 |
Index for
Section 4 |
|
 |
Alphabetical
listing for I |
|
 |
Bottom of
page |
|
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.
SEE ALSO
Commands: init(8), getty(8)
Functions: kill(2)
|
Index for
Section 4 |
|
|
Alphabetical
listing for I |
|
 |
Top of
page |
|