Data loss due to unsuccessful flashing of a smartphone is a nightmare for any owner of an Android device. Imagine the situation: you decided to update the system or install custom firmware, the process did not go according to plan, and as a result the device turned into a “brick”. The worst thing is when unique partitions disappear along with the operating system, such as EFS or Persistcontaining IMEI and sensor calibrations. It is almost impossible to restore them without a preliminary backup, which makes the procedure for creating a backup copy critical.
There are many ways to save the contents of your gadget’s memory, from the built-in functions of cloud services to a low-level dump via a computer. However, standard methods often save only contacts and photos, ignoring the very structure of the system. For complete security, you need to create Nandroid backup or a complete dump of partitions, which will allow you to roll back the device to its original state in the event of a fatal failure. Below we will discuss in detail the methods available to both ordinary users and advanced enthusiasts.
⚠️ Attention: Any manipulation of system partitions carries the risk of losing the warranty. If your device is under warranty service, make sure that unlocking the bootloader will not lead to the service center refusing to repair it.
Preparing the device and choosing a backup method
Before you start cloning system data, you need to make thorough preparations. The first step is always to free up space on the media, since the full firmware image can take up from 4 to 16 GB depending on the smartphone model. It is recommended to use an external memory card microSD or connect the device to a PC if the selected method supports direct data transfer.
The second important aspect is the battery level. The dump process can be energy-intensive, especially when using recovery where the screen often remains on. Make sure that the charge is at least 60-70% to avoid a sudden power outage in the middle of writing memory sectors.
It is also worth deciding on the tools. For users with an unlocked bootloader, custom recovery will be the best choice, while owners of stock devices can use utilities from the manufacturer or console commands ADB. The choice depends on your technical training and goals: a full backup for experimentation or saving critical data before sale.
☑️ Preparing to create a backup
Do not forget that different models have different memory layouts. On modern devices with data encryption, access to some sections may be limited without prior decryption or specific rights root. Therefore, there is no universal “one-click” solution, and each case requires an individual approach.
Creating a Nandroid backup through custom recovery TWRP
The most reliable and popular way to create a complete copy of the system is to use a custom recovery, such as Team Win Recovery Project (TWRP). This method creates a sector-by-sector copy of all selected partitions, allowing you to restore the device in the future exactly to the state in which it was at the time of backup.
First, you need to boot into recovery mode. This is usually done by using a combination of the volume and power keys while the device is turned off. In the TWRP menu, select Backup. Here you will see a list of available sections for reservation. It is critical to select not only System and Data, but also hidden partitions such as EFS, Modem and Persist.
⚠️ Attention: EFS and Persist partitions contain unique device identifiers. Their loss can lead to inoperability of the mobile network and sensors, which cannot be corrected programmatically without the original dump.
After selecting partitions, swipe to confirm the start of the process. The speed of creating a copy depends on the amount of data and the speed of the memory card. Upon completion of the operation, the files will be saved in the folder /sdcard/TWRP/BACKUPS/. It is recommended to immediately copy this folder to your computer or cloud storage, as the memory card may fail.
Rename the backup folder immediately after creation, adding the date and firmware version to the name. This will help avoid confusion if you make several backups at different times.
Using the ADB utility to create a full dump
If installing a custom recovery is impossible or undesirable, you can use the official tool from Google - Android Debug Bridge (ADB). This method requires a computer and an installed set of drivers, but it works even on devices with a locked bootloader, although with some limitations.
To create a full backup, use the command adb backup. Connect your smartphone to the PC, make sure that the debugging confirmation appears on the device screen, and enter the following command in the computer terminal:
adb backup -apk -shared -all -system -f backup.abThis instruction will create a file backup.abcontaining application data, system settings and the contents of the internal memory. However, it is worth noting that this method does not create a bit-by-bit copy of partitions like TWRP, and recovery may require additional format conversions .ab to .tar.
For more advanced users with root access, a direct dump of partitions is available via the command dd. This allows you to copy any block of memory, such as a bootloader partition. The command is executed directly in the device shell:
adb shellsu
dd if=/dev/block/mmcblk0p1 of=/sdcard/boot.img
Here it is important to know exactly the names of the block devices, which may differ on different processors (Qualcomm, MediaTek, Exynos). An error in the device name can lead to overwriting of data, so use the command ls -l /dev/block/by-name to view the current markup before starting work.
Specifics of working with MediaTek and Qualcomm processors
The processor architecture plays a key role in choosing a backup tool. Devices based on chipsets MediaTek often allow you to create complete firmware dumps using the utility SP Flash Tool in “Readback” mode. This method does not require superuser rights on the smartphone itself, but requires the presence of a scatter file (Scatter file), which describes the device's memory card.
In SP Flash Tool you need to go to the tab Readback, add a new region and specify the path to save the file. After connecting the switched off phone (sometimes you need to hold down the volume buttons), the process of reading the memory will begin. The resulting file will be an exact copy of the flash memory, which can later be used for recovery using the same tool.
