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Android Init Language --------------------- The Android Init Language consists of four broad classes of statements, which are Actions, Commands, Services, and Options. All of these are line-oriented, consisting of tokens separated by whitespace. The c-style backslash escapes may be used to insert whitespace into a token. Double quotes may also be used to prevent whitespace from breaking text into multiple tokens. The backslash, when it is the last character on a line, may be used for line-folding. Lines which start with a # (leading whitespace allowed) are comments. Actions and Services implicitly declare a new section. All commands or options belong to the section most recently declared. Commands or options before the first section are ignored. Actions and Services have unique names. If a second Action or Service is declared with the same name as an existing one, it is ignored as an error. (??? should we override instead) Actions ------- Actions are named sequences of commands. Actions have a trigger which is used to determine when the action should occur. When an event occurs which matches an action's trigger, that action is added to the tail of a to-be-executed queue (unless it is already on the queue). Each action in the queue is dequeued in sequence and each command in that action is executed in sequence. Init handles other activities (device creation/destruction, property setting, process restarting) "between" the execution of the commands in activities. Actions take the form of: on <trigger> <command> <command> <command> Services -------- Services are programs which init launches and (optionally) restarts when they exit. Services take the form of: service <name> <pathname> [ <argument> ]* <option> <option> ... Options ------- Options are modifiers to services. They affect how and when init runs the service. critical This is a device-critical service. If it exits more than four times in four minutes, the device will reboot into recovery mode. disabled This service will not automatically start with its class. It must be explicitly started by name. setenv <name> <value> Set the environment variable <name> to <value> in the launched process. socket <name> <type> <perm> [ <user> [ <group> [ <seclabel> ] ] ] Create a unix domain socket named /dev/socket/<name> and pass its fd to the launched process. <type> must be "dgram", "stream" or "seqpacket". User and group default to 0. 'seclabel' is the SELinux security context for the socket. It defaults to the service security context, as specified by seclabel or computed based on the service executable file security context. user <username> Change to username before exec'ing this service. Currently defaults to root. (??? probably should default to nobody) Currently, if your process requires linux capabilities then you cannot use this command. You must instead request the capabilities in-process while still root, and then drop to your desired uid. group <groupname> [ <groupname> ]* Change to groupname before exec'ing this service. Additional groupnames beyond the (required) first one are used to set the supplemental groups of the process (via setgroups()). Currently defaults to root. (??? probably should default to nobody) seclabel <seclabel> Change to 'seclabel' before exec'ing this service. Primarily for use by services run from the rootfs, e.g. ueventd, adbd. Services on the system partition can instead use policy-defined transitions based on their file security context. If not specified and no transition is defined in policy, defaults to the init context. oneshot Do not restart the service when it exits. class <name> Specify a class name for the service. All services in a named class may be started or stopped together. A service is in the class "default" if one is not specified via the class option. onrestart Execute a Command (see below) when service restarts. writepid <file...> Write the child's pid to the given files when it forks. Meant for cgroup/cpuset usage. Triggers -------- Triggers are strings which can be used to match certain kinds of events and used to cause an action to occur. boot This is the first trigger that will occur when init starts (after /init.conf is loaded) <name>=<value> Triggers of this form occur when the property <name> is set to the specific value <value>. One can also test multiple properties to execute a group of commands. For example: on property:test.a=1 && property:test.b=1 setprop test.c 1 The above stub sets test.c to 1 only when both test.a=1 and test.b=1 Commands -------- bootchart_init Start bootcharting if configured (see below). This is included in the default init.rc. chmod <octal-mode> <path> Change file access permissions. chown <owner> <group> <path> Change file owner and group. class_start <serviceclass> Start all services of the specified class if they are not already running. class_stop <serviceclass> Stop and disable all services of the specified class if they are currently running. class_reset <serviceclass> Stop all services of the specified class if they are currently running, without disabling them. They can be restarted later using class_start. copy <src> <dst> Copies a file. Similar to write, but useful for binary/large amounts of data. domainname <name> Set the domain name. enable <servicename> Turns a disabled service into an enabled one as if the service did not specify disabled. If the service is supposed to be running, it will be started now. Typically used when the bootloader sets a variable that indicates a specific service should be started when needed. E.g. on property:ro.boot.myfancyhardware=1 enable my_fancy_service_for_my_fancy_hardware exec [ <seclabel> [ <user> [ <group> ]* ] ] -- <command> [ <argument> ]* Fork and execute command with the given arguments. The command starts after "--" so that an optional security context, user, and supplementary groups can be provided. No other commands will be run until this one finishes. <seclabel> can be a - to denote default. export <name> <value> Set the environment variable <name> equal to <value> in the global environment (which will be inherited by all processes started after this command is executed) hostname <name> Set the host name. ifup <interface> Bring the network interface <interface> online. import <filename> Parse an init config file, extending the current configuration. insmod <path> Install the module at <path> load_all_props Loads properties from /system, /vendor, et cetera. This is included in the default init.rc. load_persist_props Loads persistent properties when /data has been decrypted. This is included in the default init.rc. loglevel <level> Sets the kernel log level to level. Properties are expanded within <level>. mkdir <path> [mode] [owner] [group] Create a directory at <path>, optionally with the given mode, owner, and group. If not provided, the directory is created with permissions 755 and owned by the root user and root group. If provided, the mode, owner and group will be updated if the directory exists already. mount_all <fstab> Calls fs_mgr_mount_all on the given fs_mgr-format fstab. mount <type> <device> <dir> [ <flag> ]* [<options>] Attempt to mount the named device at the directory <dir> <device> may be of the form mtd@name to specify a mtd block device by name. <flag>s include "ro", "rw", "remount", "noatime", ... <options> include "barrier=1", "noauto_da_alloc", "discard", ... as a comma separated string, eg: barrier=1,noauto_da_alloc powerctl Internal implementation detail used to respond to changes to the "sys.powerctl" system property, used to implement rebooting. restart <service> Like stop, but doesn't d