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

NAME
       inittab - format of the inittab file used by the sysv-com-
       patible 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  multi-
       ple  runlevels, each of which can have its own set of pro-
       cesses 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  iden-
              tifies   an  entry  in  inittab  (for  versions  of
              sysvinit compiled with libraries < 5.2.18 or  a.out
              libraries the limit is 2 characters).

              Note:  For  gettys or other login processes, the id
              field should be the tty suffix of the corresponding
              tty,   e.g.  1  for  tty1.   Otherwise,  the  login
              accounting might not work correctly.

       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 pro-
              cess 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 termi-
              nates (e.g. getty).

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

       once   The process will be executed once when  the  speci-
              fied 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 con-
              sole. 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 init receives the
              SIGPWR  signal,  indicating that there is something
              wrong with the power. Init will wait for  the  pro-
              cess to finish before continuing.

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

       powerokwait
              The process will be executed when init receives the
              SIGPWR  signal,  provided  there  is  a file called
              /etc/powerstatus containing the word OK. This means
              that the power has come back again.

       ctrlaltdel
              The process will be executed when init receives the
              SIGINT signal.  This means that someone on the sys-
              tem console has pressed the CTRL-ALT-DEL key combi-
              nation. 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:

              # System initialization before anything else.
              si::sysinit:/etc/rc.d/bcheckrc

              # Runlevel 0,6 is halt and reboot, 1 is maintenance mode.
              l0:0:wait:/etc/rc.d/rc.halt
              l1:1:wait:/etc/rc.d/rc.single
              l2:2345:wait:/etc/rc.d/rc.multi
              l6:6:wait:/etc/rc.d/rc.reboot

              # What to do at the "3 finger salute".
              ca::ctrlaltdel:/sbin/shutdown -t5 -rf now

              # Runlevel 2&3: getty on console, level 3 also getty on modem port.
              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
              S2:3:respawn:/sbin/uugetty ttyS2 M19200

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)

                           Jul 16, 1997                         1