blob: 4481e24ef3e1a9fb9924d6e8da5c8b9526216d17 [file] [log] [blame]
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -07001
2Android Init Language
3---------------------
4
Tom Cherry3be66ed2015-09-01 14:49:38 -07005The Android Init Language consists of five broad classes of statements,
6which are Actions, Commands, Services, Options, and Imports.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -07007
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
Tom Cherry3be66ed2015-09-01 14:49:38 -070020Actions and Services have unique names. If a second Action is defined
21with the same name as an existing one, its commands are appended to
22the commands of the existing action. If a second Service is defined
23with the same name as an existing one, it is ignored and an error
24message is logged.
25
26
27Init .rc Files
28--------------
29The init language is used in plaintext files that take the .rc file
30extension. These are typically multiple of these in multiple
31locations on the system, described below.
32
33/init.rc is the primary .rc file and is loaded by the init executable
34at the beginning of its execution. It is responsible for the initial
35set up of the system. It imports /init.${ro.hardware}.rc which is the
36primary vendor supplied .rc file.
37
38During the mount_all command, the init executable loads all of the
39files contained within the /{system,vendor,odm}/etc/init/ directories.
40These directories are intended for all Actions and Services used after
41file system mounting.
42
Tom Cherry1fb20b82016-01-20 16:53:08 -080043One may specify paths in the mount_all command line to have it import
44.rc files at the specified paths instead of the default ones listed above.
45This is primarily for supporting factory mode and other non-standard boot
46modes. The three default paths should be used for the normal boot process.
47
Tom Cherry3be66ed2015-09-01 14:49:38 -070048The intention of these directories is as follows
49 1) /system/etc/init/ is for core system items such as
Tom Cherry1fb20b82016-01-20 16:53:08 -080050 SurfaceFlinger, MediaService, and logcatd.
Tom Cherry3be66ed2015-09-01 14:49:38 -070051 2) /vendor/etc/init/ is for SoC vendor items such as actions or
52 daemons needed for core SoC functionality.
53 3) /odm/etc/init/ is for device manufacturer items such as
54 actions or daemons needed for motion sensor or other peripheral
55 functionality.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -070056
Tom Cherry1fb20b82016-01-20 16:53:08 -080057All services whose binaries reside on the system, vendor, or odm
58partitions should have their service entries placed into a
59corresponding init .rc file, located in the /etc/init/
60directory of the partition where they reside. There is a build
61system macro, LOCAL_INIT_RC, that handles this for developers. Each
62init .rc file should additionally contain any actions associated with
63its service.
64
65An example is the logcatd.rc and Android.mk files located in the
66system/core/logcat directory. The LOCAL_INIT_RC macro in the
67Android.mk file places logcatd.rc in /system/etc/init/ during the
68build process. Init loads logcatd.rc during the mount_all command and
69allows the service to be run and the action to be queued when
70appropriate.
71
72This break up of init .rc files according to their daemon is preferred
73to the previously used monolithic init .rc files. This approach
74ensures that the only service entries that init reads and the only
75actions that init performs correspond to services whose binaries are in
76fact present on the file system, which was not the case with the
77monolithic init .rc files. This additionally will aid in merge
78conflict resolution when multiple services are added to the system, as
79each one will go into a separate file.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -070080
81Actions
82-------
83Actions are named sequences of commands. Actions have a trigger which
84is used to determine when the action should occur. When an event
85occurs which matches an action's trigger, that action is added to
86the tail of a to-be-executed queue (unless it is already on the
87queue).
88
89Each action in the queue is dequeued in sequence and each command in
90that action is executed in sequence. Init handles other activities
91(device creation/destruction, property setting, process restarting)
92"between" the execution of the commands in activities.
93
94Actions take the form of:
95
Tom Cherry3be66ed2015-09-01 14:49:38 -070096on <trigger> [&& <trigger>]*
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -070097 <command>
98 <command>
99 <command>
100
101
102Services
103--------
104Services are programs which init launches and (optionally) restarts
105when they exit. Services take the form of:
106
107service <name> <pathname> [ <argument> ]*
108 <option>
109 <option>
110 ...
