Easily Extract Lollipop Dat Files
With each iteration of Android, our favorite mobile OS expands and ROM sizes progressively increase. This is in addition to the bloatware added by OEMs that often increases the size of ROMs to a gigabyte or more. Downloading a firmware of that size is problematic, especially in countries with limited data speeds or caps. To make life easier for end users, Google decided to use the compressible EXT4 file system, which replaced the extracted partitions. While it proved beneficial in various regards, there are some potential downsides for certain users.
Before Android 5.0, custom ROMs like OmniROM and AOKP were released as ZIP archives. They were easy to modify, and everyone interested in ROM modding could add an app, bootanimation, or pretty much anything without too much work. Lollipop is much harder to mod because the developer needs to flash the ROM and make a NAND backup to get an img file, or use an external tool like sdat2img. Linux users can extract DAT files easily with the sdat2img tool created by Chinese developer howellzhu. This binary allows users to extract a DAT file to an EXT4 image, which is then easily mountable or extractable.
XDA Recognized Contributor xpirt wrote a guide explaining the decompression process of Lollipop ROMs in detail. The guide contains useful information about using the sdat2img tool and explains the technical jargon used by Google in the relevant source file. Hopefully this guide will help developers to extract ROMs more easily and therefore create modified versions of the firmware that you are currently using.
To read this useful piece of information, please head over to the [HOW TO] Decompress Lollipop .dat files forum thread for the relevant bits.