android的啟動腳本(init.rc)文件的語法，參考資料：
Android 初始化語言(Android Init Language)
Android初始化腳本語言包含四種類型的語句：
動作(Actions)
指令(Commands)
服務(Services)
選項(Options)
該語言的語法包括下列約定：
所有類型的語句都是基于行(line-oriented)的，
一個語句包含若干個tokens，token之間通過空格字符分隔.
如果一個token中需要包含空格字符，則需要通過C語言風格的反斜線('\')來轉義，或者使用雙引號把整個token引起來。反斜線還可以出現在一行
的末尾，表示下一行的內容仍然屬于當前語句。
以'#'開始的行是注釋行。
動作(Actions)和服務(Services)語句隱含表示一個新的段落
(section)的開始。
所有的指令(commands)和選項(options)歸屬于上方最近的一個段落。在第一個段落之前的指令(commands)和選項
(options)是無效的。
動作(Actions)和服務(Services)擁有唯一性的名字。如果出現重
名，那么后出現的定義將被作為錯誤忽略掉。動作
(Actions)
動作(Actions)是一個有名字的指令(commands)序列。每個動作
(Actions)都定義一個觸發條件(trigger)，用于指示什么時候執行這個動作。當與動作的觸發器匹配的事件發生時，該動作將被添加到一個即將
被執行的隊列的隊尾(除非它已經在隊列中)。
隊列中的每一個動作被依次取出執行，動作中的每一個指令也將依次執行。初始化程序
(Init)在執行一個動作的各項指令的期間，還需要處理其它操作(比如，設備創建/銷毀，屬性設置，進程重啟)。
一個動作定義的形式如下：on
服務(Services)服務是初始化程序需要啟動的一些程序，初始化程序還有可能會在這些程序退出之后重啟它們。
Services take 一個服務定義的形式如下：service [ ]*
...
選項(Options)
選項將影響控制初始化程序運行服務的時機和方法。可能的選項如下表。
選項
說明
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.
觸發器(Triggers)
觸發器是一個字符串，用于匹配特定的事件，這些事件將觸發觸發器所屬動作
(Actions)的執行。
觸發器
說明
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-device-removed-
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).
屬性(Properties)初始化程序(Init)可以根據需要修改一些系統的屬性。
屬性
說明
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
)
)
)
