Owners of Android devices are often faced with software imposed by the manufacturer, which cannot be removed using standard methods. Editing the firmware allows you to cut out system junk, optimize power consumption and unlock the hidden capabilities of the processor. This process requires a deep understanding of the file system structure and caution, but the result is worth it.
There are two main approaches to modification: building from scratch from source code (AOSP) or modifying stock ones system imagesprovided by the manufacturer. The second option is more common among enthusiasts, as it retains all the specific camera and modem drivers. The process begins with obtaining root access root and unlocking the bootloader bootloader.
Before making changes, you need to create a full backup of the current state of the device via TWRP Recovery. Any mistake when editing system partitions can lead to the smartphone turning into a “brick”. Data security and hardware performance depend on the accuracy of your actions at each stage.
Preparation of tools and analysis of the image structure
To work with firmware images, you will need specialized software for your PC. The main tool for working with images system.img and vendor.img is the utility Android Image Kitchen or scripts based on Python. These apps allow you to unpack the image, extract the file system and assemble it back without losing boot attributes.
The downloaded firmware file (usually in the format .zip for OTA or .tar for Odin) must first be unpacked with an archiver. Inside you will find many files with the extension .img. We are interested in the sections systemcontaining applications and frameworks, and bootwhere the kernel is located. Editing the kernel is a separate complex topic, so beginners are advised to limit themselves to the section system.
⚠️ Attention: Never try to edit the section
userdataorcachedirectly in the firmware image. These partitions are generated dynamically when the device is first booted and contain personal data that should not be hardcoded into the image.
Load the image system.img into the unpacking app. The process can take anywhere from 5 to 20 minutes depending on the file size and the speed of your hard drive. Once completed, you will receive a folder with the complete Android directory structure, including app, priv-app and framework.
It is important to understand the difference between user applications and system applications. Removing critical components from the folder framework will lead to bootloop (cyclic reboot). Always check dependencies before removing any system package.
Use Notepad++ or VS Code to edit configuration files (.prop, .xml), since regular Notepad can break the encoding and damage the file.
Removing system garbage and bloatware
The main purpose of editing is to clean the system from preinstalled software. In the unpacked folder, go to the directory /system/app i /system/priv-app. The installation packages of all system applications are stored here. You can safely remove social network clients, games and services imposed by your telecom operator.
However, simply deleting the application folder is not enough. You must also delete the corresponding files .odex and .vdexif they are located in a separate folder oat inside the image archive. The presence of these files without the main APK file will cause a verification error when loading the system.
- 🗑️ Delete only those applications whose purpose you fully understand.
- 🔍 Check for dependencies: some Google services require them Google Services Framework.
- 📂 Maintain the folder structure: do not delete the directories themselves, only their contents.
Pay special attention to the file build.proplocated in the root of the unpacked system. This is a configuration file that manages device identification and various tweaks. By changing the settings in this file, you can trick apps into thinking you have a more powerful smartphone.
For example, changing the line ro.product.model can unlock high-resolution screen recording features or enable performance mode in games. But careless editing of this file is the most common reason why the phone stops booting after flashing the firmware.
List of applications safe to delete
You can delete: Email (stock), Calculator, Clock, Gallery (if you install a third-party one), Music. You cannot delete: Package Installer, Settings, SettingsProvider, Telecom, TelephonyProvider.
Optimizing power consumption and performance
After cleaning the system, you can begin fine-tuning the kernel and task scheduler parameters. This is done by editing the configuration files in the folder /system/etc or by introducing initialization scripts. Correct configuration allows you to increase battery life by 15-20%.
One of the effective methods is to disable unused daemons and services. In the file init.rc or its analogues you can find services that start when the system starts. By disabling logging services (logd) or debugging daemons, you will reduce the CPU load in the background.
| Parameter | Default value | Optimized value | Effect |
|---|---|---|---|
ro.min_freq |
Depends on the CPU | Increase the minimum frequency | Eliminate interface micro-lags |
vm.swappiness |
60 | 10 | Reduce page file usage |
persist.sys.ui.hw |
false | true | Hardware UI acceleration |
It is also worth paying attention to memory management. Editing the file lowmemorykiller.xml allows you to configure the thresholds for killing background processes. If you have a lot of RAM (8 GB or more), you can allow the system to keep more applications in the background without aggressively killing them.