111
112
113Options
114-------
115Options are modifiers to services. They affect how and when init
116runs the service.
117
118critical
Elliott Hughesd62f0602015-06-12 18:02:20 -0700119 This is a device-critical service. If it exits more than four times in
120 four minutes, the device will reboot into recovery mode.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700121
122disabled
Elliott Hughesd62f0602015-06-12 18:02:20 -0700123 This service will not automatically start with its class.
124 It must be explicitly started by name.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700125
126setenv <name> <value>
Elliott Hughesd62f0602015-06-12 18:02:20 -0700127 Set the environment variable <name> to <value> in the launched process.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700128
Elliott Hughes8d82ea02015-02-06 20:15:18 -0800129socket <name> <type> <perm> [ <user> [ <group> [ <seclabel> ] ] ]
Elliott Hughesd62f0602015-06-12 18:02:20 -0700130 Create a unix domain socket named /dev/socket/<name> and pass
131 its fd to the launched process. <type> must be "dgram", "stream" or "seqpacket".
132 User and group default to 0.
133 'seclabel' is the SELinux security context for the socket.
134 It defaults to the service security context, as specified by seclabel or
135 computed based on the service executable file security context.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700136
137user <username>
Elliott Hughesd62f0602015-06-12 18:02:20 -0700138 Change to username before exec'ing this service.
139 Currently defaults to root. (??? probably should default to nobody)
Tom Cherrydbddb402015-12-11 12:54:50 -0800140 As of Android M, processes should use this option even if they
141 require linux capabilities. Previously, to acquire linux
142 capabilities, a process would need to run as root, request the
143 capabilities, then drop to its desired uid. There is a new
144 mechanism through fs_config that allows device manufacturers to add
145 linux capabilities to specific binaries on a file system that should
146 be used instead. This mechanism is described on
147 http://source.android.com/devices/tech/config/filesystem.html. When
148 using this new mechanism, processes can use the user option to
149 select their desired uid without ever running as root.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700150
151group <groupname> [ <groupname> ]*
Elliott Hughesd62f0602015-06-12 18:02:20 -0700152 Change to groupname before exec'ing this service. Additional
153 groupnames beyond the (required) first one are used to set the
154 supplemental groups of the process (via setgroups()).
155 Currently defaults to root. (??? probably should default to nobody)
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700156
Elliott Hughes8d82ea02015-02-06 20:15:18 -0800157seclabel <seclabel>
158 Change to 'seclabel' before exec'ing this service.
Stephen Smalley3fb61102012-11-02 15:22:34 -0400159 Primarily for use by services run from the rootfs, e.g. ueventd, adbd.
160 Services on the system partition can instead use policy-defined transitions
161 based on their file security context.
162 If not specified and no transition is defined in policy, defaults to the init context.
163
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700164oneshot
Elliott Hughesd62f0602015-06-12 18:02:20 -0700165 Do not restart the service when it exits.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700166
167class <name>
Elliott Hughesd62f0602015-06-12 18:02:20 -0700168 Specify a class name for the service. All services in a
169 named class may be started or stopped together. A service
170 is in the class "default" if one is not specified via the
171 class option.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700172
173onrestart
Elliott Hughesd62f0602015-06-12 18:02:20 -0700174 Execute a Command (see below) when service restarts.
