The Android Init language contains four main types of statements: actions, commands, services, and options.

All of these are line-oriented and consist of tags separated by Spaces. C-style backslash escapes can be used to insert Spaces into tags. You can also use double quotes to prevent Spaces from splitting text into multiple tags. A backslash can be used for line folding when it is the last character in a line.

Lines starting with # are comments.

Action and Service implicitly declare a new Section. All commands or options belong to the most recently declared Section. Commands or options before the first Section are ignored.

Action and Service have unique names. If the second Action or Service is declared with the same name as an existing Action or Service, it is ignored as an error.

A, the Action

Action is called a sequence of commands. Actions have triggers that determine when the Action should be executed. When an event matching the trigger of an Action occurs, that Action is added to the end of the queue to execute (unless it is already in the queue). Each Action in the queue is enqueued sequentially, and each command in that Action is executed sequentially. The Init process also handles other activities (device creation/destruction, property setting, and process restart) between command execution.

The Action format is as follows:

on <trigger>
   <command>
   <command>
   <command>
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Second, the Service

service <name> <pathname> [ <argument> ]*
   <option>
   <option>
   ...
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Third, the Option

Options are modifiers for the service. They affect how and when Init runs the service.

3.1 critical

3.2 disabled

The service does not automatically start with its classes. Must be started explicitly by name.

3.3 the setenv < name > < value >

3.4 Socket <name> <type> <perm> [<user> [<group> [<seclabel>]]]

Create a Unix domain socket named /dev/socket/<name> and pass its FD to the boot process.

<type> must be “dgram”, “stream”, and “seqpacket”.

The default user and group values are 0.

“Seclabel” is the SELinux security context for a socket. It defaults to a service security context such as secLabel or computations based on a service executable security context.

3.5 the user < username >

3.6 Group <groupname> [<groupname>]*

Before performing this service, switch the group to < groupName >. Group names other than the first group (required) are used to set supplementary groups for the process (via setGroups ()).

The current default is root.

3.7 seclabel < seclabel >

3.8 oneshot

Do not restart the service when you exit it.

3.9 class < name >

3.10 onrestart

This command is executed when the service restarts.

3.11 writepid < file… >

Fourth, the Trigger

A trigger is a string that can be used to match certain types of events and to cause an action to occur.

4.1 the boot

4.2 < name > = < value >

This form of trigger occurs when the attribute <name> is set to a specific value <value>.

You can also test multiple properties to execute a set of commands. Such as:

on property:test.a=1 && property:test.b=1
    setprop test.c 1
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The above fragment sets test.c to 1 only if test.a = 1 and test.b = 1.

Fifth, the Command

5.1 bootchart_init

If configured, start the boot diagram. This is included in the default init.rc.

5.2 chmod < octal mode – > < path >

5.3 chown <owner> <group> <path>

Change the file owner and group.

5.4 class_start < serviceclass >

5.5 class_stop < serviceclass >

If currently running, stops and disables all services for the specified class.

5.6 class_reset < serviceclass >

5.7 copy < SRC > < DST >

Copy files. Similar to writing, but useful for binary/large amounts of data.

5.8 domainname < name >

5.9 enable < servicename >

Turn a disabled service into an enabled service as if the service were not specified to be disabled.

If the service is assumed to be running, it starts immediately.

Typically used when the boot loader sets a variable indicating that a particular service should be started when needed. Such as:

on property:ro.boot.myfancyhardware=1
    enable my_fancy_service_for_my_fancy_hardware
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5.10 exec [< secLabel > [<user> [<group>]*]] — <command> [<argument>]*

5.11 the export < name > < value >

Set the environment variable <name> to equal <value> in the global environment (to be inherited by all processes started after executing this command).

5.12 the hostname < name >

5.13 ifup < interface >

Bring the network interface <interface> online.

5.14 the import < filename >

5.15 insmod < path >

Install the module at <path>.

5.16 load_all_props

5.17 load_persist_props

After decrypting /data, the persistent properties are loaded. This is included in the default init.rc.

5.18 loglevel < level >

5.19 mkdir <path> [mode] [owner] [group]

Create a directory in <path>, optionally using the given schema, owner, and group. If no, use permission 755 to create a directory that is owned by user root and root group. If the directory already exists, the schema, owner, and group are updated.

5.20 mount_all < fstab >

5.21 Mount <type> <device> <dir> [< flag>]* [<options>]

Try to mount the named device in the directory <dir>

<device> specifies the MTD block device name in the form mtd@name.

<flag> Includes ro, RW, remount, noatime…

<options> Includes barrier=1, noauto_da_alloc, discard… Comma-separated strings, for example: barrier=1,noauto_da_alloc

5.22 powerctl

5.23 restart < service >

Like stop, but can’t help service.

5.24 restorecon <path> [<path>]*

5.25 restorecon_recursive <path> []*

Recurse the directory tree named <path> to the security context specified in the File_Contexts configuration.

5.26 the rm < path >

5.27 rmdir < path >

Call RMdir (2) on the given path.

5.28 setprop < name > < value >

5.29 setrLimit <resource> <cur> < Max >

Sets the Rlimit for a resource.

5.23 start < service >

5.24 stop < service >

If the service is currently running, stop it.

5.25 swapon_all < fstab >

5.26 symlink < target > < path >

Create a symbolic link at <path> with a value of <target>

5.27 sysclktz < mins_west_of_gmt >

5.28 the trigger < event >

Trigger event. Use to queue an Action within another Action.

5.29 verity_load_state

5.30 verity_update_state < mount_point >

Internal implementation details for updating dM-Verity status and setting partitions. Since fs_Mgr itself cannot set them directly, the <mount_point>.verified attribute used by ADB is re-installed.

5.31 Wait <path> [<timeout>]

5.32 write < path > < content >

Open the file in, and write a string to it using write(2). If the file does not exist, it will be created. If it does exist, it will be truncated.

Six, the init. Zygote32. Rc

service zygote /system/bin/app_process -Xzygote /system/bin --zygote --start-system-server
    class main
    socket zygote stream 660 root system
    onrestart write /sys/android_power/request_state wake
    onrestart write /sys/power/state on
    onrestart restart media
    onrestart restart netd
    writepid /dev/cpuset/foreground/tasks
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