inittab - Controls the initialization process
/etc/inittab
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
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 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: Specifies
the halt state. Specifies 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 specified 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 running
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 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.
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 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.
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 number sign (#). The
line continuation character \ can be placed at the
end of a line.
The following is an example of an inittab file entry for a
terminal line:
tty01:23:respawn:/usr/sbin/getty /dev/tty08 9600 vt100
Specifies the command that initializes and controls terminal
lines.
Commands: init(8), getty(8)
Functions: kill(2)
inittab(4)
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