Creating your own operating system for a mobile device is a pinnacle in the world of modding, which opens up limitless customization possibilities for the developer. Many enthusiasts dream of not just installing a ready-made LineageOS or Pixel Experience, but of assembling a unique image optimized for specific hardware or containing exclusive functions. This process is complex, requires deep knowledge of the Linux architecture and the availability of powerful hardware, but the result is worth it.
Before you start compiling, you need to clearly understand what you are going to do: port an existing project to a new device or build a system from scratch based on AOSP (Android Open Source Project). The first option is more realistic for an individual, while the second requires a team of professionals and months of work. In this article, we will look at the key stages of preparing the environment and direct assembly.
You will need a computer with an operating system Linux (preferably Ubuntu or Debian), at least 100 GB of free space on an SSD and at least 16 GB of RAM. If you are ready to dive into the world of the terminal and source code, let's begin this exciting journey.
Preparing the working environment and tools
The foundation of any successful build is a properly configured development environment. Errors at this stage can lead to the compilation being interrupted at 90% of the process, which, if it takes several hours, will be a fatal blow to the nerves. To work with source code Android it is critically important to use the latest version of the distribution, since old libraries may not support new compilation standards.
First of all, you need to install a basic set of utilities, without which the build system simply will not start. This includes compilers, version managers and archive tools. Install the following packages via the terminal:
- 🛠️ Git —a version control system required for loading code repositories.
- 📦 Repo —a tool from Google for managing multiple Git repositories at the same time.
- ⚙️ Build-essential —a set of compilers (gcc, g++) and libraries for compiling apps.
- 🐍 Python and OpenJDK —the runtime environment and Java compiler required to build system applications.
After installing the basic software, you need to configure environment variables. This will allow the system to see executable files and libraries in the required directories. Pay special attention to the version JDK: different versions Android require different versions of Java (for example, Android 11 requires Java 8, and Android 12 and above requires Java 11).
⚠️ Attention: The non-compliance of the Java version with the requirements of a specific Android version will lead to compilation errors in the early stages. Always check the requirements in the official documentation before installing the software.
Setting access rights also plays an important role. Often build scripts require running commands as a superuser or having specific permissions on files. Make sure that your user is added to the group sudo and has rights to execute scripts in the working directory.
Downloading source code and synchronizing repositories
When the tools are ready, the stage of downloading the code itself begins. Sources AOSP take up a colossal amount of space - more than 250 GB in uncompressed form. The download process can take from several hours to a day, depending on the speed of your Internet connection and the selected development branch.
To initialize the working directory, use the command repo init. Here you specify the Google repository URL and the specific branch you want to build. For example, to build the current stable version, you will choose a tag like android-13.0.0_r1. An error in selecting a tag can lead to unstable operation of the system or lack of drivers.
Then follows the command repo sync, which begins downloading all the necessary projects. This process is parallel, but resource-intensive. It is recommended to use optimization flags, such as -j4 or -cto speed up loading and save bandwidth by downloading only the current branch.
Use mirror repositories located geographically closer to you to speed up loading source code by 3-5 times.
It is important to understand the structure of the loaded data. You will receive not one monolithic file, but thousands of separate Git repositories, each of which is responsible for its own module: from the system kernel to the calculator. Manifest the file manages the connections between them.
Working with Device Tree and .vendor images
The most difficult stage for custom developers is adapting the system for a specific device (“device”). Pure AOSP does not contain proprietary drivers and hardware configurations of your smartphone. For this purpose, there are so-called Device Trees (device trees) and Vendor Blobs.
Device trees describe the hardware configuration: button location, screen parameters, camera and communication module settings. Without a correct Device Tree, the system simply will not be able to initialize the hardware. Typically, developers take a tree from a similar device as a basis or use ready-made solutions from forums like XDA Developers.
Proprietary files (blobs) are closed drivers from the manufacturer of the processor (Qualcomm, MediaTek) or components (Sony, Samsung). They cannot be legally distributed as part of open source, so they are often downloaded from the device’s stock firmware and placed in the folder vendor.
| Component | Purpose | Where to get it |
|---|---|---|
| Kernel Source | System kernel, hardware management | GitHub of the manufacturer or device |
| Device Tree | Configuration of a specific smartphone | Custom firmware repositories |
| Vendor Blobs | Closed drivers (WiFi, BT, GPU) | Extracting from stock firmware |
| Bootloader | Loader that verifies signatures | Official website of the vendor |
Integration of these components requires editing many configuration files, such as BoardConfig.mk and device.mk. Any typo in the paths to the files will lead to the fact that the builder will not find the required resource and will interrupt the work.
