Android 启动过程汇总

核心提示：Options are modifiers to services. They affect how and when init runs the service.TriggersTriggers are strings which can be used to match certain kinds of event

Options are modifiers to services. They affect how and when init runs the service.

Triggers

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Triggers are strings which can be used to match certain kinds of events and used to cause an action to occur.

The builtin supported commands are defined in device/system/init/keywords.h. Commands are implementd in device/system/init/bultins.c.

The init program only executes five kinds of triggers: “early-init”, “init”, “early-boot”, “boot”, “property:*”. Take a look at the following line in default init.rc.

class_start default

This line is a command for the action corresponding to “boot” trigger. It will start all services whose class name equals to “default”. By default, if no class option is defined for a service, the service’s class name is “default”. So this line will start all the services in the order of position in the file by default. (BTW, you can start any service using start commands, if you like.) Any service is run as a forked process of init, take a look at the source code of service_start in device/system/init.c.

So according to the default init.rc, the following services will be executed step by step:

console: star a shell. The source is in device/system/bin/ash.

adbd: start adb daemon. The source is in device/tools/adbd. By default is disabled.

servicemanager: start binder system. The source is in device/commands/binder.

mountd: mount all fs defined in /system/etc/mountd.conf if started, receive commands through local socket to mount any fs. The source is in device/system/bin/mountd.

debuggerd: start debug system. The source is in device/system/bin/debuggerd.

rild: start radio interface layer daemon. The source is in device/commands/rind.

zygote: start Android Java Runtime and start system server. It’s the most