175
176writepid <file...>
177 Write the child's pid to the given files when it forks. Meant for
178 cgroup/cpuset usage.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700179
Elliott Hughes841b2632015-02-12 14:28:54 -0800180
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700181Triggers
182--------
Tom Cherry3be66ed2015-09-01 14:49:38 -0700183Triggers are strings which can be used to match certain kinds of
184events and used to cause an action to occur.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700185
Tom Cherry3be66ed2015-09-01 14:49:38 -0700186Triggers are subdivided into event triggers and property triggers.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700187
Tom Cherry3be66ed2015-09-01 14:49:38 -0700188Event triggers are strings triggered by the 'trigger' command or by
189the QueueEventTrigger() function within the init executable. These
190take the form of a simple string such as 'boot' or 'late-init'.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700191
Tom Cherry3be66ed2015-09-01 14:49:38 -0700192Property triggers are strings triggered when a named property changes
193value to a given new value or when a named property changes value to
194any new value. These take the form of 'property:<name>=<value>' and
195'property:<name>=*' respectively. Property triggers are additionally
196evaluated and triggered accordingly during the initial boot phase of
197init.
Badhri Jagan Sridharan0b415122014-10-10 23:19:06 -0700198
Tom Cherry3be66ed2015-09-01 14:49:38 -0700199An Action can have multiple property triggers but may only have one
200event trigger.
Badhri Jagan Sridharan0b415122014-10-10 23:19:06 -0700201
Tom Cherry3be66ed2015-09-01 14:49:38 -0700202For example:
203'on boot && property:a=b' defines an action that is only executed when
204the 'boot' event trigger happens and the property a equals b.
205
206'on property:a=b && property:c=d' defines an action that is executed
207at three times,
208 1) During initial boot if property a=b and property c=d
209 2) Any time that property a transitions to value b, while property
210 c already equals d.
211 3) Any time that property c transitions to value d, while property
212 a already equals b.
Badhri Jagan Sridharan0b415122014-10-10 23:19:06 -0700213
Elliott Hughes841b2632015-02-12 14:28:54 -0800214
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700215Commands
216--------
217
Elliott Hughes91a3be52015-03-20 11:00:15 -0700218bootchart_init
219 Start bootcharting if configured (see below).
220 This is included in the default init.rc.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700221
222chmod <octal-mode> <path>
223 Change file access permissions.
224
225chown <owner> <group> <path>
226 Change file owner and group.
227
228class_start <serviceclass>
229 Start all services of the specified class if they are
230 not already running.
231
232class_stop <serviceclass>
Elliott Hughes91a3be52015-03-20 11:00:15 -0700233 Stop and disable all services of the specified class if they are
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700234 currently running.
235
Elliott Hughes91a3be52015-03-20 11:00:15 -0700236class_reset <serviceclass>
237 Stop all services of the specified class if they are
238 currently running, without disabling them. They can be restarted
239 later using class_start.
240
241copy <src> <dst>
242 Copies a file. Similar to write, but useful for binary/large
243 amounts of data.
244
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700245domainname <name>
246 Set the domain name.
247
JP Abgrall3beec7e2014-05-02 21:14:29 -0700248enable <servicename>
249 Turns a disabled service into an enabled one as if the service did not
250 specify disabled.
251 If the service is supposed to be running, it will be started now.
252 Typically used when the bootloader sets a variable that indicates a specific
253 service should be started when needed. E.g.
254 on property:ro.boot.myfancyhardware=1
255 enable my_fancy_service_for_my_fancy_hardware
256
Elliott Hughes91a3be52015-03-20 11:00:15 -0700257exec [ <seclabel> [ <user> [ <group> ]* ] ] -- <command> [ <argument> ]*
258 Fork and execute command with the given arguments. The command starts
259 after "--" so that an optional security context, user, and supplementary
260 groups can be provided. No other commands will be run until this one
Mark Salyzyn17fff892015-06-02 11:11:02 -0700261 finishes. <seclabel> can be a - to denote default.
