Creating an IMG image on Android: a complete guide

Creating IMG of the image on an Android device is a powerful tool that is often needed by enthusiasts, developers and advanced users. Such a file is a bit-by-bit copy of a memory section, be it the entire system disk, the boot sector, or a specific data section. Unlike conventional application backups, a system image allows you to restore the device to its original state even after critical failures when the phone stops booting.

The process of creating an image can pursue different goals: from preserving the current working firmware before experiments to transferring the entire system to another device with a similar architecture. It is important to understand that working with images requires root access an unlocked bootloader. Without these privileges, access to low-level memory sections will be blocked by the Android security system.

In this article we will examine in detail several methods for creating images: from using custom recovery TWRP to working with console utilities via a computer. You will learn not only to create files, but also to understand their structure, as well as securely manage the resulting data. Remember that any manipulation of partitions carries risks, so you should carefully follow the instructions.

Preparing the device and necessary tools

Before you start creating the image, you need to ensure a stable working environment. The main requirement is to have superuser rights. If your device is not yet rooted, you will need to find a suitable method for your model, since standard Android tools do not allow low-level memory reading.

The second critical element is free space on the storage device. IMG files can take up a significant amount of space equal to the size of the copied partition. For example, a partition image system often weighs from 2 to 4 GB. It is recommended to use an external microSD card or connect to a computer to save data directly so as not to fill the internal memory.

You will also need a set of tools for connecting with a PC. Install the package Android SDK Platform-Toolsthat contains the utilities adb and fastboot. Without them, executing commands from the terminal will be impossible. Make sure that the drivers for your smartphone are installed on your computer, otherwise the device will not be detected in debugging mode.

⚠️ Attention: Before starting work, be sure to back up important personal data (photos, contacts) to the cloud. The image creation process itself is safe, but the preparatory steps (unlocking the bootloader) can lead to complete deletion of data from the device.

Method of creating an image through custom recovery TWRP

The most accessible and visually understandable way to create a backup copy of partitions is to use a custom recovery such as Team Win Recovery Project (TWRP). This method does not require entering complex commands and minimizes the risk of user error thanks to the graphical interface.

After booting into recovery mode, go to the section Backup. Here you will see a list of available sections for reservation. To create a complete image of the system, you usually choose Boot, System and Data. Selecting a partition Cache or Dalvik is not necessary, since they can be generated anew, but this will increase the process time.

An important step is choosing a save location. In the backup settings (Storage) specify an external SD card. This will prevent the internal memory from becoming full and will speed up recording. After pressing the swipe button to confirm, the memory dump process will begin, which can take from 5 to 20 minutes depending on the amount of data and speed of the memory card.

The resulting files in the folder TWRP/BACKUPS are technically archives containing IMG images. If necessary, they can be extracted on the computer to obtain clean files .img for further work with firmware utilities.

Creating an image through the terminal and the dd utility

For those who prefer complete control over the process, the ideal solution is to use a console utility dd. This command allows you to create bitwise copies of memory blocks directly. To perform it, you will need a terminal emulator on the device itself (for example, Termux) or a connection via adb shell from a computer.

The first step is to determine the exact paths to the partitions. On Linux-like Android systems they are located in the /dev/block/directory. However, block names may differ between devices. To find the desired partition, run the command ls -l /dev/block/platform/*/by-name. You will see a list of links where, for example, boot points to a specific block file.

The image creation command itself looks like this:

dd if=/dev/block/bootdevice/by-name/boot of=/sdcard/boot.img bs=4096

Here the parameter if indicates the source (input file), of —the destination (output file), and bs sets the block size to speed up reading. By replacing boot with system or recovery, you can create an image of any available partition.

Deciphering the parameters of the dd command

The 'if' parameter means Input File - this is the path to the device that we are reading. The 'of' parameter is the Output File where the result is written. 'bs' (block size) specifies the block size; the standard value of 4096 bytes is optimal for balancing speed and processor load. An error in the path may result in an empty file being written or a crash.

After the process is completed, be sure to check the integrity of the file. The size of the created IMG image must match the size of the partition. If the file weighs 0 bytes or significantly less than expected, it means that the path to the source was specified incorrectly or the process was interrupted.

Working with images via a computer and Fastboot

An alternative approach involves creating an image directly on the computer using the Fastbootmode. This method is convenient because it does not require free space on the smartphone, since the data is transferred directly to the PC’s hard drive.

