Android init

http://cecs.wright.edu/~pmateti/Courses/4440/Lectures/Internals/

Android Internals

Table of Contents

• 1. Android-Internals-1: First Glimpse
• 2. Android-Internals-2: Second Look
  • 2.1. Overview
  • 2.2. Android's Init
• 3. Android-Internals-3: Third Look
• 4. Build a ROM
• 5. References
• 6. End

1 Android-Internals-1: First Glimpse

1. Android System
2. Virtual Machines: Dalvik + ART
3. Libraries
4. Background: What is a Program? Process?
5. Selected Processes
6. File System: ext4, etc.
7. Standard Linux Commands within Android
8. Inter Process Communication (IPC)

2 Android-Internals-2: Second Look

2.1 Overview

1. Android Partitions
2. Boot Sequence/ Shutdown Sequence
3. Android Init (Android Framework)
4. Binder (Android Framework) Interprocess/ Component Communication
5. Zygote (Android Framework) The Mother of All Apps
6. System Tools: adb, installd, …
7. Misc Managers: sm - Service, am - activity, pm - package
8. Framework

2.2 Android's Init

1. Android's First Process
2. Action commands.
3. Service declarations.
4. Main init.rc
5. ueventd
6. Boot Logo
7. Android's Init

3 Android-Internals-3: Third Look

1. anon-shared-memory
2. alarm
3. wakelocks-etc
4. low-memory-killer
5. fastboot
6. zipalign
7. deodex
8. Rooting

4 Build a ROM

1. AOSP, CyanogenMod, …
2. ../Build-ROM

5 References

1. Karim Yaghmour, "Embedded Android", O'Reilly Media, Inc., 2013, 412 pp; WSU Safari Books Online 9781449327958
2. Nikolay Elenkov, "An In-Depth Guide to Android's Security Architecture", https://www.nostarch.com/androidsecurity, October 2014, 432 pp. ISBN: 978-1-59327-581-5
3. Jonathan Levin, Android Internals: A Confectioner's Cookbook, Volume I: The Power User's View, http://newandroidbook.com/AIvI-M-RL1.pdf, 267 pp, 2015.
4. Prabhaker Mateti, Lecture Notes on Android Internals and Security, http://www.cs.wright.edu/~pmateti/Courses/4440/Top/

6 End

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Copyright © 2016 www.wright.edu/~pmateti • 2017-08-27

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http://cecs.wright.edu/~pmateti/Courses/4440/Lectures/Internals/Init/init.html

Table of Contents

• 1. Linux Init
• 2. Android Init
• 3. References

1 Linux Init

1. Linux OS kernel invokes the first program (named init) and hence first process (pid == 1)
2. /sbin/init standard location
3. In the Linux/Unix world, there are many designs + implementations that can be used as "init"
   1. A few famous ones: System V, upstart, systemd.
   2. /sbin/init -> /lib/systemd/systemd

   3. % file /lib/systemd/systemd

      /lib/systemd/systemd: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV),
      dynamically linked (uses shared libs), for GNU/Linux 2.6.32, 
      BuildID[sha1]=635141ec29ae1dec6bbb11b117a1a5dad5e0e9cb, 
      stripped
      

4. All inits are driven by their configuration files.

1.1 Expectations of "init"

1. Services or Daemons: Processes that should start early and until system shutdown.
2. Start the services. Watch over them. Should they die/crash, restart.
3. Dependencies: Start the services in a certain order

2 Android Init

1. Configuration Files
2. Property-based triggers
3. Action commands.
4. Service definitions
5. Main init.rc
6. ueventd

1. Android's Init excerpts from Embedded Linux, Chapter 6, PDF

2.1 Service Definition

1. Example: Boot Animation

service bootanim /system/bin/bootanimation
    user graphics
    group graphics
    disabled
    oneshot 

1. https://github.com/android/platform_system_core/blob/master/init/readme.txt Android Init Language, 201x. Describes the language.

3 References

1. Karim Yaghmour, "Embedded Android", O'Reilly Media, Inc., 2013, 412 pp; WSU Safari Books Online 9781449327958; Android Init PDF excerpts, Chapter 6. Required Reading.
2. Karim Yaghmour, Embedded Android Workshop with Nougat, AnDevCon San Francisco 2016, PDF, 175 slides.

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Copyright © 2015 pmateti@wright.edu • www.wright.edu/~pmateti 205-08-30