Creating your own version of the operating system for a mobile device is not just a tribute to fashion or a desire to stand out, but a deep process of immersion in the architecture Linux. Custom firmware allows you to rid your smartphone of junk pre-installed by the manufacturer, extend the life of outdated models and gain full control over the hardware. However, the path from downloading the source code to a working system on the phone screen is thorny and requires serious technical training.
Many users mistakenly believe that the assembly Android is available only to professional developers from Google. In fact, a community of enthusiasts such as LineageOS or Pixel Experienceproved the opposite. You will need a powerful computer, a stable Internet connection and, most importantly, patience, since the initial compilation may take several hours.
Before you begin (practical actions), you need to clearly understand the risks. Incorrect assembly or flashing an incompatible image can lead to brick (turning the device into a “brick”). Always have working Fastboot and stock firmware on hand for recovery.
⚠️ Attention: The build process requires in-depth knowledge of the Linux file system. Accidental deletion of system libraries in the host environment can lead to inoperability of your main computer.
Preparing the working environment and choosing a distribution
The foundation of any successful build is a correctly configured operating system. Although it is theoretically possible to build Android on macOS or even Windows (via WSL), LTS remains the industry standard. Most scripts and tools are optimized specifically for this environment, which minimizes the number of potential compatibility errors. Ubuntu LTS. Most scripts and tools are optimized specifically for this environment, which minimizes the number of potential compatibility errors.
You will need a computer with at least 16 GB of RAM, although 32 GB is highly recommended for comfortable work with modern versions of Android (13, 14 and higher). The hard drive must be an SSD, since working with millions of small files in the repository repo on a mechanical HDD can increase synchronization time by 5-10 times.
To get started, you need to install a basic set of dependencies. In the terminal, this looks like installing packages for compilation, working with the network and archives. Please note that package versions can critically affect the process.
- 📦 Git —a version control system, without which it is impossible to work with the source code.
- 🐍 Python —a scripting language used in many Android build utilities.
- ☕ OpenJDK —a Java development kit, the version of which must strictly match the Android version.
- 🔧 Build-essential —a set of compilers (gcc, g++) and assembly tools.
Pay special attention to the version JDK. Android 11 requires Java 8, Android 12 requires Java 11, and newer versions often require Java 17. Installing the wrong version will result in early compilation errors that are difficult for a newbie to debug.
Use virtual machines or Docker containers to isolate your build environment. This will allow you to easily rollback to a clean state if experiments with libraries break the system.
Initializing repositories and downloading source code
After preparing the environment, the next step is to obtain the source code. Android Open Source Project (AOSP) is stored in a distributed system managed by the utility repo. This utility is a wrapper around Git and allows you to manage hundreds of individual repositories as a single entity.
First, you need to download the repo script itself and add it to the execution path. Then a working directory is created where the source tree will be expanded. The initialization command requires specifying a manifest - an XML file that describes which repositories and in which branches need to be downloaded.
repo init -u https://android.googlesource.com/platform/manifest -b android-14.0.0_r1The parameter -b indicates a specific branch (branch). An error in choosing a branch will result in you downloading code for a different version of the system or an unstable development version. After initialization, the synchronization process starts, which can last from 30 minutes to several hours depending on the Internet speed.
⚠️ Attention: The volume of downloaded data can exceed 50-70 GB. Make sure that there is enough free space on the disk, otherwise the process will be interrupted in the middle and you will have to start over.
For devices from specific manufacturers (Xiaomi, Samsung, OnePlus), AOSP forks are often used, such as CyanogenMod (now LineageOS) or Dirty Unicorns. In this case, the URL of the repository in the team repo init will differ from the standard Google one.
Device drivers and proprietary blocks (Blobs)
Pure Android code does not contain drivers for specific hardware. Cameras, modems, sound chips and sensors work thanks to closed binary blocks that manufacturers are required to provide. These files are called vendor blobs.
Without these files, the assembled system will either not boot or will work with critical errors (there will be no communication, sound or touchscreen). There are two main ways to obtain these files: extracting from the device's stock firmware or cloning a ready-made repository from GitHub if the community has already taken care of that.
If you extract the files yourself, the device must be rooted and connected via adb. A special script extract-files.sh, usually located in the device tree, will automatically copy the necessary libraries to the folder vendor of your build project.
| Component | File type | Location on the system | Criticality |
|---|---|---|---|
| Radio / Modem | .bin /.so | /vendor/lib/libril.so | High (no network) |
| GPU Driver | .so | /vendor/lib/libGLES_mali.so | High (no graphics) |
| Camera HAL | .so | /vendor/lib/hw/camera.*.so | Medium (black screen in the camera) |
| Audio FX | .so | /vendor/lib/soundfx/* | Low (no sound effects) |
It is important to monitor the compatibility of driver versions with the kernel version and Android. Updating the system without updating proprietary blocks often leads to unstable operation or a cyclic reboot (bootloop).