To do this, put the device into bootloader mode (usually by holding the power and volume down buttons) and connect it to the PC. Enter the command fastboot devices to test the connection. If the device is displayed, you can start reading partitions.

The command to remove an image looks like this:

fastboot flash:raw boot boot.img

However, it is worth noting that the standard fastboot is more often used for Records images, not reading. Reading via fastboot is not supported on all devices and often requires specific flags or modified versions of the bootloader. Therefore, method c dd Inside Android is often more universal.

Section	Description	Approximate size	Criticality
boot	Kernel and ramdisk	16–64 MB	High
recovery	Recovery mode	16–64 MB	Medium
system	OS and application files	2–6 GB	Critical
userdata	Personal user data	Depends on filling	Critical
cache	Temporary files	100–500 MB	Low

Compression and optimization of the resulting images

Raw IMG filesobtained by the ddmethod often contain a lot of empty space, especially if we are talking about partitions with a file system that has not been completely filled. This leads to inefficient use of space when storing backups.

For optimization, you can use compression utilities such as gzip or lz4. On a computer, this is done with the command gzip boot.img, which will reduce the file size several times. However, for subsequent firmware, such a file will need to be unpacked first.

There is also a method of “cropping” the image. Using the utility img2simg you can convert a raw image into the sparse image format, which is used by Android to save space when recording. This is especially true for the section system.

Some users prefer to mount images as virtual disks in order to extract individual files from them without restoring the entire system. In a Linux environment, this is done through the command mount -o loop, and in Windows - using specialized drivers or emulators.

⚠️ Attention: Never try to mount or edit a partition image boot or recovery without deep knowledge of the Android structure. Changing the header or kernel may make the image unbootable.

Restoring the system from a created image

The main purpose of creating a backup is to allow for quick recovery. If you created the image via TWRP, the return process is simple: boot into recovery, select Restore and indicate the desired backup date.

If you have a separate .img file, you can flash it via fastboot. Connect your phone in bootloader mode and enter the command:

fastboot flash boot boot.img

Replace boot with the partition name corresponding to your file. After flashing the firmware, be sure to run the command fastboot reboot.

In cases where the device does not enter Fastboot mode, you can use the utility dd in the opposite direction from the terminal on the device (root required):

dd if=/sdcard/boot.img of=/dev/block/bootdevice/by-name/boot

This method is extremely dangerous: an error in one letter of the path of may erase important data irrevocably.

Common errors and ways to resolve them

When working with images, users often encounter the “No space left on device” error. This happens when the internal memory is full and you try to save the image there. Always use external media.

Another common problem is hash sum mismatches. If after flashing the device the device goes into bootloop (cyclic reboot), the image may have been damaged during recording or downloading. Use the command md5sum to check the integrity of files.

It is also worth considering differences in memory layout between different manufacturers. The image from OnePlus is not suitable for Xiaomi even with the same version of Android. The processor architecture and partition table must match.

⚠️ Attention: Recovery interfaces and partition names may differ depending on the Android version and device model. Always check the documentation for your specific model before executing write commands.

FAQ: Frequently Asked Questions

Is it possible to create a complete image of the entire memory with one file?

It is technically possible to copy the entire block /dev/block/mmcblk0, but this will create a huge file size (equal to the size of the entire flash memory, for example 64 GB or 128 GB), most of which will be empty. It is more efficient to create images of individual partitions (system, boot, data).

Do you need to turn off the Internet when creating an image?

It is advisable. If while creating an image of a partition data you receive a message or an application is updated, the file system may change on the fly, which will lead to the creation of a broken or inconsistent image.

What is the difference between .img and .zip firmware?

IMG is a sector-by-sector copy of the partition, ready for direct memory write. ZIP is an archive containing the installation script (updater-script) and files that are unpacked and copied to the required locations by the installation script. IMG is a lower-level format.

Is it safe to edit an IMG image on a PC?

Yes, but only if you know what you are doing. To edit system files inside the image, it must be mounted in the OS. Changing critical libraries may cause the phone to stop booting.

How to open an IMG file on a computer?

In Windows, this is difficult to do using standard tools. It is better to use apps like OSFMount or Win32 Disk Imager. In Linux and macOS, the image can be mounted into a folder with the command mount and viewed as a regular folder.