Elliott Hughes91a3be52015-03-20 11:00:15 -0700262
Elliott Hughes91a3be52015-03-20 11:00:15 -0700263export <name> <value>
264 Set the environment variable <name> equal to <value> in the
265 global environment (which will be inherited by all processes
266 started after this command is executed)
267
268hostname <name>
269 Set the host name.
270
271ifup <interface>
272 Bring the network interface <interface> online.
273
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700274insmod <path>
275 Install the module at <path>
276
Elliott Hughes91a3be52015-03-20 11:00:15 -0700277load_all_props
278 Loads properties from /system, /vendor, et cetera.
279 This is included in the default init.rc.
280
281load_persist_props
282 Loads persistent properties when /data has been decrypted.
283 This is included in the default init.rc.
284
Elliott Hughesf682b472015-02-06 12:19:48 -0800285loglevel <level>
286 Sets the kernel log level to level. Properties are expanded within <level>.
287
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700288mkdir <path> [mode] [owner] [group]
289 Create a directory at <path>, optionally with the given mode, owner, and
290 group. If not provided, the directory is created with permissions 755 and
Johan Redestig0b42ba22015-03-15 17:39:41 +0100291 owned by the root user and root group. If provided, the mode, owner and group
292 will be updated if the directory exists already.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700293
Hung-ying Tyandc738ea2016-01-14 11:18:21 +0800294mount_all <fstab> [ <path> ]*
295 Calls fs_mgr_mount_all on the given fs_mgr-format fstab and imports .rc files
296 at the specified paths (e.g., on the partitions just mounted). Refer to the
297 section of "Init .rc Files" for detail.
Elliott Hughes91a3be52015-03-20 11:00:15 -0700298
Niklas Tibblingbc3f69f2012-08-01 13:15:38 +0200299mount <type> <device> <dir> [ <flag> ]* [<options>]
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700300 Attempt to mount the named device at the directory <dir>
301 <device> may be of the form mtd@name to specify a mtd block
302 device by name.
Niklas Tibblingbc3f69f2012-08-01 13:15:38 +0200303 <flag>s include "ro", "rw", "remount", "noatime", ...
304 <options> include "barrier=1", "noauto_da_alloc", "discard", ... as
305 a comma separated string, eg: barrier=1,noauto_da_alloc
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700306
Elliott Hughes91a3be52015-03-20 11:00:15 -0700307powerctl
308 Internal implementation detail used to respond to changes to the
309 "sys.powerctl" system property, used to implement rebooting.
310
311restart <service>
312 Like stop, but doesn't disable the service.
313
Stephen Smalley726e8f72013-10-09 16:02:09 -0400314restorecon <path> [ <path> ]*
Stephen Smalley3fb61102012-11-02 15:22:34 -0400315 Restore the file named by <path> to the security context specified
316 in the file_contexts configuration.
317 Not required for directories created by the init.rc as these are
318 automatically labeled correctly by init.
319
Stephen Smalley726e8f72013-10-09 16:02:09 -0400320restorecon_recursive <path> [ <path> ]*
321 Recursively restore the directory tree named by <path> to the
322 security contexts specified in the file_contexts configuration.
Stephen Smalley726e8f72013-10-09 16:02:09 -0400323
Elliott Hughes91a3be52015-03-20 11:00:15 -0700324rm <path>
325 Calls unlink(2) on the given path. You might want to
326 use "exec -- rm ..." instead (provided the system partition is
327 already mounted).
328
329rmdir <path>
330 Calls rmdir(2) on the given path.
331
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700332setprop <name> <value>
Elliott Hughesf682b472015-02-06 12:19:48 -0800333 Set system property <name> to <value>. Properties are expanded
334 within <value>.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700335
336setrlimit <resource> <cur> <max>
337 Set the rlimit for a resource.
338
339start <service>
340 Start a service running if it is not already running.
341
342stop <service>
343 Stop a service from running if it is currently running.
344
Elliott Hughes91a3be52015-03-20 11:00:15 -0700345swapon_all <fstab>
346 Calls fs_mgr_swapon_all on the given fstab file.
347
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700348symlink <target> <path>
349 Create a symbolic link at <path> with the value <target>
350
The Android Open Source Project35237d12008-12-17 18:08:08 -0800351sysclktz <mins_west_of_gmt>
352 Set the system clock base (0 if system clock ticks in GMT)
353
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700354trigger <event>
355 Trigger an event. Used to queue an action from another
356 action.
