Index for Section 8

Alphabetical listing for I

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init(8)
NAME
  init - Process control initialization

SYNOPSIS
  /sbin/init [0123456789MmQqSs]

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
  inittab 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 inittab 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 terminal 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 flag.

  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
  system, 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
  reexamines 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 flag.




FLAGS
  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 flag 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 terminal 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.

FILES
  /sbin/init
	    Specifies the command path

  /etc/inittab
	    Specifies the init command control file

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

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

  Calls:  kill(2), reboot(2)

  Files:  inittab(4)

Index for Section 8

Alphabetical listing for I

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