Files with the extension .img are a fundamental element of the Android ecosystem, representing exact sector-by-sector copies of partitions of the device’s file system. The average user rarely has to deal with the need to work with such images, however, enthusiasts, developers and gadget repair specialists often look for ways how to open an Android img firmware file to extract data or modify system components. Understanding the structure of these files is critical for those who customize the operating system or restore bricked smartphones.
There is a misconception that the firmware image can be opened using standard tools of the Windows or macOS operating system, like a regular archive. In fact, the img file structure is adapted for Linux file systems (ext4, squashfs, erofs), which are not native to desktop OSes. To work correctly with them, specialized software is required that can emulate a reading environment or convert the structure into an understandable format. In this article, we will analyze in detail the tools and methods that allow you to safely interact with system images.
Before you begin manipulation, you must clearly understand the risks: incorrectly changing headers or partition tables can lead to complete inoperability of the device. Android Image Kitchen and console utilities provide powerful functionality, but require care. We will look at both graphical interfaces for beginners and advanced methods for experienced users seeking to gain full control over the firmware of their gadget.
Structure and features of Android image files
An image file img is not just a container with data, but a bitwise copy of a memory section. Depending on the purpose, inside there may be a system kernel (boot.img), recovery (recovery.img), a system partition with applications (system.img) or user data (userdata.img). Each type has its own specific formatting and protection. For example, modern versions of Android often use compressed file systems such as EROFS or SquashFS, which makes it difficult to directly access content without first decompressing it.
Structure analysis often requires a file header, which stores information about the size, file system type, and checksums. Tools like file in Linux or specialized HEX editors allow you to see this metadata. It is important to understand that an attempt to mount an image system_new.img from Android 13 on an outdated emulator may fail due to incompatibility of kernel versions and file system drivers.
⚠️ Attention: Never try to write a modified image back into the device memory without checking its integrity through a checksum (MD5 or SHA256). An error in one byte can make the bootloader inoperable.
Firmware developers often divide images into “sparse” (sparse) and full. Sparse images are used to save space when transferred over the network and require conversion to RAW format before editing. The utility simg2img is the de facto standard for performing this operation. Without this step, most content viewing apps simply will not recognize the file or will show an empty structure.
Before starting, always create a backup copy of the original .img file. To do this, use the dd command in Linux or the image creation function in Win32DiskImager.
Graphical utilities for unpacking and editing
For users who do not want to dive into the world of the command line, there are convenient graphical shells. Android Image Kitchenremains the most popular and functional tool. This app allows you to drag files boot.img or system.img into the application window and automatically unzip. The interface is intuitive: after processing, you get a folder with files that can be edited in any text or graphics editor.
The work process in Android Image Kitchen looks like this: the app determines the type of image, extracts the kernel (zImage or dtb), ramdisk (ramdisk) and root file system. After making changes, for example, adding root access or replacing system fonts, just click the “Repack” button to assemble all the components back into a single firmware file. This significantly speeds up the modding process compared to manual methods.
Another useful utility is Ext2Explore, which allows you to view the contents of ext2/ext3/ext4 file system images in the Windows environment. While it's not designed to fully write changes back to an image as conveniently as dedicated food processors, it's great for quickly extracting specific files such as libraries or configuration scripts. Just open the file .img through the app menu and navigate through the folders as in a regular Explorer.
It is worth noting that graphical tools may not correctly handle new compression formats introduced in Android 11 and higher. If the app gives an error when trying to open a file, it most likely requires updating the software itself or using the command line with the latest binaries. Always check the compatibility of the utility version with the version of Android whose firmware you are interested in.
Working with images via the command line and Linux
The most flexible and reliable way to interact with files .img is to use the Linux operating system or terminal emulators. Here the user has access to a full set of utilities, such as mount, unpackbootimg and mkbootimg. To get started, you need to install the android-tools-fsutils and simghelperpackages, which contain the necessary converters and mounting tools.
The procedure for mounting an image is as follows: first, a mount point is created in the file system, then the image is mounted as a virtual disk. This allows you to edit files directly using any text editors such as Nano or Vim. After completing the edits, the image will be carefully unmounted, saving all changes. This method guarantees minimal risk of damage to the file structure compared to multiple repacking.
sudo mkdir /mnt/android_imgsudo mount -o loop system.img /mnt/android_img
Editing files...
sudo umount /mnt/android_img
To work with boot images (boot.img), a script unpackbootimgis often used. It splits the image into separate components: the kernel, the second stage of the bootloader, the ramdisk, and the kernel parameters (cmdline). This is necessary if you want to replace the kernel with a custom one or implement init scripts at an early stage of boot. Reassembly is performed by the utility mkbootimg, where it is important to strictly observe the order of arguments and memory addresses specified in the original file.
⚠️ Attention: When using the mount command, make sure that you have superuser rights (root). Attempting to mount without the appropriate privileges will result in an access error and will not allow changes to be saved.
In the Windows environment, an analogue of mounting can be the use of the WSL2 subsystem (Windows Subsystem for Linux). It allows you to run a full Linux kernel inside Windows, giving you access to all of the above-mentioned utilities without the need to install a virtual machine or dual boot. This is a modern standard for developers working with Android on a PC running Windows.
☑️ Preparing to edit the image
Specialized tools for bootable images
Boot partition boot.img has a unique structure that is different from the system partition. It contains a compressed Linux kernel and a ramdisk image, which is mounted as the root file system when the device starts. Regular mounting is not suitable for working with it, since the content is packaged in cpioformat. This is where specialized unpackers come to the rescue, such as OSM Kitchen or MagiskBoot.
