Android startup analysis-init process & init. rc

Init. rc parsing and chmod changing file attributes are useless.

From: http://h1372865100.blog.163.com/blog/static/2104291032012929114132327/

The init. rc Syntax of android is unique. It can be said that it is a language.

The init. rc syntax is dividedActions, commands, services, and options(Options).

Category	Name	Description
Section	On	Trigger Condition
Same as above ..	Service	Resolution Service
Command	Chdir	Change current working directory
Same as above ..	Chroot	Change the reference root directory location
..	Class_start	Start a service with the class name set
..	Class_stop	Stop a service with the class name set
..	Domainname	Domain Name
..	Exec	Call the program and transfer the process
..	Export	Submit variable
..	Hostname	Host Name
..	Ifup	Activate Nic
..	Insmod	Mount Module
..	Import	Introduce configuration, such as some rc files under etc, which is similar to the import in java
..	Mkdir	Create directory
..	Mount	Mount a File System
..	Setkey	From the source code, it should be the keyword abbreviation for setting a command. For example, you can map domainname to dn.
..	Setprop	Set an attribute
..	Setrlimit	Set the maximum number of files that can be opened by the current program to the maximum number of files that can be opened by the system.
..	Start	Start the service
..	Stop	Stop Service
..	Trigger	Is it a Custom trigger?
..	Symlink	Create a symbolic link
..	Sysclktz	Set Reference time
..	Wait	Waiting for the file to be ready? In Linux, this is a process scheduling function.
..	Write	Write something to a file or device. It must not be the wirte that transmits the message.
..	Copy	Not explained
..	Chown	Change owner
..	Chmod	Change permissions
..	Loglevel	Log output level. If the Log output level is lower than this level
..	Restart	Restart service
Option	Capability	Capability, that is, the system controls the permissions of processes.
Same as above ..	Class	Set Class Name
..	Console	Enable Console
..	Critical	Is it critical, that is, restart more than 4 times within 4 minutes, and then enter the recovery mode
..	Disabled	Not automatically started with Class
..	Group	Group owner
..	Keycodes	I don't understand .....
..	Oneshot	Start only once. Do not restart after unexpected exit
..	Onrestart	Restart
..	Setenv	Add environment variable
..	Socket	Apply for socket Resources
..	User	User attribution
..	Ioprio	Io scheduling priority

(Many Attributes and command usage are different from those of the same name in Linux.)

Init parses init. rc By section. You can view the keyword definition in keywords. h. What mark does init use to parse init. rc in segments? Combined with the content of init. rc, we can see that the segment tag is marked by on and service. The following is a detailed description.

What should I do?

On is an action.

OnEarly-init

Run the command before init and after loading all rc files. In the miui rom, init. rc executes start ueventd in early-init according to keywords. h. start is a COMMAND ).

Here, by the way, ueventd, the underlying (usually the driver) in android notifies the upper-layer events, using uevent. the java layer is implemented through the observer mode and the class used isUeventobserver, UseIntentThe native layer usesAndroid_ OS _ueventobserver.cpp, UseUevent. cPassSocketTransfer. Of course, this is the framework and the following layers, which are not frequently used in development. What's more, these classes are not exposed.

OnInit

Run the command before loading the properties files of propety. It is in the init stage before init is changed to propety service.

OnEarly-boot

After the Attribute service is started, it is executed.

OnBoot

Run the command during boot.

OnProperty: XXXXX = x

This parameter is executed when an attribute is set to an expected value.

 

For init. rc, we can see a lot in combination with the/src/system/core/init/* source code and the init. rc file.

 

==========

Sometimes you need to add your own files to the root, and then find it useless to modify the file attributes in init. rc. I also spent a long time, and I saw a post on the Internet:

Create a script somewhere, for example,/system/bin/mymod. rc
#! /System/bin/sh
Chmod 0777/dev/mynode

Add the following in/init. RC:
Service mymod/system/bin/mymod. RC
Oneshot

(Note that the location/system/bin/is the system directory for generating the file system, not the system directory under the root account)