Creating your own firmware for a Xiaomi device is not just a way to change the logo when you download, but a full immersion in the Android architecture. Many enthusiasts are looking to modify system files to remove preinstalled software, optimize power consumption or add features that are not available in stock MIUI and HyperOS. This process requires care, but opens up limitless possibilities for managing the device.
Before you start compiling code or porting, you need to be aware of the risks. Any interference with the bootloader and system partition can lead to the inability to start the operating system. Backing up all important data is the first and most critical step, without which you can absolutely not start. In this article, we will discuss the ways from simple modification of finished images to deep customization.
There are several levels of firmware complexity. You can use automated builders that generate a stock-based image by removing redundant components. A more advanced option is to port firmware from one device to another, which requires a deep understanding of partition structure. The most difficult level is to build AOSP (Android Open Source Project) for a specific hardware that requires knowledge of C++ and Python.
⚠️ Warning: Building and installing unverified images on your own can cause warranty loss and the device to fail.
To start working, you will need a computer with Windows or Linux operating system, as well as a high-quality computer. USB-A stable connection is critical, because a flashing interruption can lock the bootloader permanently, and you should also pre-installe all the necessary drivers for your processor, whether it's Snapdragon or MediaTek.
Preparation of tools and development environment
The foundation for any firmware work is a properly configured environment. You'll need to install Android SDK Platform Tools, which contain adb and fastboot utilities. Without them, low-level communication with your phone is impossible. For Windows users, Qualcomm or MediaTek drivers are also critical, which are often installed separately from the main software.
Magisk is often used to modify system images, allowing you to obtain superuser rights without changing the system partition, creating a so-called systemless environment, which makes it easier to roll back changes in case of errors. To work with firmware archives (.zip) and images (.img), you will need specialized utilities such as Android Image Kitchen or MT Manager.
☑️ Firmware readiness check
If you're planning to do serious porting, you'll need a virtual machine with Linux (often Ubuntu) and a set of compilers installed. kernel and HAL-level assembly (Hardware Abstraction Layer) require significant computing resources. For a user who just wants to customize the interface, a PC and a set of basic utilities are enough to unpack system images.
Unlocking the loader and obtaining rights
The first obstacle to creating your firmware is a locked bootloader. Xiaomi has implemented a strict security policy that requires official unlocking through Mi Unlock servers, which requires you to link your Mi Account to the device and wait a certain period, which can be from 7 to 168 hours.
The unlocking process completely clears the device's internal memory, so re-backup is mandatory. Once successfully unlocked, the boot boot boot, recovery and system will be labeled Unlocked, which gives access to the boot, recovery and system partitions, which are the parts we'll be modifying to create our own version of the OS.
- 🔓 Download the official Mi Unlock Tool utility from the developer site.
- 📱 In the phone settings, turn on “For developers” and activate “Factory unlocking».
- ⏳ Wait for the waiting timer to expire in the application "Mi Unlock Status».
- 💻 Run unlock through PC by clamping volume buttons at the same time.
⚠️ Note: After unlocking the bootloader, some high-security banking applications and services may stop working due to a breach of TrustZone security integrity.
Root rights are usually obtained by running a modified boot.img image through the Magisk patch, which allows for changes to the system on the fly, but a full firmware often requires replacing the entire system or vendor partition, making it a must.
What are A/B sections?
Analysis of stock firmware structure
Before you change anything, you need to understand what the firmware is made of. Xiaomi images are usually distributed in.zip (for Recovery) or.tgz (for Fastboot). Inside the Fastboot archive are raw partition images: boot.img, system.img, vendor.img, dtbo.img The most interesting parts for modification are system and vendor.
To work with the Android file system, which often uses ext4 or f2fs format, you need tools to unpack and package images. Standard Windows tools do not open these files. Utilities like EXT2FSD or built-in Linux features allow you to mount the image as a disk and access files.
