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The Android Open Source Project4f6e8d72008-10-21 07:00:00 -07001
2Android Init Language
3---------------------
4
5The Android Init Language consists of four broad classes of statements,
6which are Actions, Commands, Services, and Options.
7
8All of these are line-oriented, consisting of tokens separated by
9whitespace. The c-style backslash escapes may be used to insert
10whitespace into a token. Double quotes may also be used to prevent
11whitespace from breaking text into multiple tokens. The backslash,
12when it is the last character on a line, may be used for line-folding.
13
14Lines which start with a # (leading whitespace allowed) are comments.
15
16Actions and Services implicitly declare a new section. All commands
17or options belong to the section most recently declared. Commands
18or options before the first section are ignored.
19
20Actions and Services have unique names. If a second Action or Service
21is declared with the same name as an existing one, it is ignored as
22an error. (??? should we override instead)
23
24
25Actions
26-------
27Actions are named sequences of commands. Actions have a trigger which
28is used to determine when the action should occur. When an event
29occurs which matches an action's trigger, that action is added to
30the tail of a to-be-executed queue (unless it is already on the
31queue).
32
33Each action in the queue is dequeued in sequence and each command in
34that action is executed in sequence. Init handles other activities
35(device creation/destruction, property setting, process restarting)
36"between" the execution of the commands in activities.
37
38Actions take the form of:
39
40on <trigger>
41 <command>
42 <command>
43 <command>
44
45
46Services
47--------
48Services are programs which init launches and (optionally) restarts
49when they exit. Services take the form of:
50
51service <name> <pathname> [ <argument> ]*
52 <option>
53 <option>
54 ...
55
56
57Options
58-------
59Options are modifiers to services. They affect how and when init
60runs the service.
61
62critical
63 This is a device-critical service. If it exits more than four times in
64 four minutes, the device will reboot into recovery mode.
65
66disabled
67 This service will not automatically start with its class.
68 It must be explicitly started by name.
69
70setenv <name> <value>
71 Set the environment variable <name> to <value> in the launched process.
72
73socket <name> <type> <perm> [ <user> [ <group> ] ]
74 Create a unix domain socket named /dev/socket/<name> and pass
Mike Lockwood912ff852010-10-01 08:20:36 -040075 its fd to the launched process. <type> must be "dgram", "stream" or "seqpacket".
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -070076 User and group default to 0.
77
78user <username>
79 Change to username before exec'ing this service.
80 Currently defaults to root. (??? probably should default to nobody)
81 Currently, if your process requires linux capabilities then you cannot use
82 this command. You must instead request the capabilities in-process while
83 still root, and then drop to your desired uid.
84
85group <groupname> [ <groupname> ]*
86 Change to groupname before exec'ing this service. Additional
87 groupnames beyond the (required) first one are used to set the
88 supplemental groups of the process (via setgroups()).
89 Currently defaults to root. (??? probably should default to nobody)
90
Stephen Smalley3fb61102012-11-02 15:22:34 -040091seclabel <securitycontext>
92 Change to securitycontext before exec'ing this service.
93 Primarily for use by services run from the rootfs, e.g. ueventd, adbd.
94 Services on the system partition can instead use policy-defined transitions
95 based on their file security context.
96 If not specified and no transition is defined in policy, defaults to the init context.
97
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -070098oneshot
99 Do not restart the service when it exits.
100
101class <name>
102 Specify a class name for the service. All services in a
103 named class may be started or stopped together. A service
104 is in the class "default" if one is not specified via the
105 class option.
106
107onrestart
108 Execute a Command (see below) when service restarts.
109
110Triggers
111--------
112 Triggers are strings which can be used to match certain kinds
113 of events and used to cause an action to occur.
114
115boot
116 This is the first trigger that will occur when init starts
117 (after /init.conf is loaded)
118
119<name>=<value>
120 Triggers of this form occur when the property <name> is set
121 to the specific value <value>.
122
123device-added-<path>
124device-removed-<path>
125 Triggers of these forms occur when a device node is added
126 or removed.
127
128service-exited-<name>
129 Triggers of this form occur when the specified service exits.
130
131
132Commands
133--------
134
135exec <path> [ <argument> ]*
136 Fork and execute a program (<path>). This will block until
137 the program completes execution. It is best to avoid exec
138 as unlike the builtin commands, it runs the risk of getting
139 init "stuck". (??? maybe there should be a timeout?)
140
141export <name> <value>
142 Set the environment variable <name> equal to <value> in the
143 global environment (which will be inherited by all processes
144 started after this command is executed)
145
146ifup <interface>
147 Bring the network interface <interface> online.
148
149import <filename>
150 Parse an init config file, extending the current configuration.
151
152hostname <name>
153 Set the host name.
154
Jay Freeman (saurik)e7cb1372008-11-17 06:41:10 +0000155chdir <directory>
156 Change working directory.
157
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700158chmod <octal-mode> <path>
159 Change file access permissions.
160
161chown <owner> <group> <path>
162 Change file owner and group.
163
Jay Freeman (saurik)e7cb1372008-11-17 06:41:10 +0000164chroot <directory>
165 Change process root directory.
166
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700167class_start <serviceclass>
168 Start all services of the specified class if they are
169 not already running.
