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NAME    [Toc]    [Back]

       inittab	-  format of the inittab file used by the sysv-compatible init

DESCRIPTION    [Toc]    [Back]

       The inittab file describes which processes are started  at  bootup  and
       during  normal  operation  (e.g. /etc/init.d/boot, /etc/init.d/rc, gettys...).
  Init(8) distinguishes multiple runlevels, each of  which  can
       have  its  own  set of processes that are started.  Valid runlevels are
       0-6 plus A, B, and C for ondemand entries.  An  entry  in  the  inittab
       file has the following format:


       Lines beginning with `#' are ignored.

       id     is a unique sequence of 1-4 characters which identifies an entry
	      in inittab (for versions of sysvinit compiled with the old libc5
	      (< 5.2.18) or a.out libraries the limit is 2 characters).

	      Note:  traditionally,  for  getty and other login processes, the
	      value of the id field is kept the same as the suffix of the corresponding
  tty,	e.g. 1 for tty1. Some ancient login accounting
	      programs might expect this, though I can't think of any.

	      lists the runlevels for which the  specified  action  should  be

       action describes which action should be taken.

	      specifies  the  process  to  be  executed.  If the process field
	      starts with a `+' character, init will  not  do  utmp  and  wtmp
	      accounting  for  that  process.	This is needed for gettys that
	      insist on doing their own utmp/wtmp housekeeping.  This is  also
	      a historic bug.

       The  runlevels field may contain multiple characters for different runlevels.
	For example, 123 specifies that the process should be  started
       in  runlevels 1, 2, and 3.  The runlevels for ondemand entries may contain
 an A, B, or C.  The runlevels field of sysinit, boot, and bootwait
       entries are ignored.

       When the system runlevel is changed, any running processes that are not
       specified for the new runlevel are killed,  first  with	SIGTERM,  then
       with SIGKILL.

       Valid actions for the action field are:

	      The  process  will  be  restarted  whenever  it terminates (e.g.

       wait   The process will be started once when the specified runlevel  is
	      entered and init will wait for its termination.

       once   The process will be executed once when the specified runlevel is

       boot   The process will be executed during system boot.	The  runlevels
	      field is ignored.

	      The  process  will  be  executed	during system boot, while init
	      waits for its termination (e.g. /etc/rc).  The  runlevels  field
	      is ignored.

       off    This does nothing.

	      A  process  marked  with	an  ondemand runlevel will be executed
	      whenever the specified ondemand runlevel is called.  However, no
	      runlevel change will occur (ondemand runlevels are `a', `b', and

	      An initdefault entry specifies  the  runlevel  which  should  be
	      entered  after system boot.  If none exists, init will ask for a
	      runlevel on the console. The process field is ignored.

	      The process will be executed during system boot. It will be executed
 before any boot or	bootwait entries.  The runlevels field
	      is ignored.

	      The process will be executed when the power goes down.  Init  is
	      usually  informed  about this by a process talking to a UPS connected
 to the computer.  Init will wait for the process to  finish
 before continuing.

	      As  for  powerwait,  except  that  init  does  not  wait for the
	      process's completion.

	      This process will be executed as soon  as  init  is  informormed
	      that the power has been restored.

	      This process will be executed when init is told that the battery
	      of the external UPS is almost empty and  the  power  is  failing
	      (provided  that  the external UPS and the monitoring process are
	      able to detect this condition).

	      The process will be executed when init receives the SIGINT  signal.
   This means that someone on the system console has pressed
	      the CTRL-ALT-DEL key combination. Typically one wants to execute
	      some sort of shutdown either to get into single-user level or to
	      reboot the machine.

	      The process will be executed when init receives  a  signal  from
	      the  keyboard handler that a special key combination was pressed
	      on the console keyboard.

	      The documentation for this function is not  complete  yet;  more
	      documentation can be found in the kbd-x.xx packages (most recent
	      was kbd-0.94 at the time of this writing). Basically you want to
	      map  some  keyboard  combination to the "KeyboardSignal" action.
	      For example, to map Alt-Uparrow for this purpose use the following
 in your keymaps file:

	      alt keycode 103 = KeyboardSignal

EXAMPLES    [Toc]    [Back]

       This is an example of a inittab which resembles the old Linux inittab:

	      # inittab for linux
	      1:1:respawn:/etc/getty 9600 tty1
	      2:1:respawn:/etc/getty 9600 tty2
	      3:1:respawn:/etc/getty 9600 tty3
	      4:1:respawn:/etc/getty 9600 tty4

       This  inittab  file  executes  /etc/rc during boot and starts gettys on

       A more elaborate inittab with different	runlevels  (see  the  comments

	      # Level to run in

	      # Boot-time system configuration/initialization script.

	      # What to do in single-user mode.

	      # /etc/init.d executes the S and K scripts upon change
	      # of runlevel.
	      # Runlevel 0 is halt.
	      # Runlevel 1 is single-user.
	      # Runlevels 2-5 are multi-user.
	      # Runlevel 6 is reboot.

	      l0:0:wait:/etc/init.d/rc 0
	      l1:1:wait:/etc/init.d/rc 1
	      l2:2:wait:/etc/init.d/rc 2
	      l3:3:wait:/etc/init.d/rc 3
	      l4:4:wait:/etc/init.d/rc 4
	      l5:5:wait:/etc/init.d/rc 5
	      l6:6:wait:/etc/init.d/rc 6

	      # What to do at the "3 finger salute".
	      ca::ctrlaltdel:/sbin/shutdown -t1 -h now

	      # Runlevel 2,3: getty on virtual consoles
	      # Runlevel   3: getty on terminal (ttyS0) and modem (ttyS1)
	      1:23:respawn:/sbin/getty tty1 VC linux
	      2:23:respawn:/sbin/getty tty2 VC linux
	      3:23:respawn:/sbin/getty tty3 VC linux
	      4:23:respawn:/sbin/getty tty4 VC linux
	      S0:3:respawn:/sbin/getty -L 9600 ttyS0 vt320
	      S1:3:respawn:/sbin/mgetty -x0 -D ttyS1

FILES    [Toc]    [Back]


AUTHOR    [Toc]    [Back]

       Init  was written by Miquel van Smoorenburg (miquels@cistron.nl).  This
       manual page was written by Sebastian  Lederer  (lederer@francium.informatik.uni-bonn.de)
  and modified by Michael Haardt (u31b3hs@pool.informatik.rwth-aachen.de).

SEE ALSO    [Toc]    [Back]

       init(8), telinit(8)

				  Dec 4, 2001			    INITTAB(5)
[ Back ]
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