What to do if the drivers are not suitable?
If you are building a new version of Android on an old device, some proprietary libraries may not work due to changes in the API. In such cases, developers often create transitional compatibility layers (shims) that replace function calls.
Device tree configuration and kernel compilation
A device tree (Device Tree) is a set of configuration files that tell the build system exactly how to work with a particular smartphone. It describes memory sections, kernel parameters, key layout and hardware platform features.
The kernel (Kernel) is the heart of the system. It can be compiled separately or as part of a general assembly. For modern devices, GKI (Generic Kernel Image) is often used, which simplifies the process, but for older models, building a custom kernel with specific patches from the manufacturer is required.
The process of setting up the device tree requires editing the files BoardConfig.mk and device.mk. They specify paths to drivers, enable functions (for example, support for VoLTE or Fast Charge) and set partition parameters.
- 📝 fstab — a table of file systems that determines how partitions are mounted at boot.
- ⚙️ init.rc —initialization scripts that start services and configure access rights.
- 📡 overlays —resources, allowing you to change system settings without changing the main code (brightness, element sizes).
Errors in the kernel configuration are the most common cause of failures. An incorrectly specified memory address or an incorrect kernel command line parameter may cause the bootloader logo to appear, but the system will not go further.
⚠️ Attention: Kernel configuration interfaces and compilation options may vary depending on the Android version and chipset manufacturer (Qualcomm, MediaTek, Exynos). Always check the documentation for your specific platform.
Running the build process and optimizing parameters
When all components are ready, the longest stage begins - compilation. The build command (lunch) selects the target configuration (for example, aosp_bacon-userdebug), after which the script is executed mka or make.
To speed up the process, you can use multi-threaded compilation by specifying the number of available processor cores. However, setting the value too high can lead to a lack of RAM and an abnormal termination of the process.
export USE_CCACHE=1export CCACHE_EXEC=/usr/bin/ccache
ccache -M 50G
mka bacon -j16
The compilation caching system is used here. When rebuilding after making minor code changes, ccache allows you to avoid recompiling unchanged files, reducing the time from hours to minutes. ccache — compilation caching system. When rebuilding after making minor code changes, ccache avoids recompiling unchanged files, reducing the time from hours to minutes.
You will see many warnings during the build process. Most of them can be ignored, but Errors will stop the process. Analyzing the logs at this point is critical to understanding which file or library is missing.
Using ccache and correctly setting the number of threads (-j) can reduce build time by 3-4 times, saving hours of your time with each development iteration.
Debugging errors and testing the finished image
After successful compilation, an image file will appear in the folder out/target/product/ (usually .zip for flashing via recovery or .img for fast loading). But the appearance of the file does not guarantee that the system will work stably.
It is better to carry out the first testing in an emulator or on a secondary device. Connect your smartphone in fastboot mode and try to flash the image. If the device goes into a cyclic reboot, you need to connect through adb logcat immediately after turning on to catch the moment the system crashes.
Common problems include lack of superuser rights (if they are not built-in), Wi-Fi not working due to incorrect drivers, or "green screen" in applications due to problems with video encoding hardware acceleration.
☑️ Final check before release
Only after eliminating all critical bugs can the assembly be considered ready for everyday use. The debugging process may take longer than the initial compilation itself, but it is what turns a set of code into a full-fledged product.
How long does the first build of Android take?
The time depends on the power of your PC. On a mid-range processor (such as Ryzen 5 or Core i5) with 16 GB of RAM, the first full build can take 4 to 8 hours. Repeated builds using ccache take from 15 minutes to 1 hour.
Is it possible to build Android on Windows?
Native assembly on Windows is extremely difficult and is not recommended. The best solution is to use the WSL2 subsystem (Windows Subsystem for Linux) with Ubuntu installed inside, or launch a full-fledged virtual machine.
What is a "vendor" section and why do you need it?
The vendor section contains proprietary drivers and libraries specific to a particular device. Without this section, the operating system will not be able to interact with the unique hardware of the smartphone (camera, modem, sensors).
Do you need to unlock the bootloader to install your build?
Yes, installing custom firmware requires an unlocked bootloader. With a locked bootloader, the phone will only accept system images signed by the manufacturer.