[sysvinit.git] / man / inittab.5

'\" -*- coding: UTF-8 -*-
.\" Copyright (C) 1998-2001 Miquel van Smoorenburg.
.\"
.\" This program is free software; you can redistribute it and/or modify
.\" it under the terms of the GNU General Public License as published by
.\" the Free Software Foundation; either version 2 of the License, or
.\" (at your option) any later version.
.\"
.\" This program is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public License
.\" along with this program; if not, write to the Free Software
.\" Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
.\"
.\"{{{}}}
.\"{{{  Title
.TH INITTAB 5 "Dec 4, 2001" "" "Linux System Administrator's Manual"
.\"}}}
.\"{{{  Name
.SH NAME
inittab \- format of the inittab file used by the sysv-compatible init
process
.\"}}}
.\"{{{  Description
.SH DESCRIPTION
The \fBinittab\fP file describes which processes are started at bootup and
during normal operation (e.g.\& /etc/init.d/boot, /etc/init.d/rc, gettys...).
.BR Init (8)
distinguishes multiple \fIrunlevels\fP, each of which can have its own set of
processes that are started.  Valid runlevels are \fB0\fP\-\fB6\fP plus
\fBA\fP, \fBB\fP, and \fBC\fP for \fBondemand\fP entries.  An entry in the
\fBinittab\fP file has the following format:
.RS
.sp
\fIid\fP:\fIrunlevels\fP:\fIaction\fP:\fIprocess\fP
.sp
.RE
Lines beginning with `#' are ignored.
.\"{{{  id
.IP \fIid\fP
is a unique sequence of 1-4 characters which identifies an entry in
.B inittab 
(for versions of sysvinit compiled with the \fIold\fP libc5 (< 5.2.18) or
a.out libraries the limit is 2 characters).
.sp
Note: traditionally, for getty and other login processes, the value of the
\fIid\fP field is kept the same as the suffix of the corresponding tty, e.g.\&
\fB1\fP for \fBtty1\fP. Some ancient login accounting programs might
expect this, though I can't think of any.
.\"}}}
.\"{{{  runlevels
.IP \fIrunlevels\fP
lists the runlevels for which the specified action should be taken.
.\"}}}
.\"{{{  action
.IP \fIaction\fP
describes which action should be taken.
.\"}}}
.\"{{{  process
.IP \fIprocess\fP
specifies the process to be executed.  If the process field starts with
a `+' character, 
.B 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.
.\"}}}
.PP
The \fIrunlevels\fP field may contain multiple characters for different
runlevels.  For example, \fB123\fP specifies that the process should be 
started in runlevels 1, 2, and 3.
The \fIrunlevels\fP for \fBondemand\fP entries may contain an \fBA\fP,
\fBB\fP, or \fBC\fP.  The \fIrunlevels\fP field of \fBsysinit\fP,
\fBboot\fP, and \fBbootwait\fP entries are ignored.
.PP
When the system runlevel is changed, any running processes that are not
specified for the new runlevel are killed, first with \s-2SIGTERM\s0,
then with \s-2SIGKILL\s0.
.PP
Valid actions for the \fIaction\fP field are:
.\"{{{  respawn
.IP \fBrespawn\fP
The process will be restarted whenever it terminates (e.g.\& getty).
.\"}}}
.\"{{{  wait
.IP \fBwait\fP