357
Alex Light68ab20f2016-06-23 11:11:39 -0700358umount <path>
359 Unmount the filesystem mounted at that path.
360
Elliott Hughes91a3be52015-03-20 11:00:15 -0700361verity_load_state
362 Internal implementation detail used to load dm-verity state.
363
364verity_update_state <mount_point>
365 Internal implementation detail used to update dm-verity state and
366 set the partition.<mount_point>.verified properties used by adb remount
367 because fs_mgr can't set them directly itself.
368
Patrick McCormick96d0a4d2011-02-04 10:51:39 -0800369wait <path> [ <timeout> ]
Elliott Hughes91a3be52015-03-20 11:00:15 -0700370 Poll for the existence of the given file and return when found,
371 or the timeout has been reached. If timeout is not specified it
372 currently defaults to five seconds.
Patrick McCormick96d0a4d2011-02-04 10:51:39 -0800373
Elliott Hughesf682b472015-02-06 12:19:48 -0800374write <path> <content>
375 Open the file at <path> and write a string to it with write(2).
376 If the file does not exist, it will be created. If it does exist,
377 it will be truncated. Properties are expanded within <content>.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700378
379
Tom Cherry3be66ed2015-09-01 14:49:38 -0700380Imports
381-------
382The import keyword is not a command, but rather its own section and is
383handled immediately after the .rc file that contains it has finished
384being parsed. It takes the below form:
385
386import <path>
387 Parse an init config file, extending the current configuration.
388 If <path> is a directory, each file in the directory is parsed as
389 a config file. It is not recursive, nested directories will
390 not be parsed.
391
392There are only two times where the init executable imports .rc files,
393 1) When it imports /init.rc during initial boot
Hung-ying Tyandc738ea2016-01-14 11:18:21 +0800394 2) When it imports /{system,vendor,odm}/etc/init/ or .rc files at specified
395 paths during mount_all
Tom Cherry3be66ed2015-09-01 14:49:38 -0700396
397
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700398Properties
399----------
Tom Cherry3be66ed2015-09-01 14:49:38 -0700400Init provides information about the services that it is responsible
401for via the below properties.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700402
403init.svc.<name>
Tom Cherry3be66ed2015-09-01 14:49:38 -0700404 State of a named service ("stopped", "stopping", "running", "restarting")
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700405
406
Elliott Hughes841b2632015-02-12 14:28:54 -0800407Bootcharting
408------------
Elliott Hughes841b2632015-02-12 14:28:54 -0800409This version of init contains code to perform "bootcharting": generating log
410files that can be later processed by the tools provided by www.bootchart.org.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700411
Elliott Hughes59abac22015-03-28 12:12:51 -0700412On the emulator, use the -bootchart <timeout> option to boot with bootcharting
413activated for <timeout> seconds.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700414
Elliott Hughes841b2632015-02-12 14:28:54 -0800415On a device, create /data/bootchart/start with a command like the following:
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700416
Elliott Hughes841b2632015-02-12 14:28:54 -0800417 adb shell 'echo $TIMEOUT > /data/bootchart/start'
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700418
Elliott Hughes841b2632015-02-12 14:28:54 -0800419Where the value of $TIMEOUT corresponds to the desired bootcharted period in
420seconds. Bootcharting will stop after that many seconds have elapsed.
421You can also stop the bootcharting at any moment by doing the following:
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700422
Elliott Hughes841b2632015-02-12 14:28:54 -0800423 adb shell 'echo 1 > /data/bootchart/stop'
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700424
Elliott Hughes841b2632015-02-12 14:28:54 -0800425Note that /data/bootchart/stop is deleted automatically by init at the end of
426the bootcharting. This is not the case with /data/bootchart/start, so don't
427forget to delete it when you're done collecting data.
