Android Internals.pdf

Okay, here's a summary of "Android Internals, Volume I" along with a breakdown of the key takeaways, structured to be helpful and engaging:

Android Internals, Volume I: A Quick Dive

This book by Jonathan Levin is your guide to understanding the inner workings of the Android OS, focusing on the perspective of a power user. It's like getting a peek behind the curtain to see how Android really ticks!

What you'll get from it:

• A solid understanding of Android's architecture.
• Skills to troubleshoot and customize your device.
• An appreciation for the complexity and elegance of the Android OS.
• Confidence to dive deeper into Android development or security.

Core Content

Here are some of the core concepts and areas explored in the book:

1. Android's Architectural Evolution:

   • Each version (Cupcake to Lollipop & beyond, with M updates) introduces improvements and features, impacting performance, security, and functionality.
   • Gingerbread brought concurrent garbage collection (better app response) & NFC support. Honeycomb added multi-core support & storage encryption. KitKat aimed at broader device compatibility. Lollipop brought ART.
   • M promises runtime permission enforcement, extended data encryption, and Doze mode for better battery life. *The book shows ways to determine device details, even on customized builds, using terminal commands, and demonstrates how to use /proc to read such properties

2. Android vs. Linux:

   • Android builds upon Linux, but customizes it extensively.
   • Android provides a complete software stack (kernel, GUI, frameworks) simplifying app development
   • Android has its own runtime (Dalvik, ART) and hardware abstraction layer (HAL).

3. Partitions and File Systems:

   • Android devices are partitioned in a certain way, like the scheme partitions used by vendors, including Google.
   • Explains the reasons for the need for separate partitions, such as boot, system, data, cache, vendor, recovery...
   • File systems (Ext4, F2FS) structure these partitions and are critical for data management.
   • Protected filesystems (OBB, ASEC) provide added security (but have limitations on rooted devices).
   • The book shows how to explore device partitions, which can be found in /proc/partitions.
   • Details are given as to various Linux "pseudo-filesystems": /proc, /sys, and others.

4. Boot, Backup, and Recovery:

   • The book also describes the Android boot images (kernel, RAM disk, system partition).
   • The book shows how to boot the devices on a known "safe" copy of the operating system.
   • Details to backup / restore process, including tips for customizing images.

5. /init Process:

   • /init is the first process to start. It starts the system in user mode, like a UN*X system.
   • The book includes deep dives into /init.rc files and USB communication.

6. Daemons (Native Services):

   • The book gives detailed reference to the functions of daemons.
   • Discusses essential daemons like adbd, servicemanager, healthd, vold, surfaceflinger, etc. *Adetailed explanation for each of them

7. Framework Service Architecture:

   • A gentle introduction to the framework service architecture is given.
   • Explains the roles of the TFSWJDFNBOBHFS and TZTFN@TFSWFS processes.

8. Android Through a Linux Lens:

   • The book explains the Android system processes and apps through the /proc filesystem and Linux tools.
   • Covers /proc symlinks, virtual memory management, memory statistics, and tracing system calls.

9. Security:

   • Linux permissions, capabilities, and SELinux are reviewed.
   • Discusses Dalvik-level permissions, code signing, and user-level security (lock screen, multi-user support).
   • Details root methods and device boot.

Q&A

• Q: This book is for "power users." Does that mean I need to be a super-advanced Android hacker to understand it?

  • A: Not at all! The book explains everything clearly, but it does assume you're interested in going deeper than just using apps.

• Q: Can I really customize my Android after reading this book?

  • A: The book provides the knowledge and tools for customization, such as, unpacking boot images, but actual customization may depend on your device's limitations (locked bootloader, etc.).

• Q: Is this book still relevant with newer versions of Android coming out all the time?

  • A: The book is written to be as updated as possible, focusing on core concepts that stay consistent across versions. Also check the companion website NewAndroidBook.com for updates.

• Q: What's the deal with the "Volume I" in the title? What's coming in Volume II?

  • A: Volume I focuses on the power user's perspective. Volume II (coming soon!) dives into the programmer's view, looking at the structure of Android's frameworks.