Don't forget that aggressive optimization can lead to unstable operation of some applications. For example, a value that is too low swappiness can cause heavy games to crash if there is not enough physical RAM. Test the changes gradually.
☑️ Check before assembly
Modification of the graphical interface and fonts
Changing the appearance of the system is the most creative part of the process. You can replace standard fonts, icons, notification sounds, and even loading animations (bootanimation). All these resources are stored in the folder /system/media or /system/fonts.
To replace fonts, just copy the files .ttf to the appropriate directory, observing access rights. It is important that the file names match the original ones, otherwise the system will not be able to pick them up. A popular practice is to install fonts with better readability, such as Roboto Flex or custom styles.
⚠️ Attention: The file
DroidSansFallback.ttfis responsible for displaying hieroglyphs and special characters. Removing it or replacing it with an incorrect file will result in you seeing squares all over the menu instead of text.
Replacing the loading animation requires converting the sequence of images into a format that the loader can understand. Typically this is a set of PNG files packed into an uncompressed archive. The folder with the animation should be named bootanimation and placed in /system/media.
You can also modify resource files framework-res.apk and SystemUI.apk. This allows you to change the color of the notification bar, the shape of the battery icons, and the transparency of interface elements. A tool is used to decompile these APK files. APKTool.
Any changes to graphic resources increase the size of the system image, but do not affect performance unless heavy real-time animations are used.
Building the image and checking integrity
After making all changes, you need to assemble the modified files back into the image system.img. In the Android Image Kitchen app, click the Repackbutton. The build process is critical: it is necessary to preserve the original file system parameters, such as type (ext4, erofs) and block size.
If the build parameters differ from the original, the device bootloader may refuse to flash this partition, producing a signature or size error. Modern devices with verification AVB (Android Verified Boot) also require re-signing the image with cryptographic keys.
To bypass signature verification on many devices, it is enough to disable verification in the bootloader or use a custom recovery that ignores integrity verification. However, on devices with a locked bootloader, this cannot be done without exploits.
Check the size of the resulting image. It should not exceed the size of the original partition allocated by the manufacturer. If the image is larger, you will have to remove more system components or compress the data more.
Installing modified firmware
The final stage is installing the assembled image on the device. Switch your smartphone to mode Fastboot or boot into custom recovery TWRP. In Fastboot mode, use the command to flash the image:
fastboot flash system system.imgIf you are using TWRP, simply copy the file system.img to a memory card or internal memory and use the function Install Image, selecting the partition System. After completing the procedure, be sure to run the command Wipe Cache/Dalvik.
The first boot after installing custom firmware can take up to 5-10 minutes. The system will optimize applications and rebuild the cache. If the phone is stuck on the logo for more than 15 minutes, there was probably an error when editing files.
⚠️ Attention: If the device goes into an endless reboot, do not panic. Boot into recovery mode and restore the full backup (NANDroid backup) made before starting all manipulations.
Successful booting of the system means that the modification was successful. Now you can enjoy pure Android without unnecessary software and with optimized settings. Check security updates regularly, as a modified system may not receive them automatically.
What to do if fastboot does not see the device?
Install ADB/Fastboot drivers for your OS. Try a different USB port (preferably USB 2.0). The phone may require USB debugging confirmation, even in Fastboot mode on some models.
Is it possible to edit the firmware without unlocking the bootloader?
No, in most modern cases this is not possible. A locked bootloader verifies the digital signature of all partitions. Any change to the image will break the signature and the phone will refuse to boot. Unlocking the bootloader is required.
Will the warranty be void after editing the firmware?
Yes, unlocking the bootloader and modifying the system partition usually voids the manufacturer's warranty. In addition, on some devices (for example, Samsung), a Knox counter is triggered, which physically blocks the operation of some functions forever.
How to get everything back if something goes wrong?
The only reliable way is to use a previously created full backup (NANDroid) in Recovery mode. If there is no copy, you will have to look for stock firmware for your model and flash it through official utilities (Odin, MiFlash, SP Flash Tool).
Is it safe to remove Google Play Services?
It is strictly not recommended. Removing Google services will disrupt the operation of almost all applications that require authorization, push notifications, and geolocation. The system may become unstable or may not boot at all.