INNITTAB
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 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 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
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 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
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
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