Introduction: Navigating Dynamic Partitions in LineageOS Ports

Porting custom ROMs like LineageOS to Android devices is a challenging yet rewarding endeavor. A particularly complex hurdle arises when dealing with devices featuring non-standard dynamic partition configurations. While Android’s dynamic partition system (introduced in Android 10) aims to simplify A/B updates and improve storage efficiency, deviations from the standard implementation can lead to significant build and flashing issues for custom ROM developers. This expert-level guide delves into the intricacies of dynamic partitions, helps identify non-standard layouts, and provides practical strategies for successfully porting LineageOS to such devices, focusing on resizing and managing these critical storage components.

The Android Dynamic Partition Landscape

What are Dynamic Partitions?

Dynamic partitions are a core component of Android’s Project Treble initiative, designed to enable seamless A/B updates and flexible partition management. Instead of fixed, physical partitions for components like system, vendor, and product, dynamic partitions reside as logical volumes within a single, large physical partition called super. This allows the Android operating system to dynamically resize these logical partitions during over-the-air (OTA) updates, reducing the overall system image size and facilitating more efficient updates.

Decoding the `super` Partition Structure

The super partition holds metadata that describes the layout and sizes of all logical partitions within it. These logical partitions (e.g., system_a, system_b, vendor_a, vendor_b) are essentially filesystems allocated space from the common super pool. The device’s fstab and vendor_fstab files instruct the bootloader and kernel how to mount these logical volumes. Tools like dump_super can inspect the metadata:

adb shell dump_super /dev/block/by-name/super

This command outputs detailed information about the partition groups, their sizes, and the logical partitions contained within them, crucial for understanding the device’s stock configuration.

Identifying Non-Standard Dynamic Partition Configurations

Common Deviations from the Norm

A ‘standard’ dynamic partition setup typically involves a super partition of a certain size (often 4-8GB) containing separate slots for A/B partitions like system_a/b, vendor_a/b, etc. Non-standard configurations can manifest in several ways:

• Unusual `super` Partition Size: The physical super partition might be significantly smaller or larger than what LineageOS’s build system expects.
• Non-Standard Grouping: Logical partitions might be grouped differently than the conventional ‘main’ or ‘qti_dynamic_partitions’ structure.
• Missing or Extra Partitions: Devices might omit expected dynamic partitions (e.g., product, system_ext) or include custom OEM dynamic partitions.
• Partial Dynamic Partitions: Some older devices or niche implementations might use dynamic partitions for only a subset of their system, with others remaining physical.

Practical Inspection: Tools and Commands

To accurately assess your device’s configuration, you need to gather information directly from the device:

1. Physical `super` Partition Size:

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

   This will show the symlink to the actual block device. Then, use `blockdev –getsize64` or `fdisk -l` on the corresponding `/dev/block/sdaX` to get the raw size in bytes.

2. Logical Partition Layout: Use dump_super as shown above to see partition names, sizes, and group allocations.
3. Fstab Entries: Inspect /vendor/etc/fstab. and /etc/fstab. (or similar paths in stock ROM). Look for lines containing logical or referencing dynamic partitions, especially the mount options like slotselect.

The Core Challenge: LineageOS and `super` Partition Mismatch

LineageOS builds are based on AOSP, which makes certain assumptions about dynamic partitions. When these assumptions clash with a device’s non-standard configuration, you’ll encounter build errors or, more commonly, boot loops (e.g., device booting to fastbootd instead of system) during flashing. The primary issue is often that the combined size required by LineageOS for its logical partitions (system, vendor, product, system_ext, odm, all in A/B slots) exceeds the capacity of the device’s super partition, or the allocated group sizes are incorrect. This can manifest as:

• `lpmake` errors during build, indicating insufficient space or misconfigured groups.
• `fastboot` errors during flashing, such as
  
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