Android Booting

The bootup of an Android system consists of several phases, which are outlined here.

Device-specific startup

• firmware/bootloader
  • On the ADP1, there are multiple versions of the bootloader

• kernel
• mount root file system

Generic startup

• run /init
  • process /init.rc

See the [Android init language reference]

Sequence of boot steps on ADP1

firmware

• first-stage bootloader runs
  • it detects if a special key is held, and can launch the recovery image, or the 'fastboot' bootloader

kernel

• kernel is loaded
• kernel boots
  • core kernel initialization
  • driver initialization

user space

• user space starts
  • kernel runs /init
    • /init processes /init.rc and /init.rc.<machine_name>
    • activity manager is run
    • dalvik VM is started (zygote)
• activity manager starts core applications
  • com.android.phone - phone application
  • android.process.acore - home (desktop) and a few core apps.
• other processes started by /init:
  • adb
  • mediaserver
  • dbus-daemon
  • akmd

Tools for analyzing Android Bootup

• Bootchart - see Using Bootchart on Android

Notes on the Android startup procedure

Overview

See "Android Initialization Process" at: http://blog.chinaunix.net/u2/85805/showart_1421736.html

strace

http://benno.id.au/blog/2007/11/18/android-runtime-strace

Interaction of different processes on application initialization

Talking about Android Process - http://blog.csdn.net/mawl2002/archive/2009/06/24/4295905.aspx