Provided by: sysvinit_2.86.ds1-59ubuntu13_i386 bug

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,
       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:

              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
              corresponding   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
       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:

       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
              executed 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
              connected  to  the  computer.  Init will wait for the process to
              finish before continuing.

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

       powerokwait
              This  process  will be executed as soon as init is informed 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
              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.

       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
              following 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/init.d/rcS

              # 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/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

       /etc/inittab

AUTHOR

       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

       init(8), telinit(8)

                                  Dec 4, 2001                       INITTAB(5)