The process will be started once when the specified runlevel is entered and 
.B init 
will wait for its termination.
.\"}}}
.\"{{{  once
.IP \fBonce\fP
The process will be executed once when the specified runlevel is
entered.
.\"}}}
.\"{{{  boot
.IP \fBboot\fP
The process will be executed during system boot.  The \fIrunlevels\fP
field is ignored.
.\"}}}
.\"{{{  bootwait
.IP \fBbootwait\fP
The process will be executed during system boot, while 
.B init 
waits for its termination (e.g.\& /etc/rc).  
The \fIrunlevels\fP field is ignored.
.\"}}}
.\"{{{  off
.IP \fBoff\fP
This does nothing.
.\"}}}
.\"{{{  ondemand
.IP \fBondemand\fP
A process marked with an \fBondemand\fP runlevel will be executed
whenever the specified \fBondemand\fP runlevel is called.  However, no
runlevel change will occur (\fBondemand\fP runlevels are `a', `b',
and `c').
.\"}}}
.\"{{{  initdefault
.IP \fBinitdefault\fP
An \fBinitdefault\fP entry specifies the runlevel which should be
entered after system boot.  If none exists, 
.B init
will ask for a runlevel on the console. The \fIprocess\fP field is ignored.
.\"}}}
.\"{{{  sysinit
.IP \fBsysinit\fP
The process will be executed during system boot. It will be
executed before any \fBboot\fP or \fB bootwait\fP entries.
The \fIrunlevels\fP field is ignored.
.\"}}}
.\"{{{  powerwait
.IP \fBpowerwait\fP
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.
\fBInit\fP will wait for the process to finish before continuing.
.\"}}}
.\"{{{  powerfail
.IP \fBpowerfail\fP
As for \fBpowerwait\fP, except that \fBinit\fP does not wait for the process's
completion.
.\"}}}
.\"{{{  powerokwait
.IP \fBpowerokwait\fP
This process will be executed as soon as \fBinit\fP is informed that the
power has been restored.
.\"}}}
.\"{{{  powerfailnow
.IP \fBpowerfailnow\fP
This process will be executed when \fBinit\fP 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).
.\"}}}
.\"{{{  ctrlaltdel
.IP \fBctrlaltdel\fP
The process will be executed when \fBinit\fP receives the SIGINT signal.
This means that someone on the system console has pressed the
\fBCTRL\-ALT\-DEL\fP key combination. Typically one wants to execute some
sort of \fBshutdown\fP either to get into single\-user level or to
reboot the machine.
.\"}}}
.\"{{{  kbrequest
.IP \fBkbrequest\fP
The process will be executed when \fBinit\fP receives a signal from the
keyboard handler that a special key combination was pressed on the
console keyboard.
.sp
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:
.RS
.sp
alt keycode 103 = KeyboardSignal
.sp
.RE
.\"}}}
.\"}}}
.\"{{{  Examples
.SH EXAMPLES
This is an example of a inittab which resembles the old Linux inittab:
.RS
.sp
.nf
.ne 7
# inittab for linux
id:1:initdefault:
rc::bootwait:/etc/rc
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
.fi
.sp
.RE
This inittab file executes \fB/etc/rc\fP during boot and starts gettys
on tty1\-tty4.
.PP
A more elaborate \fBinittab\fP with different runlevels (see the comments
inside):
.RS
.sp
.nf
.ne 19
# Level to run in
id:2:initdefault:

