Creating your own operating system based on Android

Developing your own operating system based on Android is a complex but exciting process that opens up endless possibilities for enthusiasts and developers. Instead of being stuck with stock firmware from manufacturers, you get full control over every aspect of your device, from the core system to the visual interface. This requires a deep understanding of the architecture, programming skills and patience, since the compilation process can take hours. Many people mistakenly believe that creation is just a matter of replacing wallpapers and icons. In fact, assembling a full-fledged Linux, programming skills and patience, as the compilation process can take hours.

Many people mistakenly believe that the creation custom firmware comes down to just replacing wallpaper and icons. In fact, assembling a complete ROM (Read-Only Memory) involves working with the source code AOSP (Android Open Source Project), modifying drivers and adapting the system to specific hardware. In this article, we will look at the key steps necessary to start your project to create a unique mobile platform.

Preparing the working environment and tools

The first step is organizing the right environment for development. The operating system Linux is the de facto standard for building Android, and most tools are optimized for it. Although it is theoretically possible to build in virtual machines on Windows or macOS, this often leads to compilation errors and significant performance degradation.

You will need a computer with a powerful processor and a large amount of RAM. Compiling source code is a resource-intensive task that can eat up to 100 GB of disk space. It is recommended to use an SSD drive to speed up the process of reading and writing thousands of small files.

⚠️ Attention: Tool versions are critical. Using an unsupported version of JDK (Java Development Kit) or Python will lead to errors in the early stages of repository synchronization. Always check the requirements in the official AOSP documentation before installing packages.

To work, you must install a basic set of utilities. In distributions based on Ubuntu or Debian this is done through the terminal. Make sure that you have git, repo, wget and compilers installed. Without these components, the build script simply will not run. gcc And g++. Without these components, the build script simply will not run.

Obtaining and synchronizing AOSP source code

The repository will be the basis of your future system. AOSP. It's a giant repository of code containing millions of lines. To manage such a volume of data, Google has developed a utility repothat allows you to synchronize many Git repositories at the same time. You will need to initialize the client and select a specific development branch corresponding to the version of Android you want to build.

The download process can take anywhere from several hours to a day depending on the speed of your Internet connection. It is important to ensure network stability, as a broken connection can damage data packets. After synchronization is complete, you will have a complete copy of the system on your disk, ready for modification.

• 📂 Initializing the repository with a command repo init -u https://android.googlesource.com/platform/manifest -b android-14.0.0_r1
• ⬇️ Synchronizing all branches through the command repo sync -c -j$(nproc --all)
• 🔍 Checking the integrity of downloaded files before starting the build
• 🔄 Regularly updating the local copy of the code to receive security patches

Choosing the right branch (Branch) determines the functionality and compatibility of your OS. New versions bring fresh features but may be less stable on older hardware. Old branches, such as Android 11 or 12are often more optimized for mid-range devices.

Adaptation for a specific device (Device Tree)

The most difficult stage is the creation Device Tree (device tree). The generic AOSP image does not contain drivers for your specific smartphone. You need to extract proprietary files (closed drivers, libraries, proprietary applications) from the stock firmware of your device and integrate them into the build.

To do this, use a tool extract-filesthat automatically copies the necessary binary files from the connected phone or firmware dump. However, manual editing of configuration files, such as BoardConfig.mk and device.mk, is often required. Kernel parameters, memory sections and features of the hardware platform are specified here.

Configuration file	Purpose	Criticality
BoardConfig.mk	Kernel parameters, architecture, sections	Critical
device.mk	List of copied files and applications	High
AndroidProducts.mk	Determination of the name of the assembly product	Medium
system.prop	System properties and tweaks	Medium

Errors in settings Device Tree lead to a “bootlap” (cyclic reboot) or lack of communication, camera and sound. It is necessary to carefully study the logs of other developers who have already ported systems to similar processors, for example, Snapdragon or MediaTek.

Where can I get proprietary files?

They can be extracted directly from a working smartphone with root access or download a ready-made dump of stock firmware from the XDA Developers forums. Using files from a different model, even with the same processor, can lead to unstable operation.

Compiling the kernel and creating a system image

The kernel (Kernel) is the heart of any operating system. For Android, a modified Linux kernel is most often used. You can use the pre-installed kernel from the AOSP sources or compile your own, adding support for specific features such as processor overclocking or new file systems.

The compilation process is started by the build script. Depending on the power of your PC, this may take from 30 minutes to 3 hours. The result will be several image files: boot.img (kernel and ramdisk), system.img (main system), vendor.img (drivers) and recovery.img (recovery mode).

⚠️ Attention: Never use a kernel from one model on another, even if the processors identical. Differences in power and display controllers can lead to physical damage to the device or immediate failure.

After successful compilation, you must sign the images with digital keys. Without a signature, the bootloader (Bootloader) of most modern smartphones will refuse to install the system. For test builds, test keys are often used that come with the source code.

Testing and debugging the finished firmware

Before installing it on the main device, it is highly advisable to test the assembly in emulator Android Studio or on a cheap test smartphone. This will allow you to identify critical errors without the risk of “bricking” your main gadget. The emulator is useful for testing the interface, but cannot reproduce the operation of specific hardware, such as a modem or sensors.

If you are ready to flash a real device, make sure that the bootloader is unlocked and a custom recovery is installed, for example TWRP. The installation process usually occurs through the Recovery menu in the format zip or through the mode fastboot using commands fastboot flash.

If the boot is unsuccessful, you must use logs logcat and dmesg to find the cause of the failure. Often the problem lies in incorrect file access rights or the absence of the required library in the section /system. The iterative process of “build-test-fix” is the basis of development.

Publishing and supporting a custom OS

When your system is stable, you can think about distributing it. Placing the firmware on forums like XDA Developers or in Telegram channels requires detailed documentation. Users must clearly understand which features work and which have limitations. Specify the Android version, build base (for example, LineageOS or AOSP) and a list of known bugs.

Project support is a continuous process. You will have to release security updates, fix bugs found by the community, and adapt the system to new versions of Android. Open source means that other developers can use your work, which speeds up the development of the project.

Remember that creating your own OS comes with responsibility. Poor firmware can create vulnerabilities in the security of user data. Always audit your code and check the integrity of files before publishing.

How long does the first build of Android take?

On a modern computer with an SSD and 32 GB of RAM, the first full build takes from 2 to 4 hours. Repeated builds (incremental) are faster, since only changed files are compiled, and can take 15-30 minutes.

Do you need to know Java to create firmware?

Yes, knowledge of Java is required, since most of the Android framework is written in it. You will also need skills in working with C/C++ to modify low-level components and the kernel, as well as Bash to write build scripts.

Is it possible to build Android without an unlocked bootloader?

No, it is not possible. The bootloader verifies the digital signature of the system. Without unlocking it, you will not be able to install an unsigned recovery or a custom system image. Unlocking usually erases all data from the device.

What are GApps and do you need to embed them?

GApps (Google Apps) is a package of Google applications (Play Market, Gmail, Maps). Pure AOSP does not have them due to licensing restrictions. You can embed them into the assembly or offer the user to install the package separately through recovery after flashing the firmware.

Is it dangerous to test your builds on the main phone?

Yes, it carries risks. An error in the kernel or driver code can lead to a software “brick” that requires complex recovery via EDL mode, or even to physical overheating of components. Always have a spare device on hand for tests.