170
171class_stop <serviceclass>
172 Stop all services of the specified class if they are
173 currently running.
174
175domainname <name>
176 Set the domain name.
177
178insmod <path>
179 Install the module at <path>
180
181mkdir <path> [mode] [owner] [group]
182 Create a directory at <path>, optionally with the given mode, owner, and
183 group. If not provided, the directory is created with permissions 755 and
184 owned by the root user and root group.
185
186mount <type> <device> <dir> [ <mountoption> ]*
187 Attempt to mount the named device at the directory <dir>
188 <device> may be of the form mtd@name to specify a mtd block
189 device by name.
190 <mountoption>s include "ro", "rw", "remount", "noatime", ...
191
Stephen Smalley3fb61102012-11-02 15:22:34 -0400192restorecon <path>
193 Restore the file named by <path> to the security context specified
194 in the file_contexts configuration.
195 Not required for directories created by the init.rc as these are
196 automatically labeled correctly by init.
197
198setcon <securitycontext>
199 Set the current process security context to the specified string.
200 This is typically only used from early-init to set the init context
201 before any other process is started.
202
203setenforce 0|1
204 Set the SELinux system-wide enforcing status.
205 0 is permissive (i.e. log but do not deny), 1 is enforcing.
206
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700207setkey
208 TBD
209
210setprop <name> <value>
211 Set system property <name> to <value>.
212
213setrlimit <resource> <cur> <max>
214 Set the rlimit for a resource.
215
Stephen Smalley0e23fee2012-11-28 13:52:12 -0500216setsebool <name> <value>
Stephen Smalley3fb61102012-11-02 15:22:34 -0400217 Set SELinux boolean <name> to <value>.
218 <value> may be 1|true|on or 0|false|off
219
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700220start <service>
221 Start a service running if it is not already running.
222
223stop <service>
224 Stop a service from running if it is currently running.
225
226symlink <target> <path>
227 Create a symbolic link at <path> with the value <target>
228
The Android Open Source Project35237d12008-12-17 18:08:08 -0800229sysclktz <mins_west_of_gmt>
230 Set the system clock base (0 if system clock ticks in GMT)
231
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700232trigger <event>
233 Trigger an event. Used to queue an action from another
234 action.
235
Patrick McCormick96d0a4d2011-02-04 10:51:39 -0800236wait <path> [ <timeout> ]
237 Poll for the existence of the given file and return when found,
238 or the timeout has been reached. If timeout is not specified it
239 currently defaults to five seconds.
240
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700241write <path> <string> [ <string> ]*
242 Open the file at <path> and write one or more strings
243 to it with write(2)
244
245
246Properties
247----------
248Init updates some system properties to provide some insight into
249what it's doing:
250
251init.action
252 Equal to the name of the action currently being executed or "" if none
253
254init.command
255 Equal to the command being executed or "" if none.
256
257init.svc.<name>
258 State of a named service ("stopped", "running", "restarting")
259
260
261Example init.conf
262-----------------
263
264# not complete -- just providing some examples of usage
265#
266on boot
267 export PATH /sbin:/system/sbin:/system/bin
268 export LD_LIBRARY_PATH /system/lib
269
270 mkdir /dev
271 mkdir /proc
272 mkdir /sys
273
274 mount tmpfs tmpfs /dev
275 mkdir /dev/pts
276 mkdir /dev/socket
277 mount devpts devpts /dev/pts
278 mount proc proc /proc
279 mount sysfs sysfs /sys
280
281 write /proc/cpu/alignment 4
282
283 ifup lo
284
285 hostname localhost
286 domainname localhost
287
288 mount yaffs2 mtd@system /system
289 mount yaffs2 mtd@userdata /data
290
291 import /system/etc/init.conf
292
293 class_start default
294
295service adbd /sbin/adbd
296 user adb
297 group adb
298
299service usbd /system/bin/usbd -r
300 user usbd
301 group usbd
302 socket usbd 666
303
304service zygote /system/bin/app_process -Xzygote /system/bin --zygote
305 socket zygote 666
306
307service runtime /system/bin/runtime
308 user system
309 group system
310
311on device-added-/dev/compass
312 start akmd
313
314on device-removed-/dev/compass
315 stop akmd
316
317service akmd /sbin/akmd
318 disabled
319 user akmd
320 group akmd
321
322Debugging notes
323---------------
324By default, programs executed by init will drop stdout and stderr into
325/dev/null. To help with debugging, you can execute your program via the
326Andoird program logwrapper. This will redirect stdout/stderr into the
327Android logging system (accessed via logcat).
328
329For example
330service akmd /system/bin/logwrapper /sbin/akmd