MagiskBoot - this is a tool that is part of the popular solution for obtaining root access Magisk. It can not only unpack and pack boot.img, but also patch the image to introduce root access, while maintaining the original bootloader signature (on some devices). This makes it an indispensable tool for modders. The command magiskboot unpack boot.img instantly extracts all the necessary components into the current directory.
The table below shows a comparison of popular tools for working with different types of images:
| Tool | Type of supported images | Difficulty of use | OS |
|---|---|---|---|
| Android Image Kitchen | Boot, System, Recovery | Low (GUI) | Windows |
| MagiskBoot | Boot, Vendor Boot | Medium (CLI) | Cross-platform |
| Ext2Explore | System, Userdata (ext4) | Low (GUI) | Windows |
| Mount (Linux) | Any block devices | High (CLI) | Linux / WSL |
When choosing a tool, you should focus on a specific task. If you just need to replace the boot logo or add a couple of libraries to the ramdisk, MagiskBoot will be the best choice. For deep processing of the system partition with replacement of applications, mounting or Android Image Kitchenmethods are better suited. There is no universal solution “for all occasions”, since device manufacturers often make their own changes to the image header format.
What is AVB and how does it affect editing?
Android Verified Boot (AVB) is a bootloader protection system that verifies the digital signature of partitions at startup. If you change the .img file without properly re-signing it with developer keys, the device may not boot or may go into Recovery mode. To bypass, you need an unlocked bootloader and disabled verification check (dm-verity).
Converting and working with sparse images
Many firmware distributed by manufacturers (especially Xiaomi, Google Pixel) use the format sparse image. These files take up less space by skipping empty blocks, but they cannot simply be mounted or opened in a HEX editor. The first step should always be to convert to a RAW image. To do this, use the utility simg2img, which is available as part of the Android SDK Platform Tools or as a separate binary file for Linux and Windows.
The conversion command looks extremely simple, but requires specifying the input and output files. After completing the operation, you will receive a full-fledged image, the size of which may significantly exceed the original file. You can already work with it using standard methods: mount, edit files, or pack it back using the utility img2simgif you plan to flash the firmware via Fastboot.
simg2img system_sparse.img system_raw.imgIt is important to consider that reverse conversion to sparse format is not always necessary. If you plan to flash your device using tools like the SP Flash Tool or Odin (for Samsung), you often need a RAW format or a manufacturer-specific format. Always check the firmware tool's documentation to understand what type of file it expects as input. An error at this stage may result in a failure to write to the phone's memory.
⚠️ Attention: When converting large images (more than 4 GB), make sure that the target drive is formatted with the NTFS or exFAT file system. The FAT32 file system does not support files larger than 4 GB, and the writing process will be interrupted with an error.
Some advanced users prefer to use automation scripts that perform a chain of actions: unpacking sparse, mounting, applying patches, unmounting and packing back. This reduces the chance of human error and saves time when processing files in bulk. However, such scripts require careful configuration of the paths to the executable files.
Converting sparse to raw is a mandatory step for editing system partitions of modern firmware. Without this step, access to the data inside the image is impossible.
Possible problems and methods for solving them
When working with files .img users often encounter a number of common errors. One of the most common is “Failed to mount image” or “Unknown filesystem type”. This usually means that the utility did not recognize the file system inside the image. In such cases, it helps to manually specify the FS type (for example, -t ext4) when mounting or using more recent versions of tools that support f2fs or erofs.
Another common problem occurs after packaging the image: the device does not turn on or freezes on the logo. This indicates a violation of the header structure or incorrect memory addresses during assembly boot.img. For diagnostics, it is recommended to use logs dmesg or logcat via an ADB connection, if the system is at least partially booted. Comparing the headers of the original and modified images through a HEX editor often helps.
It is also worth mentioning the problem of lack of disk space when unpacking. The system image can occupy several gigabytes, and when unpacked its size increases. Before starting work, make sure that there is free space on the system disk that is at least 1.5–2 times the size of the image. Ignoring this requirement will lead to an emergency termination of the app and possible corruption of temporary files.
Is it possible to open an .img file on a phone without a computer?
Direct editing of files .img on the device itself is extremely difficult and is not recommended due to the risk of locking the bootloader. However, there are terminal applications (such as Termux) that allow you to install Linux utilities and perform basic browsing or conversion operations if the phone is rooted. But for full modification and firmware you still need a PC.
Is it safe to edit system.img to remove ads?
Technically it is possible, but risky. Removing system applications can break the dependencies of other OS components, resulting in a cyclic reboot (bootloop). A safer alternative is to use ADB commands to disable applications (pm disable-user) without physically deleting files from the firmware image.
Which app is better for a beginner: Image Kitchen or MagiskBoot?
For beginners working in the Windows environment, Android Image Kitchen will be a more convenient choice thanks to graphical interface and no need to enter commands manually. MagiskBoot more powerful, but requires working through the command line and understanding the structure of the boot image.
Why did the file become larger than the original after editing?
When unpacking and repacking, compression algorithms may change or service data may be added, which increases the file size. If the device requires a strict partition size (for example, when flashing through a certain mode), it may be necessary to trim the file or use specific compression flags when building.
Do these methods support .ozip and .opp files?
Files with extensions .ozip (Oppo/Realme) and .opp are encrypted containers. Before applying methods for working with .img, they must be decrypted using special utilities (for example, oppo_decrypt). Only after decryption can you find standard images inside .img, suitable for editing.