Introduction to Android Dynamic Partitions and super_partition

The landscape of Android’s storage architecture has evolved significantly, particularly with the introduction of dynamic partitions starting from Android 10. Gone are the days of fixed-size partitions like system, vendor, and product residing in their own distinct physical spaces. Instead, modern Android devices consolidate these into a single, large logical block device known as the super_partition. This change, alongside the adoption of A/B updates and system_as_root, offers greater flexibility for OEMs to manage device storage and facilitate seamless updates. However, it also introduces complexities for users and developers attempting to back up and restore their device partitions.

The super_partition acts as a container, dynamically allocating space to various logical partitions such as system, vendor, product, odm, and system_ext. These logical partitions can be resized, added, or removed during over-the-air (OTA) updates without requiring a full repartitioning of the device. While this improves update efficiency and reduces device footprint, it means that a simple dd command on the entire super_partition block device will yield a sparse image, which is not directly usable for simple restoration, and does not provide an easily accessible backup of individual logical volumes. Understanding these dynamics is crucial for any expert looking to protect their device data effectively.

Prerequisites for a Successful Backup

Essential Tools and Device State

Before embarking on the backup process, ensure you have the following critical components and your device is in the appropriate state:

• Unlocked Bootloader: This is fundamental for flashing custom recoveries or images and gaining necessary access.
• ADB and Fastboot Tools: Ensure you have the latest platform-tools installed on your computer and they are added to your system’s PATH.
• Custom Recovery (e.g., TWRP): While not strictly mandatory for all methods, a custom recovery significantly simplifies the process by providing a robust environment for file system operations and backups. If not available for your specific device, methods requiring root access will be your primary recourse.
• Root Access: For direct on-device partition manipulation, root access via Magisk or similar tools is often required.
• Ample PC Storage: Partition images can be several gigabytes in size. Ensure your computer has sufficient free disk space to store these backups.
• USB Debugging Enabled: On your Android device, navigate to Developer Options and enable USB Debugging.

Method 1: Backing Up Mounted Logical Partitions (Root/Custom Recovery)

This method focuses on extracting individual logical partitions that are typically mounted in Android (or a custom recovery). This approach yields more manageable image files compared to a full super_partition dump.

Step-by-Step: Identifying and Copying Partitions

First, you need to identify the block devices corresponding to your logical partitions. Boot your device into Android (with root) or a custom recovery (like TWRP).

1. Identify Partition Paths:

adb shell ls -l /dev/block/by-name/

This command lists symbolic links to block devices by their partition names (e.g., system, vendor). Note the paths for the partitions you wish to back up (e.g., /dev/block/bootdevice/by-name/system).

2. Check Mounted Status:

adb shell mount

This shows which partitions are currently mounted and their mount points. It’s generally safer to back up partitions that are mounted read-only, or from a custom recovery environment where the OS isn’t actively writing to them.

3. Copy Individual Partition Images:
Once you’ve identified the block device path for a logical partition (e.g., system), you can use the dd command to create an image. It’s highly recommended to save these images to an external SD card or directly stream them to your PC if possible, to avoid filling up internal storage.

• To external storage (if mounted):

  adb shell dd if=/dev/block/by-name/system of=/sdcard/system.img bs=4M status=progress

• To stream directly to your PC (recommended for large partitions):

  adb shell
  
          
          
          
  
              
  
                  
              
              
  
                  
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