Kernel compilation and system image assembly
After all the sources are in place and the device configuration is entered, the compilation process begins. This is the most resource-intensive stage, which loads the processor and RAM by 100%. The assembly time depends on the power CPU: on a modern 8-core processor it can take from 40 minutes to 2 hours.
To start the process, a script is used source build/envsetup.sh, which loads the assembly functions into the current terminal session. Then you select the target device with command lunch, specifying the build code (for example, aosp_flo-userdebug).
source build/envsetup.shlunch aosp_flo-userdebug
mka bacon
Command mka (Make Kati) is an optimized version of the standard make and works faster by parallelizing tasks. Parameter bacon indicates for the purpose of the build - creating a ready-made zip archive with the firmware. In the process, you will see a stream of logs, where green lines indicate success, and red lines indicate errors.
⚠️ Attention: If errors like "Error: could not load file" appear in the logs, check the paths in the Device Tree. A common problem is the absence of symbolic links to vendor libraries.
If the build was successful, in the folder out/target/product/your_device and recovery. This set of files is your finished firmware. boot.img, system.img, vendor.img and recovery. This set of files is your finished firmware.
Debugging errors and optimizing size
It is rare that the first build goes perfectly. Most often, the developer is faced with a bootloop (cyclic reboot) or lack of communication. To analyze the reasons for the system crash, you need to use logs - logcat, which displays system logs in real time.
Connect the device via USB and execute the command adb logcat immediately after turning it on. Look for lines with the tag FATAL or AndroidRuntime, which indicate a critical service failure. Often the problem lies in the incompatibility of the version SELinux or the absence of the required one. permissions in the manifest.
Optimizing the size of the firmware is also important, especially for devices with low memory. You can exclude unnecessary applications from the build by editing the file. product.mkRemoving standard games, browsers or Google services can save up to 500 MB of space.
How to speed up the restart. assembly?
Use the directive ccache. It caches the compilation results. When reassembling, if the code has not changed, the compiler will take ready-made objects from the cache, which will speed up the process by 5-10 times.
Another aspect of optimization is the choice of task scheduler and kernel settings Change. parameters in defconfig kernels can improve autonomy or performance, but require careful testing.
Testing and installing custom firmware
When the image is ready and debugged, the moment of truth comes - installation on the device. To do this, your smartphone must have an unlocked bootloader (Bootloader) and a custom recovery installed, for example TWRP. Without these conditions, installation is impossible.
Before the first installation, be sure to make a full backup of your data through recovery. The process of flashing a new build often requires formatting the Data i Cachepartitions, which will lead to the deletion of all user files.
- 📂 Copy the zip archive of the firmware to the internal memory of the device.
- 🔄 Reboot into Recovery mode (usually Volume Up + Power).
- 🧹 Perform Wipe Data/Factory Reset and clearing Cache/Dalvik.
- 📲 Select Install and specify the archive with your firmware.
After installation and the first boot (which can last up to 10 minutes), perform a basic testing: check the operation of the sensor, sound, cameras and communication modules. If everything works stably, congratulations - you have created your own firmware!
Successfully building the firmware is only half the battle. Stability in everyday scenarios determines the quality of your product.
Is it possible to build firmware on Windows?
It is technically possible to use WSL2 (Windows Subsystem for Linux), but it is not recommended for production builds due to problems with file system performance and access rights. Native Linux provides better stability and compilation speed.
How much disk space is needed to build Android 13?
The source codes require about 250-300 GB. Taking into account intermediate object code files during compilation, it is recommended to have a minimum of 400-500 GB of free space on a fast NVMe SSD.
What to do if the build throws a Java error?
Most likely, the JDK version does not meet the requirements of the Android version. Try switching the active version of Java via the command update-alternatives --config java to the required one (usually Java 8 or 11).
Where can I find a ready-made Device Tree for my phone?
Search on GitHub for "device [manufacturer] [model]" or on the XDA Developers forum in the development section of your device. Enthusiasts often post their work in the public domain.