inittab

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/rc, get-
       tys...).  Init distinguishes multiple runlevels, of  which
       each  can  have its own set of processes that are started.
       Valid runlevels are 0-6  and  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  getty  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
              describes in which runlevels 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.

       Valid actions 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 runlevel field is ignored.

       bootwait
              The  process  will  be executed during system boot,
              while  init  waits  for   its   termination   (e.g.
              /etc/rc).  The runlevel 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 runlevel 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 powerwait, but init will not wait for  the  pro-
              cesses 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-0.91 at the time
              of this writing). Basically you want  to  map  some
              keyboard combination to the "Spawn_Console" action.
              For example to map Alt-Uparrow for this purpose use
              the following in your keymaps file:

              alt keycode 103 = Spawn_Console


       The  runlevel-field  may  contain  multiple characters for
       different runlevels, e.g. 123 if  the  process  should  be
       started  in  runlevels  1,  2 and 3.  ondemand-entries may
       contain an A, B or C.  The runlevel-field of sysinit, boot
       and bootwait entries are ignored.

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

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@drinkel.ow.org),  the  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)