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init(8)								      init(8)



NAME

  init - Process control initialization

SYNOPSIS

  /sbin/init  [0123456789MmQqSs]

OPTIONS

  0   Shuts down and halts the system.

  2   Changes the run level to a multiuser state with local processes and
      daemons.

  3   Changes the run level to a multiuser state with remote processes and
      daemons.

  1,4,5,6,7,8,9
      Changes run level	to that	specified by the number	option in the
      /etc/inittab file.  If no	such entry exists, no action is	taken and no
      message is output.

  Mm  Moves control to the console device and halts to single-user mode.

  Qq  Forces init to reexamine the entries in the inittab file and terminates
      any live processes which have had	their configuration entries removed
      from /etc/inittab.  Users	should be aware	that when a getty(8) line has
      been removed from/etc/inittab, and a login shell is active on the	ter-
      minal line that was formerly designated in inittab as a getty entry,
      the login	shell will be killed.

  Ss  Changes the run level to a single	user state with	only the essential
      kernel services.

DESCRIPTION

  The init program initializes the system by creating and controlling
  processes. The processes run by init at each run level are defined in	the
  inittab file.	The init program reads and processes the entries in the	init-
  tab file.

  The init program considers the system	to be in a run level at	any given
  time;	each run level has a specific group of processes that run at that
  level. The init program operates in one of eleven run	levels:	0-9 and	Ss.
  Of these, only -0, -s, -2, and -3 are	configured in the inittab file by
  default.

  The run level	changes	when a privileged user invokes init. The new init
  sends	appropriate signals to the original init that tell it which run	level
  to change to.


  Running the init program is the last step in the boot	process	after the
  root file system is mounted.	The init program scans the inittab file	and
  looks	for an entry with the initdefault keyword.  If the entry is there,
  init uses the	run level specified in that entry as the initial run level to
  enter. If the	entry is not found in the<filename> inittab</filename> file
  or if	the inittab file does not exist, init requests that the	user enter a
  run level from the system console, /dev/console. If the user enters the
  letter s, init enters	single user state, assigns the virtual console termi-
  nal to the user's terminal and opens it for reading and writing.  The	su
  command is invoked and the system displays a message on the console stating
  the location of the virtual console.

  To change the	run level, the user specifies either the 0, 2, 3, or s
  option.

  For the first	post-boot execution of init to a run level other than single
  user,	 it searches the inittab file for entries at the new run level that
  have the boot	or bootwait keywords.  If the run level	that is	specified
  matches the entry, the init program acts on these entries before processing
  other	entries	in the inittab file.  Any special initialization of the	sys-
  tem, such as checking	and mounting file systems, takes place before users
  are allowed on the system.  The init program then scans the inittab file to
  find all entries that	are to be handled for that level.

  Before starting a new	process, init reads each entry in the inittab file,
  and for each entry that should be respawned, init forks a child process.
  After	spawning all required processes, init waits for	one of its descendant
  processes to stop, a power-fail signal, or a signal that it should change
  the run level. If one	of the preceding three conditions occurs, init reex-
  amines the inittab file. You can add new entries to the inittab file,	but
  init does not	reexamine the file until one of	the three previous conditions
  actually occurs. To immediately reexamine the	inittab	file, invoke the init
  program with the q option.

FILES

  /sbin/init
      Specifies	the command path

  /etc/inittab
      Specifies	the init command control file

  /var/adm/wtmp
      Specifies	the permanent login accounting file

SEE ALSO

  Commands: getty(8), rc0(8), rc2(8), rc3(8), shutdown(8)

  Functions: kill(2), reboot(2)

  Files: inittab(4)