Yolinux.com

inittab manpage

Search topic Section
Get manual page for the search topic
List all commands matching the search topic
List all topics in the manpage index

INITTAB(5)	      Linux System Administrator's Manual	    INITTAB(5)



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

DESCRIPTION
       The inittab file describes which processes are started  at  bootup  and
       during  normal  operation  (e.g. /etc/init.d/boot, /etc/init.d/rc, get-
       tys...).	 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:

	      id:runlevels:action:process

       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 cor-
	      responding  tty,	e.g. 1 for tty1. Some ancient login accounting
	      programs might expect this, though I can't think of any.

       runlevels
	      lists the runlevels for which the	 specified  action  should  be
	      taken.

       action describes which action should be taken.

       process
	      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 run-
       levels.	For example, 123 specifies that the process should be  started
       in  runlevels 1, 2, and 3.  The runlevels for ondemand entries may con-
       tain 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:

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

       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
	      entered.

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

       bootwait
	      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.

       ondemand
	      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
	      'c').

       initdefault
	      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.

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

       powerwait
	      The process will be executed when the power goes down.  Init  is
	      usually  informed	 about this by a process talking to a UPS con-
	      nected to the computer.  Init will wait for the process to  fin-
	      ish before continuing.

       powerfail
	      As  for  powerwait,  except that init does not wait for the pro-
	      cess's completion.

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

       powerfailnow
	      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).

       ctrlaltdel
	      The process will be executed when init receives the SIGINT  sig-
	      nal.   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.

       kbrequest
	      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 follow-
	      ing in your keymaps file:

	      alt keycode 103 = KeyboardSignal


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

	      # inittab for linux
	      id:1:initdefault:
	      rc::bootwait:/etc/rc
	      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
       tty1-tty4.

       A more elaborate inittab with different	runlevels  (see	 the  comments
       inside):

	      # Level to run in
	      id:2:initdefault:

	      # Boot-time system configuration/initialization script.
	      si::sysinit:/etc/rc.sysinit

	      # What to do in single-user mode.
	      ~:S:wait:/sbin/sulogin

	      # /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/rc 0
	      l1:1:wait:/etc/rc 1
	      l2:2:wait:/etc/rc 2
	      l3:3:wait:/etc/rc 3
	      l4:4:wait:/etc/rc 4
	      l5:5:wait:/etc/rc 5
	      l6:6:wait:/etc/rc 6

	      # What to do at the "3 finger salute".
	      ca::ctrlaltdel:/sbin/shutdown -t3 -r now

	      # Runlevel 2,3: getty on virtual consoles
	      # Runlevel   3: mgetty on terminal (ttyS0) and modem (ttyS1)
	      1:23:respawn:/sbin/mingetty tty1
	      2:23:respawn:/sbin/mingetty tty2
	      3:23:respawn:/sbin/mingetty tty3
	      4:23:respawn:/sbin/mingetty tty4
	      S0:3:respawn:/sbin/agetty ttyS0 9600 vt100-nav
	      S1:3:respawn:/sbin/mgetty -x0 -D ttyS1



FILES
       /etc/inittab

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

SEE ALSO
       init(8), telinit(8)



				  Dec 4, 2001			    INITTAB(5)
YoLinux.com Home Page
YoLinux Tutorial Index
Privacy Policy | Advertise with us | Feedback Form |
Unauthorized copying or redistribution prohibited.
    Bookmark and Share