The key file to analyze is build.prop, which is located at the root of the system partition, and it contains device identification, screen settings, audio codecs, and more, and by changing the values in this text file, you can globally change the behavior of the system, for example, make the phone think it has more RAM or another DPI screen.
| Section | Description | Can I change? |
|---|---|---|
| boot | Core and init scripts | Only with caution. |
| system | Main OS and applications | Yes (main purpose) |
| vendor | Equipment drivers | Only experienced. |
| recovery | Reconstruction regime | Replaced with TWRP |
System modification and removal of bots
The most popular scenario for creating your own firmware is to clear the runoff from ads and pre-installed applications. Once you unpack the system.img image, you get access to /system/app and /system/priv-app directories. That's where the system applications are, which can't be removed in the normal way.
When deleting files, it's important to keep the folder structure in mind. APK-file, the system may not boot or go to bootloop. it is recommended to replace the deleted stub applications with empty ones APK-files with the same name and signature, or use installer scripts that do so automatically when you first start.
This is also where localization is done, where you can replace the resources in the /system/framework folder or specific application resources to change fonts, icons or interface lines, and this allows you to create a unique visual shell without changing the system engine. Tools like APK Editor are often used to replace graphic elements.
⚠️ Warning: Never remove critical system components such as PackageInstaller, Settings or SystemUI without an accurate understanding of their function.
Once all the changes have been made, the image needs to be properly packaged back. It is important to keep the file's permissions. If executable files lose the execution bit and configuration files lose the read rights, the system will not be able to use them. Packaging tools usually offer a "save rights" option that must be activated.
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Keep the originals. APK-files of the deleted applications in a separate folder on the computer. If a critical error is detected after firmware, you can quickly return the file to its place and reassemble the image.
Porting firmware from other devices
Porting is the process of adapting firmware built for one device (donor) to work on another (recipient) -- this is the top aerobatics in the Xiaomi modding world. The main challenge is that the kernel and drivers are compatible. The processors must be identical or as close to the architecture as possible.
The process starts with replacing files in the boot and vendor section with files from the recipient device. The kernel from the donor won't work because it doesn't know how to control your screen, camera, or sensor specifically. However, system files can often be taken from a newer device to get a fresh Android on an older phone.
A critical step is to edit the script updater-script (for Recovery) or flash_all.bat (It's a device model check, and if you don't remove those checks, you'll miss the installation, and you'll often need to edit the fstab configuration files that describe the disk layout.
- 📂 Extract. boot.img and vendor_boot.img from your phone's stock firmware.
- 🔄 Take it. system.img from the firmware-donor (desired version of Android).
- 🛠 Replace the core and vendor in the firmware-donor with your stock.
- 📝 Edit the installation script by removing the model verification (assert).
Often ported firmware has bugs: the camera, Bluetooth or proximity sensor may not work, due to incompatibility of binary drivers (blobs), which require deep knowledge of kernel compilation and.so library swapping, which is often more difficult than the installation itself.
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Successful porting depends on 90% of the hardware platform’s similarity, and porting firmware between phones on different processors (e.g., Snapdragon to MediaTek) is almost impossible.
Assembly and installation of a custom image
When the modified image is ready, it needs to be packaged properly. If you've been working with a file system, use the command make_ext4fs Or a similar utility in your toolkit to create the final system.img. The image size should not exceed the partition size on the device, otherwise the installation will end in error.
Installation is done via Fastboot mode or custom TWRP recavers. In the case of Fastboot, commands look like fastboot flash system.img. This method is more reliable, since bypass is many checks that can be found in Recovery. However, it requires an unlocked bootloader.
fastboot flash boot boot.img
fastboot flash vendor_boot vendor_boot.img
fastboot flash system system.img
fastboot rebootThe first launch after installing custom firmware may take 5 before 15 The system is optimizing applications (ART If the phone is stuck on the logo more than on the 20 In the minutes, there's probably a compatibility error or data corruption, and then you need to log in to Recovery and make Wipe. Data/Factory Reset.
⚠️ Warning: If the phone doesn’t turn on and respond to buttons after firmware, you may need to enter mode EDL (Emergency Download Mode for recovery via MiFlash in Clean All mode.