rc(1M)																	    rc(1M)

NAME

       rc - general purpose sequencer invoked upon entering new run level

SYNOPSIS

DESCRIPTION

       The  shell script is the general sequencer invoked upon entering a new run level via the command (where N equals 0-6).  The script is typi-
       cally invoked by the corresponding entry in the file as follows:

       is the startup and shutdown sequencer script.  There is only one sequencer script and it handles all of the  sequencer  directories.   This
       script  sequences  the  scripts	in the appropriate sequencer directories in alphabetical order as defined by the shell and invokes them as
       either startup or kill scripts.

       If a transition from a lower to a higher run level (i.e., init state) occurs, the start scripts for the new run level and all  intermediate
       levels between the old and new level are executed.  If a transition from a higher to a lower run level occurs, the kill scripts for the new
       run level and all intermediate levels between the old and new level are executed.

       If a start script link (e.g., in sequencer N has a stop action, the corresponding kill script should be placed in sequencer (e.g.,  Actions
       started	in  level N should be stopped in level This way, a system shutdown (e.g., transition from level 3 directly to level 0) will result
       in all subsystems being stopped.

   Start and Kill Scripts
       In many cases, a startup script will have both a start and a kill action.  For example, the inetd script starts the Internet daemon in  the
       start  case,  and  kills that process in the stop case.	Instead of two separate scripts, only one exists, which accepts both the and argu-
       ments and executes the correct code.  In some cases, only a start action will be applicable.  If this is the case, and  if  the	action	is
       specified,  the	script should produce a usage message and exit with an error.  In general, scripts should look at their arguments and pro-
       duce error messages if bad arguments are present.  When a script executes properly, it must exit with a return value of zero.  If an  error
       condition exists, the return value must be nonzero.

   Naming Conventions
       The startup and shutdown scripts (referred to as startup scripts hereafter) exist in the directory, named after the subsystem they control.
       For example, the script controls starting up the daemon.  The contents of sequencer  directories  consist  of  symbolic	links  to  startup
       scripts in These symbolic links must follow a strict naming convention, as noted in the various fields of this example:

       where the fields are defined as follows:

	      The sequencer directory is numbered to reflect the
			     run  level  for  which its contents will be executed.  In this case, start scripts in this directory will be executed
			     upon entering run level 2 from run level 1, and kill scripts will be executed upon entering  run  level  2  from  run
			     level 3.

	      The first character of a sequencer link name determines
			     whether the script is executed as a start script (if the character is or as a kill script (if the character is

	      A three digit number is used for sequencing scripts within
			     the sequencer directory.  Scripts are executed by type (start or kill) in alphabetical order as defined by the shell.
			     Although it is not recommended, two scripts may share the same sequence number.

	      The name of the startup script follows the sequence number.
			     The startup script name must be the same name as the script to which this sequencer entry is linked.  In  this  exam-
			     ple, the link points to

			     Note  that  short file name systems require file names of 14 or less characters.  This means that the fourth field is
			     limited to 10 or fewer characters.

			     Scripts are executed in alphabetical order.  The entire file name of the script is  used  for  alphabetical  ordering
			     purposes.

			     When  ordering  start and kill script links, note that subsystems started in any given order should be stopped in the
			     reverse order to eliminate any dependencies between subsystems.  This means that kill scripts will generally not have
			     the same numbers as their start script counterparts.  For example, if two subsystems must be started in a given order
			     due to dependencies (e.g., followed by the kill counterparts to these scripts must be numbered so that the subsystems
			     are stopped in the opposite order in which they were started (e.g., followed by

			     Also  keep  in  mind  that  kill  scripts	for  a	start script in directory will reside in For example, and might be
			     start/kill counterparts.

   Arguments
       The startup/shutdown scripts should be able to recognize the following four arguments (where applicable):

	      The	     argument is passed to scripts whose names start with Upon receiving the argument, the script should perform its start
			     actions.

	      The	     argument  is passed to scripts whose names start with Upon receiving the argument, the script should perform its stop
			     actions.

	      The	     argument is passed to scripts whose names start with so that the script can report back a	short  message	indicating
			     what the start action will do.  For instance, when the spooler script is invoked with a argument, it echoes

			     This  string is used by the startup routines.  Scripts given just the argument will only print a message and not per-
			     form any actions.

	      The	     argument is passed to scripts whose names start with so that the script can report back a	short  message	indicating
			     what the stop action will do.  For instance, when the spooler script is invoked with a argument, it echoes

			     This  string  is  used  by the shutdown checklist.  Scripts given just the argument will only print a message and not
			     perform any actions.

   Script Output
       To ensure proper reporting of startup events, startup scripts are required to comply with the following guidelines for script output.

	      o  Status messages, such as

		 must be directed to stdout.  All error messages must be directed to stderr.

	      o  Script output, both stdout and stderr, is redirected to log file unless the startup checklist mode is set to the  raw	mode.	In
		 this case, all output goes to the console.  All error messages should be echoed to stdout or stderr.

	      o  Startup  scripts  are not allowed to send messages directly to the console, or to start any daemons that immediately write to the
		 console.  This restriction exists because these scripts are now started by the checklist wrapper.  All script output should go to
		 either stdout or stderr, and thus be captured in a log file.  Any console output will be garbled.

	      o  When  a startup script returns an exit code of can display a specific message on the console prior to rebooting the system.  This
		 is achieved by creating a text file named containing the text to be displayed to the console.	Note that deletes this file  after
		 displaying  the  message,  so startup scripts need to write this file each time a specific message is required to be displayed on
		 console prior to reboot.

RETURN VALUE

       The return values for startup scripts are as follows:

	      Script exited without error.
	      Script encountered errors.
	      Script was skipped due to overriding control variables
		   from files, or for other reasons, and did not actually do anything.
	      Script will automatically reboot the system.
	      Script exited without error and started a process in background mode.
	      For return values greater than
		   the action is same as return value script encountered errors.

SEE ALSO

       init(1M), shutdown(1M), inittab(4), rc.config(4).

																	    rc(1M)