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700428
Elliott Hughes841b2632015-02-12 14:28:54 -0800429The log files are written to /data/bootchart/. A script is provided to
430retrieve them and create a bootchart.tgz file that can be used with the
431bootchart command-line utility:
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700432
Elliott Hughes841b2632015-02-12 14:28:54 -0800433 sudo apt-get install pybootchartgui
Elliott Hughes59abac22015-03-28 12:12:51 -0700434 # grab-bootchart.sh uses $ANDROID_SERIAL.
Elliott Hughes841b2632015-02-12 14:28:54 -0800435 $ANDROID_BUILD_TOP/system/core/init/grab-bootchart.sh
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700436
Elliott Hughes59abac22015-03-28 12:12:51 -0700437One thing to watch for is that the bootchart will show init as if it started
438running at 0s. You'll have to look at dmesg to work out when the kernel
439actually started init.
440
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700441
Ben Cheng50bbde02015-06-09 17:04:36 +0800442Comparing two bootcharts
443------------------------
444A handy script named compare-bootcharts.py can be used to compare the
445start/end time of selected processes. The aforementioned grab-bootchart.sh
446will leave a bootchart tarball named bootchart.tgz at /tmp/android-bootchart.
447If two such barballs are preserved on the host machine under different
448directories, the script can list the timestamps differences. For example:
449
450Usage: system/core/init/compare-bootcharts.py base_bootchart_dir
451 exp_bootchart_dir
452
453process: baseline experiment (delta)
454 - Unit is ms (a jiffy is 10 ms on the system)
455------------------------------------
456/init: 50 40 (-10)
457/system/bin/surfaceflinger: 4320 4470 (+150)
458/system/bin/bootanimation: 6980 6990 (+10)
459zygote64: 10410 10640 (+230)
460zygote: 10410 10640 (+230)
461system_server: 15350 15150 (-200)
462bootanimation ends at: 33790 31230 (-2560)
463
464
Yasuhiro Matsudaf93db4b2015-06-15 18:49:35 +0900465Systrace
466--------
467Systrace [1] can be used for obtaining performance analysis reports during boot
468time on userdebug or eng builds.
469Here is an example of trace events of "wm" and "am" categories:
470
471 $ANDROID_BUILD_TOP/external/chromium-trace/systrace.py wm am --boot
472
473This command will cause the device to reboot. After the device is rebooted and
474the boot sequence has finished, the trace report is obtained from the device
475and written as trace.html on the host by hitting Ctrl+C.
476
477LIMITATION
478Recording trace events is started after persistent properties are loaded, so
479the trace events that are emitted before that are not recorded. Several
480services such as vold, surfaceflinger, and servicemanager are affected by this
481limitation since they are started before persistent properties are loaded.
482Zygote initialization and the processes that are forked from the zygote are not
483affected.
484
485[1] http://developer.android.com/tools/help/systrace.html
486
487
Elliott Hughes841b2632015-02-12 14:28:54 -0800488Debugging init
489--------------
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700490By default, programs executed by init will drop stdout and stderr into
491/dev/null. To help with debugging, you can execute your program via the
Elliott Hughesf682b472015-02-06 12:19:48 -0800492Android program logwrapper. This will redirect stdout/stderr into the
The Android Open Source Project4f6e8d72008-10-21 07:00:00 -0700493Android logging system (accessed via logcat).
494
495For example
496service akmd /system/bin/logwrapper /sbin/akmd
Elliott Hughesf682b472015-02-06 12:19:48 -0800497
498For quicker turnaround when working on init itself, use:
499
Elliott Hughes841b2632015-02-12 14:28:54 -0800500 mm -j
Elliott Hughesf682b472015-02-06 12:19:48 -0800501 m ramdisk-nodeps
502 m bootimage-nodeps
503 adb reboot bootloader
504 fastboot boot $ANDROID_PRODUCT_OUT/boot.img
505
506Alternatively, use the emulator:
507
508 emulator -partition-size 1024 -verbose -show-kernel -no-window
509
510You might want to call klog_set_level(6) after the klog_init() call
511so you see the kernel logging in dmesg (or the emulator output).