# Boot-time system configuration/initialization script.
si::sysinit:/etc/init.d/rcS

# What to do in single-user mode.
~:S:wait:/sbin/sulogin

# /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.

l0:0:wait:/etc/init.d/rc 0
l1:1:wait:/etc/init.d/rc 1
l2:2:wait:/etc/init.d/rc 2
l3:3:wait:/etc/init.d/rc 3
l4:4:wait:/etc/init.d/rc 4
l5:5:wait:/etc/init.d/rc 5
l6:6:wait:/etc/init.d/rc 6

# 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

.fi
.sp
.RE
.\"}}}
.\"{{{  Files
.SH FILES
/etc/inittab
.\"}}}
.\"{{{  Author
.SH AUTHOR
\fBInit\fP was written by Miquel van Smoorenburg 
(miquels@cistron.nl).  This manual page was written by 
Sebastian Lederer (lederer@francium.informatik.uni-bonn.de) and modified
by Michael Haardt (u31b3hs@pool.informatik.rwth-aachen.de).
.\"}}}
.\"{{{  See also
.SH "SEE ALSO"
.BR init (8),
.BR telinit (8)
.\"}}}
Commit	Line	Data
a74aeac6 PR	1	'\" -- coding: UTF-8 --
	2	.\" Copyright (C) 1998-2001 Miquel van Smoorenburg.
	3	.\"
	4	.\" This program is free software; you can redistribute it and/or modify
	5	.\" it under the terms of the GNU General Public License as published by
	6	.\" the Free Software Foundation; either version 2 of the License, or
	7	.\" (at your option) any later version.
	8	.\"
	9	.\" This program is distributed in the hope that it will be useful,
	10	.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	.\" GNU General Public License for more details.
	13	.\"
	14	.\" You should have received a copy of the GNU General Public License
	15	.\" along with this program; if not, write to the Free Software
	16	.\" Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	17	.\"
	18	.\"{{{}}}
	19	.\"{{{ Title
	20	.TH INITTAB 5 "Dec 4, 2001" "" "Linux System Administrator's Manual"
	21	.\"}}}
	22	.\"{{{ Name
	23	.SH NAME
	24	inittab \- format of the inittab file used by the sysv-compatible init
	25	process
	26	.\"}}}
	27	.\"{{{ Description
	28	.SH DESCRIPTION
	29	The \fBinittab\fP file describes which processes are started at bootup and
	30	during normal operation (e.g.\& /etc/init.d/boot, /etc/init.d/rc, gettys...).
	31	.BR Init (8)
	32	distinguishes multiple \fIrunlevels\fP, each of which can have its own set of
	33	processes that are started. Valid runlevels are \fB0\fP\-\fB6\fP plus
	34	\fBA\fP, \fBB\fP, and \fBC\fP for \fBondemand\fP entries. An entry in the
	35	\fBinittab\fP file has the following format:
	36	.RS
	37	.sp
	38	\fIid\fP:\fIrunlevels\fP:\fIaction\fP:\fIprocess\fP
	39	.sp
	40	.RE
	41	Lines beginning with `#' are ignored.
	42	.\"{{{ id
	43	.IP \fIid\fP
	44	is a unique sequence of 1-4 characters which identifies an entry in
	45	.B inittab
	46	(for versions of sysvinit compiled with the \fIold\fP libc5 (< 5.2.18) or
	47	a.out libraries the limit is 2 characters).
	48	.sp
	49	Note: traditionally, for getty and other login processes, the value of the
	50	\fIid\fP field is kept the same as the suffix of the corresponding tty, e.g.\&
	51	\fB1\fP for \fBtty1\fP. Some ancient login accounting programs might
	52	expect this, though I can't think of any.
	53	.\"}}}
	54	.\"{{{ runlevels
	55	.IP \fIrunlevels\fP
	56	lists the runlevels for which the specified action should be taken.
	57	.\"}}}
	58	.\"{{{ action
	59	.IP \fIaction\fP
	60	describes which action should be taken.
	61	.\"}}}
	62	.\"{{{ process
	63	.IP \fIprocess\fP
	64	specifies the process to be executed. If the process field starts with
65	a `+' character,
66	.B init
67	will not do utmp and wtmp accounting for that process. This is needed for
68	gettys that insist on doing their own utmp/wtmp housekeeping. This is also
69	a historic bug.
70	.\"}}}
71	.PP
72	The \fIrunlevels\fP field may contain multiple characters for different
73	runlevels. For example, \fB123\fP specifies that the process should be
74	started in runlevels 1, 2, and 3.
75	The \fIrunlevels\fP for \fBondemand\fP entries may contain an \fBA\fP,
76	\fBB\fP, or \fBC\fP. The \fIrunlevels\fP field of \fBsysinit\fP,
77	\fBboot\fP, and \fBbootwait\fP entries are ignored.
78	.PP
79	When the system runlevel is changed, any running processes that are not
80	specified for the new runlevel are killed, first with \s-2SIGTERM\s0,
81	then with \s-2SIGKILL\s0.
82	.PP
83	Valid actions for the \fIaction\fP field are:
84	.\"{{{ respawn
85	.IP \fBrespawn\fP
86	The process will be restarted whenever it terminates (e.g.\& getty).
87	.\"}}}
88	.\"{{{ wait
89	.IP \fBwait\fP
90	The process will be started once when the specified runlevel is entered and
91	.B init
92	will wait for its termination.
93	.\"}}}
94	.\"{{{ once
95	.IP \fBonce\fP
