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init(1M)		System Administration Commands		      init(1M)

NAME
       init, telinit - process control initialization

SYNOPSIS
       /sbin/init [0123456abcQqSs]

       /etc/telinit [0123456abcQqSs]

DESCRIPTION
       init  is	 a general process spawner. Its	primary	role is	to create pro-
       cesses from information stored in the file /etc/inittab.

   Run Level Defined
       At any given time, the system is	in one of eight	possible run levels. A
       run level is a software configuration under which only a	selected group
       of processes exists. Processes spawned by init for each	of  these  run
       levels  are  defined  in	 /etc/inittab. init can	be in one of eight run
       levels, 0-6 and S or s (S and s are identical). The run	level  changes
       when  a privileged user runs /sbin/init.	This sends appropriate signals
       to the original init spawned by the operating system at boot time, say-
       ing which run level to invoke.

   init	and System Booting
       When  the  system  is booted, init is invoked and the following occurs.
       First, it reads /etc/default/init to set	environment variables. This is
       typically  where	TZ (time zone) and locale-related environments such as
       LANG or LC_CTYPE	get set. (See the FILES	section	at  the	 end  of  this
       page.)  init  then looks	in /etc/inittab	for the	initdefault entry (see
       inittab(4)). If the initdefault entry:

       exists
	     init usually uses the run level specified in that	entry  as  the
	     initial run level to enter.

       does not	exist
	     /etc/inittab,  init  asks	the user to enter a run	level from the
	     system console.

	     S or s
		   init	goes to	the single-user	state. In this state, the sys-
		   tem console device (/dev/console) is	opened for reading and
		   writing and the command /sbin/su, (see su(1M)), is invoked.
		   Use	either	init or	telinit	to change the run level	of the
		   system. Note	that if	the shell is terminated	(using an end-
		   of-file),   init  only  re-initializes  to  the single-user
		   state if /etc/inittab does not exist.

	     0-6   init	enters the corresponding run level. Run	levels	0,  5,
		   and 6 are reserved states for shutting the system down. Run
		   levels 2, 3,	and 4 are available  as	 multi-user  operating
		   states.

       If  this	 is  the first time since power	up that	init has entered a run
       level other than	single-user state, init	first scans  /etc/inittab  for
       boot and	bootwait entries (see inittab(4)). These entries are performed
       before any other	processing of /etc/inittab takes place,	providing that
       the  run	 level entered matches that of the entry. In this way any spe-
       cial initialization of the operating system, such as mounting file sys-
       tems,  can  take	 place	before users are allowed onto the system. init
       then scans /etc/inittab	and executes all other entries that are	to  be
       processed for that run level.

       To  spawn  each	process	in /etc/inittab, init reads each entry and for
       each entry that should be respawned, it forks a child process. After it
       has  spawned all	of the processes specified by /etc/inittab, init waits
       for one of its descendant processes to die, a powerfail	signal,	 or  a
       signal  from another init or telinit process to change the system's run
       level. When one of these	conditions occurs, init	re-examines /etc/init-
       tab.

   inittab Additions
       New  entries  can  be  added to /etc/inittab at any time; however, init
       still waits for one of the above	three conditions to occur  before  re-
       examining  /etc/inittab.	 To  get around	this, init Q or	init q command
       wakes init to re-examine	/etc/inittab immediately.

       When init comes up at boot time and whenever the	 system	 changes  from
       the  single-user	 state	to  another  run state,	init sets the ioctl(2)
       states  of  the	console	  to   those   modes   saved   in   the	  file
       /etc/ioctl.syscon. init writes this file	whenever the single-user state
       is entered.

   Run Level Changes
       When a run level	change request is made,	init sends the warning	signal
       (SIGTERM)  to all processes that	are undefined in the target run	level.
       init waits five seconds before forcibly terminating these processes  by
       sending a kill signal (SIGKILL).

       When  init  receives  a signal telling it that a	process	it spawned has
       died, it	records	the fact and the reason	it died	in /var/adm/utmpx  and
       /var/adm/wtmpx  if  it  exists (see who(1)). A history of the processes
       spawned is kept in /var/adm/wtmpx.

       If init receives	a powerfail signal (SIGPWR) it scans /etc/inittab  for
       special	entries	of the type powerfail and powerwait. These entries are
       invoked (if the run levels permit) before any further processing	 takes
       place. In this way init can perform various cleanup and recording func-
       tions during the	powerdown of the operating system.

   Environment Variables in /etc/defaults/init
       You can set default values for environment variables, for such items as
       timezone	 and character formatting, in /etc/default/init. See the FILES
       section,	below, for a list of these variables.

   telinit
       telinit,	which is linked	to /sbin/init, is used to direct  the  actions
       of init.	It takes a one-character argument and signals init to take the
       appropriate action.

SECURITY
       init uses pam(3PAM) for session management. The PAM configuration  pol-
       icy,  listed  through  /etc/pam.conf,  specifies	the session management
       module to be used for init.  Here  is  a	 partial  pam.conf  file  with
       entries for init	using the UNIX session management module.

       init   session	required    pam_unix_session.so.1

       If  there are no	entries	for the	init service, then the entries for the
       "other" service will be used.

OPTIONS
       0     Go	into firmware.

       1     Put the system in system administrator mode. All local file  sys-
	     tems  are mounted.	Only a small set of essential kernel processes
	     are left running. This mode is for	administrative tasks  such  as
	     installing	 optional  utility  packages. All files	are accessible
	     and no users are logged in	on the system.

       2     Put the system in multi-user  mode.  All  multi-user  environment
	     terminal  processes  and  daemons are spawned. This state is com-
	     monly referred to as the multi-user state.