For processors Qualcomm the situation is a little more complicated. A standard tool QPST or utilities like QFIL are more often used for flashing, but also support backup functions if compatible drivers and mode Emergency Download Mode (EDL) are available. Entering this mode often requires closing special contacts on the board or using an engineering cable.
| Platform | Main tool | Requirements | Risk level |
|---|---|---|---|
| MediaTek | SP Flash Tool | Scatter file, drivers VCOM | Medium |
| Qualcomm | QPST / QFIL | EDL mode, Firehose bootloader | High |
| Universal | TWRP Recovery | Unlocked bootloader | Low |
| Google ADB | Command line | USB debugging, ADB drivers | Low |
Owners of devices based on Samsung with Exynos processors should pay attention to the utility Odin. Although it is for firmware, combination with tools like SamFw allows you to read certain sections, however, a complete dump of user data via Odin is not possible due to brand security policies.
What is a Scatter file?
Scatter file is a text document containing the starting addresses and sizes of all memory sections for devices MediaTek. Without this file, the firmware tools don't know where to write or read data from. It can be extracted from the official firmware or using special utilities on a device with root access.
Saving critical EFS and IMEI partitions
Saving the partition EFS (Encrypted File System) deserves special attention. This section stores information about IMEI, Wi-Fi and Bluetooth MAC addresses, as well as radio module calibration data. Damage to this partition during flashing results in the phone no longer seeing the SIM card, and restoring IMEI using legal methods becomes impossible.
Most modern custom recovery automatically includes this section in the backup if the full backup option is selected. However, to be on the safe side, you can use specialized applications from Google Play, such as EFS Professional or IMEI Backup & Restore. These utilities create a separate backup file, which is convenient to store in the cloud.
⚠️ Attention: Never try to restore an EFS partition from another phone! The IMEI must be unique for each device. Using someone else's IMEI is illegal and may result in your device being blocked by carriers.
If you are using the dd ADB method, the command to save this partition will look specific to each model. For example, for many Samsung devices the path will be /dev/block/mmcblk0p18, but for Xiaomi it may be different. Always check the current paths in the documentation for a specific model or on specialized forums.
The EFS partition weighs only a few megabytes, but its loss makes the smartphone useless for calls. Make a backup copy of it as a separate file and store it in three different places.
Restoring data from a backup copy
The Restore process is almost the same as the process of creating a backup, but requires even more care. In the TWRP environment, just go to menu Restore, select the desired backup folder and mark the partitions for recovery. The system will warn you that the current data will be overwritten.
When restoring via ADB, the command is used adb restore, however, it does not work with all file types and often requires that the device does not have a lock screen installed or that it is unlocked at the time of recovery. Format files may require conversion to .ab may need to be converted to .tar using third-party scripts on a PC before unpacking.
Recovery via SP Flash Tool or Odin is performed in recording mode (Download/Flash). It is critical here not to confuse files and memory addresses. An error when restoring the boot loader image or partition table can lead to a complete destruction of the device, which will require repair at the hardware level (memory resoldering or use of a programmer).
After successful recovery, it is recommended to reset the settings to factory settings (Wipe Data/Factory Reset) to avoid conflicts between the restored system files and the remnants of the old settings. This will ensure stable operation of the system.
Why may recovery fail?
A common reason for failure is a mismatch between Android versions. You cannot restore a backup from Android 13 to a device currently running Android 11 without first flashing the appropriate version of the kernel and system libraries. The partition structure may differ.
Common errors and ways to prevent them
One of the most common mistakes is trying to restore a backup made on another device. Even if the phone models are the same, but have different revisions of motherboards or modem versions, restoration can lead to unstable operation of the connection or touch screen.
Another problem is damage to the backup file during the recording process. If you are using an old or cheap memory card, the write speed may be too slow, resulting in timeouts and bad sectors in the image file. Always check the integrity of the file by comparing checksums (MD5 or SHA1), if this option is provided by the tool.
Also, users often forget about data encryption. On modern Android devices, the Data section is encrypted. When restoring to a clean system or after a reset, the encryption keys may not work and the data will remain inaccessible. In such cases, formatting the encryption partition before restoring helps, but this will delete old data, so the method is applicable only with a full system backup.
The regularity of creating copies is the key to security. Don't make a backup once when you buy a phone. Update the backup before each major intervention in the system: installing a custom kernel, changing system files, or updating the Android version.
Keep backups on different media. Rule 3-2-1 says: three copies of data, on two different types of media, one of which is located in another location (for example, the cloud).
Is it possible to make a backup without root access?
Yes, partially. Using the command adb backup you can save application data and some system settings. However, a full sector-by-sector dump of partitions (Nandroid), necessary to fully restore the system after a failure, requires superuser rights or an unlocked bootloader to install a custom recovery.
How much space does a full copy of the firmware take up?
The volume depends on the fullness of the internal memory and the number of partitions. Typically a full backup takes from 4 to 8 GB. If you choose the compression option in TWRP, the size may be reduced by 30-50%, but the creation process will take longer.
What to do if the phone does not turn on after recovery?
Try going into recovery and resetting the cache (Wipe Cache/Dalvik). If this does not help, the backup may be damaged or incompatible with the current version of the bootloader. In the worst case, you will need to flash the stock firmware through your computer to restore functionality.
Is it safe to store a backup in the cloud?
Storing it in the cloud is safe in terms of file security, but make sure the file is archived and password protected if it contains sensitive personal data. Also consider the size of your cloud storage, as the files can be large.
Do you need to make a backup before updating over the air (OTA)?
It is desirable, but not required for regular updates. OTA updates are usually safe. However, it’s worth making a backup if you have important data that cannot be lost in case of a rare update failure, or if the device already has a modified system.