Introduction to Android Dynamic Partitions and super.img

Modern Android devices, particularly those running Android 10 and newer, have moved away from traditional, fixed partition layouts to a more flexible system known as Dynamic Partitions. This change introduces the super.img, a single physical partition that dynamically houses logical partitions like system, vendor, product, and odm. This architecture provides significant benefits for Over-The-Air (OTA) updates and device manufacturers, allowing for seamless partition resizing and updates without needing to reflash the entire device. However, for enthusiasts and developers working on custom ROMs, kernels, or deeper system modifications, interacting with super.img presents a new challenge: how to unpack, modify, and repack these dynamic partitions effectively.

This expert-level guide will demystify the super.img format, providing a comprehensive, step-by-step tutorial on how to extract its contents, make surgical modifications to individual logical partitions, and then meticulously reconstruct a flashable super.img. Mastering this process is crucial for advanced Android customization, enabling everything from tweaking system properties to integrating custom binaries into read-only partitions.

Understanding the Structure of super.img

At its core, super.img isn’t a simple filesystem image like an ext4 partition. Instead, it’s a container managed by Android’s Logical Partition Manager (LPM). It contains metadata that describes the layout of various logical partitions (e.g., system, vendor, product) and their respective sizes and attributes. These logical partitions themselves are typically standard filesystem images (ext4 or f2fs) embedded within the super.img container. The LPM dynamically allocates space within the super.img for these logical partitions, allowing for flexible resizing during OTA updates.

Key components within super.img:

• Metadata: Describes the partition layout, including partition names, sizes, groups, and attributes.
• Partition Groups: Logical partitions are often organized into groups (e.g., main_group), allowing for collective management of space.
• Logical Partition Images: The actual filesystem images (system.img, vendor.img, etc.) that contain the Android OS components.

Prerequisites and Tools

To successfully navigate the dynamic partition landscape, you’ll need a Linux environment (Ubuntu or Debian is recommended) and a set of specialized tools:

• Android SDK Platform Tools: For adb and fastboot utilities.
• lpunpack and lpmake: Essential tools from the Android Open Source Project (AOSP) for unpacking and repacking super.img. These can often be found pre-compiled or built from AOSP source.
• simg2img and img2simg: Utilities to convert between sparse and raw Android images. Many factory images are sparse.
• Standard Linux Utilities: mount, umount, e2fsck, resize2fs for working with filesystem images.
• payload-dumper-go: (Optional, but highly recommended) A tool for extracting partition images from payload.bin found in many factory images.

Step-by-Step Guide: Unpacking super.img

1. Obtaining super.img

You can acquire the super.img in a few ways:

• From a Factory Image: Most official factory images come as a payload.bin. Use payload-dumper-go to extract all partition images, including super.img.
• From a Rooted Device: If your device is rooted, you can pull the image directly from the device.

# Example 1: Extracting from payload.bin (requires payload-dumper-go)sudo apt install golang-go # If not installedgo install github.com/ssut/payload-dumper-go@latest# Assuming payload.bin is in the current directory~/.go/bin/payload-dumper-go -payload payload.bin# This will output all images, including super.img, in the 'output' directory.

# Example 2: Pulling from a rooted deviceadb shell

        
        
        

            

                
            
            

                
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