       3     Extend multi-user mode by making local resources  available  over
	     the network.

       4     Is	 available to be defined as an alternative multi-user environ-
	     ment configuration. It is not necessary for system	operation  and
	     is	usually	not used.

       5     Shut  the	machine	 down  so that it is safe to remove the	power.
	     Have the machine remove power, if possible.

       6     Stop the operating	system and reboot to the state defined by  the
	     initdefault entry in /etc/inittab.

       a, b, c
	     process only those	/etc/inittab entries having the	a, b, or c run
	     level set.	These are pseudo-states, which may be defined  to  run
	     certain commands, but which do not	cause the current run level to
	     change.

       Q, q  Re-examine	/etc/inittab.

       S, s  Enter single-user mode. This is the only run level	 that  doesn't
	     require  the existence of a properly formatted /etc/inittab file.
	     If	this file does not exist, then by default, the only legal  run
	     level  that  init can enter is the	single-user mode. When in sin-
	     gle-user mode, the	filesystems required for basic	system	opera-
	     tion  will	 be mounted. When the system comes down	to single-user
	     mode, these file systems will remain mounted (even	if provided by
	     a	remote file server), and any other local filesystems will also
	     be	left mounted. During the transition down to single-user	 mode,
	     all  processes started by init or init.d scripts that should only
	     be	running	in  multi-user	mode  are  killed.  In	addition,  any
	     process  that  has	a utmpx	entry will be killed. This last	condi-
	     tion insures that all port	monitors started by the	SAC are	killed
	     and all services started by these port monitors, including	ttymon
	     login services, are killed.

FILES
       /dev/console
	     System console device.

       /etc/default/init
	     Contains environment variables  and  their	 default  values.  For
	     example,  for  the	 timezone  variable,  TZ,  you	might  specify
	     TZ=US/Pacific. The	variables are:

	     TZ	   Either specifies the	timezone information  (see  ctime(3C))
		   or	 the	name	of   a	 timezone   information	  file
		   /usr/share/lib/zoneinfo.

	     CMASK The mask (see umask(1))  that  init	uses  and  that	 every
		   process  inherits  from  the	init process. If not set, init
		   uses	the mask it inherits from the kernel. Note  that  init
		   always  attempts  to	apply a	umask of 022 before creating a
		   file, regardless of the setting of CMASK.

	     LC_CTYPE
		   Character characterization information.

	     LC_MESSAGES
		   Message translation.

	     LC_MONETARY
		   Monetary formatting information.

	     LC_NUMERIC
		   Numeric formatting information.

	     LC_TIME
		   Time	formatting information.

	     LC_ALL
		   If set, all other LC_* environmental	variables take-on this
		   value.

	     LANG  If  LC_ALL  is not set, and any particular LC_* is also not
		   set,	the value of LANG is used for that particular environ-
		   mental variable.

       /etc/initpipe
	     A named pipe used for internal communication.

       /etc/inittab
	     Controls process dispatching by init.

       /etc/ioctl.syscon
	     ioctl  states  of	the console, as	saved by init when single-user
	     state is entered.

       /var/adm/utmpx
	     User access and administration information.

       /var/adm/wtmpx
	     History of	user access and	administration information.

ATTRIBUTES
       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE	TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+

SEE ALSO
       login(1), sh(1),	stty(1),  who(1),  shutdown(1M),  su(1M),  ttymon(1M),
       ioctl(2),   kill(2),  ctime(3C),	 pam(3PAM),  inittab(4),  pam.conf(4),
       utmpx(4),  attributes(5),   pam_authtok_check(5),   pam_authtok_get(5),
       pam_authtok_store(5),  pam_dhkeys(5),  pam_passwd_auth(5), pam_unix(5),
       pam_unix_account(5), pam_unix_auth(5), pam_unix_session(5), termio(7I)

DIAGNOSTICS
       If init finds that it is	respawning an  entry  from  /etc/inittab  more
       than  ten  times	 in two	minutes, assumes that there is an error	in the
       command string in the entry, and	generates an error message on the sys-
       tem  console.  It  will	then refuse to respawn this entry until	either
       five minutes has	elapsed	or it receives a signal	 from  a  user-spawned
       init  or	 telinit.  This	 prevents init from eating up system resources
       when someone makes a typographical error	in the inittab file, or	a pro-
       gram is removed that is referenced in /etc/inittab.

NOTES
       init and	telinit	can be run only	by a privileged	user.

       The  S  or  s  state must not be	used indiscriminately in /etc/inittab.
       When modifying this file, it is best to avoid adding this state to  any
       line other than initdefault.

       If  a  default  state  is  not  specified  in  the initdefault entry in
       /etc/inittab, state 6 is	entered. Consequently, the system will loop by
       going to	firmware and rebooting continuously.

       If the utmpx file cannot	be created when	booting	the system, the	system
       will boot to state "s" regardless of the	state specified	in the initde-
       fault  entry in /etc/inittab. This can occur if the /var	file system is
       not accessible.

       When a system transitions down to the S or s  state,  the  /etc/nologin
       file  (see  nologin(4))	is created.  Upon subsequent transition	to run
       level 2,	this file is removed by	a script in the	/etc/rc2.d  directory.

       init uses /etc/initpipe,	a named	pipe, for internal communication.

       The pam_unix(5) module might not	be supported in	a future release. Sim-
       ilar  functionality  is	provided  by  pam_authtok_check(5),  pam_auth-
       tok_get(5),  pam_authtok_store(5),  pam_dhkeys(5),  pam_passwd_auth(5),
       pam_unix_account(5), pam_unix_auth(5), and pam_unix_session(5).

SunOS 5.9			  11 Dec 2001			      init(1M)

NAME | SYNOPSIS | DESCRIPTION | SECURITY | OPTIONS | FILES | ATTRIBUTES | SEE ALSO | DIAGNOSTICS | NOTES

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