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inittab(4)
NAME
inittab - Controls the initialization process
SYNOPSIS
/etc/inittab
DESCRIPTION
The inittab file provides the init program with instructions for creating
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:
Identifier:Runlevel:Action:Command
Indentifier
Specifies a fourteen character field used to uniquely identify an
object.
Runlevel Specifies a twenty character field that defines the run levels in
which the object is to be processed. Runlevel corresponds to a
configuration 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:
0 Specifies the halt state.
2 Specifies multiuser state without network services.
3 Specifies multiuser state with network services.
S or s Specifies single-user state.
You can define multiple run levels for a process by specifying more than
one run level character in any combination.
Action Specifies a twenty character field that tells init how to treat
the specified process. init recognizes the following Action
values:
respawn 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.
wait 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.
once 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
running from a previous runlevel change, init does not
restart the process.
boot 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.
bootwait 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.
powerfail (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.
powerwait (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 and waits until the process terminates before
continuing processing the inittab file.
off 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.
initdefault
Specifies that a line with this action is processed
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.
sysinit 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.
Command 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 number 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
/usr/sbin/getty
Specifies the command that initializes and controls terminal
lines.
RELATED INFORMATION
Commands: init(8), getty(8)
Functions: kill(2)