

After selecting a branch, follow the appropriate instructions below to set up your build environment.

Setting up a Linux build environment

These instructions apply to all branches, including master.

The Android build is routinely tested in house on recent versions of Ubuntu LTS (14.04) and Debian testing. Most other distributions should have the required build tools available.

For Gingerbread (2.3.x) and higher versions, including the master branch, a 64-bit environment is required. Older versions can be compiled on 32-bit systems.

Installing required packages (Ubuntu 14.04)

You need a 64-bit version of Ubuntu (14.04 is recommended).

sudo apt-get install git-core gnupg flex bison gperf build-essential zip curl zlib1g-dev gcc-multilib g++-multilib libc6-dev-i386 lib32ncurses5-dev x11proto-core-dev libx11-dev lib32z-dev libgl1-mesa-dev libxml2-utils xsltproc unzip

Note: To use SELinux tools for policy analysis, also install the python-networkx package.

Note: If you're using LDAP and want to run ART host tests, also install the libnss-sss:i386 package.

Installing required packages (Ubuntu 12.04)

You may use Ubuntu 12.04 to build older versions of Android. Version 12.04 isn't supported on master or recent releases.

sudo apt-get install git 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 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

Installing required packages (Ubuntu 10.04-11.10)

Building on Ubuntu 10.04-11.10 is no longer supported, but may be useful for building older releases of AOSP.

sudo apt-get install git gnupg flex bison gperf build-essential zip curl zlib1g-dev libc6-dev lib32ncurses5-dev ia32-libs x11proto-core-dev libx11-dev lib32readline5-dev lib32z-dev libgl1-mesa-dev g++-multilib mingw32 tofrodos python-markdown libxml2-utils xsltproc

On Ubuntu 10.10:

sudo ln -s /usr/lib32/mesa/libGL.so.1 /usr/lib32/mesa/libGL.so

On Ubuntu 11.10:

sudo apt-get install libx11-dev:i386

Configuring USB access

Install a community-maintained default set of udev rules for all Android devices by following the instructions to Set up a device for development.

Using a separate output directory

By default, the output of each build is stored in the out/ subdirectory of the matching source tree.

On some machines with multiple storage devices, builds are faster when storing the source files and the output on separate volumes. For additional performance, the output can be stored on a file system optimized for speed instead of crash robustness, because all files can be regenerated if the file system is corrupted.

To set this up, export the OUT_DIR_COMMON_BASE variable to point to the location where your output directories will be stored.

export OUT_DIR_COMMON_BASE=<path-to-your-out-directory>

The output directory for each separate source tree is named after the directory holding the source tree. For instance, if you have source trees /source/master1 and /source/master2 and if OUT_DIR_COMMON_BASE is set to /output, the output directories are /output/master1 and /output/master2.

Avoid having multiple source trees stored in directories that have the same name, as the source trees would end up sharing an output directory, with unpredictable results. This is only supported on Jelly Bean (4.1) and higher, including the master branch.

Setting up a macOS build environment

In a default installation, macOS runs on a case-preserving but case-insensitive file system. This type of file system isn't supported by Git and causes some Git commands (such as git status) to behave abnormally. Because of this, we recommend that you always work with the AOSP source files on a case-sensitive file system. This can be done fairly easily using a disk image, discussed below.

When the proper file system is available, building the master branch in a modern macOS environment is straightforward. Earlier branches require some additional tools and SDKs.

Creating a case-sensitive disk image

You can create a case-sensitive file system within your existing macOS environment using a disk image. To create the image, launch Disk Utility and select New Image. A size of 25 GB is the minimum to complete the build; more space is best for future growth. Using sparse images saves space while allowing growth as needed. Select case sensitive, journaled as the volume format.

You can also create the file system from a shell with the following command:

hdiutil create -type SPARSE -fs 'Case-sensitive Journaled HFS+' -size 40g ~/android.dmg

This creates a .dmg (or possibly a .dmg.sparseimage) file which, when mounted, acts as a drive with the required formatting for Android development.

If you need a larger volume later, you can resize the sparse image with the following command:

hdiutil resize -size <new-size-you-want>g ~/android.dmg.sparseimage

For a disk image named android.dmg stored in your home directory, you can add helper functions to ~/.bash_profile:

To mount the image when you execute mountAndroid:
```
# mount the android file image
mountAndroid() { hdiutil attach ~/android.dmg -mountpoint /Volumes/android; }
```
Note: If your system created a .dmg.sparseimage file, replace ~/android.dmg with ~/android.dmg.sparseimage.

To unmount it when you execute umountAndroid:

# unmount the android file image
umountAndroid() { hdiutil detach /Volumes/android; }

After you've mounted the android volume, you do all your work there. You can eject it (unmount it) just as you would an external drive.

Installing Xcode and other packages

Install the Xcode command line tools:
```
xcode-select --install
```
For older versions of macOS (10.8 or lower), you must install Xcode from the Apple developer site. If you aren't registered as an Apple developer, you must create an Apple ID to download.
Install either MacPorts or Homebrew for package management.
Ensure that the associated directory is in your path within your ~/.bash_profile file:
1. MacPorts - /opt/local/bin must appear before /usr/bin:
```
export PATH=/opt/local/bin:$PATH
```
2. Homebrew - /usr/local/bin:
```
export PATH=/usr/local/bin:$PATH
```
3. For MacPorts, issue:
```
POSIXLY_CORRECT=1 sudo port install git gnupg
```
4. For Homebrew, issue:
```
brew install git gnupg2
```
Setting a file descriptor limit

On macOS, the default limit on the number of simultaneous open file descriptors is too low and a highly parallel build process may exceed this limit. To increase the cap, add the following lines to your ~/.bash_profile:
```
# set the number of open files to be 1024
ulimit -S -n 1024
```
Next: Download the source

Your build environment is good to go! Proceed to downloading the source.