inittab(4)inittab(4)NAMEinittab - Controls the initialization process
SYNOPSIS
/etc/inittab
DESCRIPTION
The inittab file provides the init program with instructions for creat‐
ing and running initialization processes. The init program reads the
inittab file each time init is invoked. The file typically contains
instructions for the default initialization, the creation and control
of processes at each run level, and the getty command, which controls
the activation of terminal lines.
Each line in the inittab file contains an entry that has four fields;
each field is separated by a colon. There is no limit to the number of
entries in the inittab file. The entry syntax is as follows: Identi‐
fier:Runlevel:Action:Command
Specifies a fourteen character field used to uniquely identify an
object. Specifies a twenty character field that defines the run levels
in which the object is to be processed. Runlevel corresponds to a con‐
figuration of processes in a system. Each process spawned by the init
command is assigned one or more run levels in which it is allowed to
exist. The run levels are as follows: Specifies the halt state. Spec‐
ifies multiuser state without network services. Specifies multiuser
state with network services. Specifies single-user state.
You can define multiple run levels for a process by specifying
more than one run level character in any combination. Specifies
a twenty character field that tells init how to treat the speci‐
fied process. init recognizes the following Action values:
Specifies that if the process does not exist or if it dies, init
starts it. If the process exists, init continues to process the
inittab file. Specifies that if init enters a run level that
matches the run level specified in the inittab file entry, it
starts the process and waits for its termination. As long as
init continues in this run level, it does not act on subsequent
reads of the entry in the inittab file. Specifies that if init
enters a run level that matches the run level specified in the
inittab file, it starts the process and does not wait for its
termination. When the process stops, init does not restart it.
If init enters a new run level where the process is still run‐
ning from a previous runlevel change, init does not restart the
process. Specifies that when init first executes and reads the
inittab file, it processes this entry. The init program starts
the process and does not wait for its termination. When the
process stops, init does not restart it. The run level specified
in this inittab file entry should be the default run level, or
it must match the run level in which init operates at boot time.
Specifies that when init first executes and reads the inittab
file, it processes this inittab file entry. The init program
starts the process, waits for its termination and, when it dies,
does not restart the process. (This value exists only for
SVID3/SVR4 compatibility.) Specifies that if init receives the
SIGPWR power fail signal, it executes the process associated
with this line. (This value exists only for SVID3/SVR4 compati‐
bility.) Specifies that if init receives the SIGPWR power fail
signal, it executes the process associated with this line and
waits until the process terminates before continuing processing
the inittab file. Specifies that if the process associated with
this line is currently running, init sends the warning signal
SIGTERM and waits 20 seconds before sending the kill signal
SIGKILL. If the process does not existent, init ignores the
inittab entry. Specifies that a line with this action is pro‐
cessed when init is originally invoked. The init program uses
this line to determine the run level to enter originally. It
determines this by taking the highest run level specified in the
run level field and using that as its initial state. If the run
level field is empty, this is interpreted as 0s23, causing init
to enter run level 3. If init does not find an initdefault
entry in the inittab file, it requests an initial run level from
the operator. Specifies that entries of this type are executed
before init tries to access the console. This inittab file entry
should be used only to initialize devices on which init could
attempt to request a run level. Specifies a 1024 character
field that contains the sh command to be executed. The command
is prefixed with exec. Any legitimate sh syntax can appear in
the command field. Comments can be inserted be specifying a num‐
ber sign (#). The line continuation character \ can be placed at
the end of a line.
EXAMPLES
The following is an example of an inittab file entry for a terminal
line:
tty01:23:respawn:/usr/sbin/getty /dev/tty08 9600 vt100
FILES
Specifies the command that initializes and controls terminal lines.
SEE ALSO
Commands: init(8), getty(8)
Functions: kill(2)inittab(4)