inittab - format of the inittab file used by the sysv-compatible init process
file describes which processes are started at bootup and
during normal operation (e.g. /etc/init.d/boot, /etc/init.d/rc, gettys...).
(8) distinguishes multiple runlevels
, each of which can have
its own set of processes that are started. Valid runlevels are
, and C
entries. An entry in the inittab
file has the following format:
Lines beginning with `#' are ignored.
- 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
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.
- lists the runlevels for which the specified action should
- describes which action should be taken.
- 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
length of this field is limited to 127 characters.
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
entries may contain an A
, or C
. The runlevels
field of sysinit
, 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
Valid actions for the action
- The process will be restarted whenever it terminates (e.g.
- The process will be started once when the specified
runlevel is entered and init will wait for its termination.
- The process will be executed once when the specified
runlevel is entered.
- The process will be executed during system boot. The
runlevels field is ignored.
- The process will be executed during system boot, while
init waits for its termination (e.g. /etc/rc). The runlevels
field is ignored.
- This does nothing.
- 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').
- 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.
- The process will be executed during system boot. It will be
executed before any boot or bootwait entries. The
runlevels field is ignored.
- 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
- As for powerwait, except that init does not
wait for the process's completion.
- This process will be executed as soon as init is
informed that the power has been restored.
- 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).
- 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.
- 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
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
A more elaborate inittab
with different runlevels (see the comments
# Level to run in
# Boot-time system configuration/initialization script.
# What to do in single-user mode.
# /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.
# 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
was written by Miquel van Smoorenburg (firstname.lastname@example.org). This
manual page was written by Sebastian Lederer
(email@example.com) and modified by Michael Haardt