分类: LINUX
2013-04-01 16:57:20
原文地址:Android 初始化脚本语法解析 作者:amuhong
Android初始化脚本语言包含四种类型的语句:
该语言的语法包括下列约定:
动作(Actions)是一个有名字的指令(commands)序列。每个动作(Actions)都定义一个触发条件(trigger),用于指示 什么时候执行这个动作。当与动作的触发器匹配的事件发生时,该动作将被添加到一个即将被执行的队列的队尾(除非它已经在队列中)。
队列中的
每一个动作被依次取出执行,动作中的每一个指令也将依次执行。初始化程序(Init)在执行一个动作的各项指令的期间,还需要处理其它操作(比如,设备创
建/销毁,属性设置,进程重启)。
一个动作定义的形式如下:
on
服务(Services)
服务是初始化程序需要启动的一些程序,初始化程序还有可能会在这些程序退出之后重启它们。Services take 一个服务定义的形式如下:service[ ]*
选项(Options)
选项将影响控制初始化程序运行服务的时机和方法。可能的选项如下表。
选项 | 说明 |
disabled |
This service will not automatically start with its class. It must be explicitly started by name. |
socket
|
Create a unix domain socket named /dev/socket/
and pass its fd to the launched process. Valid
values include dgram and stream . user
and group default to 0. |
user |
Change to username before exec'ing this service. Currently defaults to root. |
group |
Change to groupname before exec'ing this service. Additional
groupnames beyond the first, which is required, are used to set
additional groups of the process (with setgroups() ).
Currently defaults to root. |
capability [ |
Set linux capability before exec'ing this service |
oneshot |
Do not restart the service when it exits. |
class |
Specify a class name for the service. All services in a named class must start and stop together. A service is considered of class "default" if one is not specified via the class option. |
触发器(Triggers)
触发器是一个字符串,用于匹配特定的事件,这些事件将触发触发器所属动作(Actions)的执行。
触发器 | 说明 |
boot |
This is the first trigger that occurs when init starts (after /init.conf
is loaded). |
|
Triggers of this form occur when the property
is set to the specific value . |
device-added- |
Triggers of these forms occur when a device node is added or removed. |
service-exited- |
Triggers of this form occur when the specified service exits. |
指令(Commands)
Command | Description |
exec |
Fork and execute a program ( ). This
will block until the program completes execution. Try to avoid exec.
Unlike the builtin commands, it runs the risk of getting
init "stuck". |
export |
Set the environment variable equal
to in the global environment (which will be
inherited by all processes started after this command is executed). |
ifup |
Bring the network interface
online. |
import |
Parse an init config file, extending the current configuration. |
hostname |
Set the host name. |
class_start |
Start all services of the specified class if they are not already running. |
class_stop |
Stop all services of the specified class if they are currently running. |
domainname |
Set the domain name. |
insmod |
Install the module at . |
mkdir |
Make a directory at . |
mount |
Attempt to mount the named device at the directory
. This may be of the form mtd@name
to specify a mtd block device by name. |
setkey |
- currenlty undefined - |
setprop |
Set system property to . |
setrlimit |
Set the rlimit for a resource. |
start |
Start a service running if it is not already running. |
stop |
Stop a service from running if it is currently running. |
symlink |
Create a symbolic link at with the
value . |
write |
Open the file at and write one or
more strings to it with write(2). |
属性(Properties)
初始化程序(Init)可以根据需要修改一些系统的属性。属性 | 说明 |
init.action |
Equal to the name of the action currently being executed or "" if none. |
init.command |
Equal to the command being executed or "" if none. |
init.svc. |
State of a named service ("stopped", "running", or "restarting"). |
init.rc文件示例
on boot
export PATH /sbin:/system/sbin:/system/bin
export LD_LIBRARY_PATH /system/lib
mkdir /dev
mkdir /proc
mkdir /sys
mount tmpfs tmpfs /dev
mkdir /dev/pts
mkdir /dev/socket
mount devpts devpts /dev/pts
mount proc proc /proc
mount sysfs sysfs /sys
write /proc/cpu/alignment 4
ifup lo
hostname localhost
domainname localhost
mount yaffs2 mtd@system /system
mount yaffs2 mtd@userdata /data
import /system/etc/init.conf
class_start default
service adbd /sbin/adbd
user adb
group adb
service usbd /system/bin/usbd -r
user usbd
group usbd
socket usbd 666
service zygote /system/bin/app_process -Xzygote /system/bin --zygote
socket zygote 666
service runtime /system/bin/runtime
user system
group system
on device-added-/dev/compass
start akmd
on device-removed-/dev/compass
stop akmd
service akmd /sbin/akmd
disabled
user akmd
group akmd