96	The process will be executed once when the specified runlevel is
97	entered.
98	.\"}}}
99	.\"{{{ boot
100	.IP \fBboot\fP
101	The process will be executed during system boot. The \fIrunlevels\fP
102	field is ignored.
103	.\"}}}
104	.\"{{{ bootwait
105	.IP \fBbootwait\fP
106	The process will be executed during system boot, while
107	.B init
108	waits for its termination (e.g.\& /etc/rc).
109	The \fIrunlevels\fP field is ignored.
110	.\"}}}
111	.\"{{{ off
112	.IP \fBoff\fP
113	This does nothing.
114	.\"}}}
115	.\"{{{ ondemand
116	.IP \fBondemand\fP
117	A process marked with an \fBondemand\fP runlevel will be executed
118	whenever the specified \fBondemand\fP runlevel is called. However, no
119	runlevel change will occur (\fBondemand\fP runlevels are `a', `b',
120	and `c').
121	.\"}}}
122	.\"{{{ initdefault
123	.IP \fBinitdefault\fP
124	An \fBinitdefault\fP entry specifies the runlevel which should be
125	entered after system boot. If none exists,
126	.B init
127	will ask for a runlevel on the console. The \fIprocess\fP field is ignored.
128	.\"}}}
129	.\"{{{ sysinit
130	.IP \fBsysinit\fP
131	The process will be executed during system boot. It will be
132	executed before any \fBboot\fP or \fB bootwait\fP entries.
133	The \fIrunlevels\fP field is ignored.
134	.\"}}}
135	.\"{{{ powerwait
136	.IP \fBpowerwait\fP
137	The process will be executed when the power goes down. Init is usually
138	informed about this by a process talking to a UPS connected to the computer.
139	\fBInit\fP will wait for the process to finish before continuing.
140	.\"}}}
141	.\"{{{ powerfail
142	.IP \fBpowerfail\fP
143	As for \fBpowerwait\fP, except that \fBinit\fP does not wait for the process's
144	completion.
145	.\"}}}
146	.\"{{{ powerokwait
147	.IP \fBpowerokwait\fP
148	This process will be executed as soon as \fBinit\fP is informed that the
149	power has been restored.
150	.\"}}}
151	.\"{{{ powerfailnow
152	.IP \fBpowerfailnow\fP
153	This process will be executed when \fBinit\fP is told that the battery of
154	the external UPS is almost empty and the power is failing (provided that the
155	external UPS and the monitoring process are able to detect this condition).
156	.\"}}}
157	.\"{{{ ctrlaltdel
158	.IP \fBctrlaltdel\fP
159	The process will be executed when \fBinit\fP receives the SIGINT signal.
160	This means that someone on the system console has pressed the
161	\fBCTRL\-ALT\-DEL\fP key combination. Typically one wants to execute some
162	sort of \fBshutdown\fP either to get into single\-user level or to
163	reboot the machine.
164	.\"}}}
165	.\"{{{ kbrequest
166	.IP \fBkbrequest\fP
167	The process will be executed when \fBinit\fP receives a signal from the
168	keyboard handler that a special key combination was pressed on the
169	console keyboard.
170	.sp
171	The documentation for this function is not complete yet; more documentation
172	can be found in the kbd-x.xx packages (most recent was kbd-0.94 at
173	the time of this writing). Basically you want to map some keyboard
174	combination to the "KeyboardSignal" action. For example, to map Alt-Uparrow
175	for this purpose use the following in your keymaps file:
176	.RS
177	.sp
178	alt keycode 103 = KeyboardSignal
179	.sp
180	.RE
181	.\"}}}
182	.\"}}}
183	.\"{{{ Examples
184	.SH EXAMPLES
185	This is an example of a inittab which resembles the old Linux inittab:
186	.RS
187	.sp
188	.nf
189	.ne 7
190	# inittab for linux
191	id:1:initdefault:
192	rc::bootwait:/etc/rc
193	1:1:respawn:/etc/getty 9600 tty1
194	2:1:respawn:/etc/getty 9600 tty2
195	3:1:respawn:/etc/getty 9600 tty3
196	4:1:respawn:/etc/getty 9600 tty4
197	.fi
198	.sp
199	.RE
200	This inittab file executes \fB/etc/rc\fP during boot and starts gettys
201	on tty1\-tty4.
202	.PP
203	A more elaborate \fBinittab\fP with different runlevels (see the comments
204	inside):
205	.RS
206	.sp
207	.nf
208	.ne 19
209	# Level to run in
210	id:2:initdefault:
211
212	# Boot-time system configuration/initialization script.
213	si::sysinit:/etc/init.d/rcS
214
215	# What to do in single-user mode.
216	~:S:wait:/sbin/sulogin
217
218	# /etc/init.d executes the S and K scripts upon change
219	# of runlevel.
220	#
221	# Runlevel 0 is halt.
222	# Runlevel 1 is single-user.
223	# Runlevels 2-5 are multi-user.
224	# Runlevel 6 is reboot.
225
226	l0:0:wait:/etc/init.d/rc 0
227	l1:1:wait:/etc/init.d/rc 1
228	l2:2:wait:/etc/init.d/rc 2
229	l3:3:wait:/etc/init.d/rc 3
230	l4:4:wait:/etc/init.d/rc 4
231	l5:5:wait:/etc/init.d/rc 5
232	l6:6:wait:/etc/init.d/rc 6
233
234	# What to do at the "3 finger salute".
235	ca::ctrlaltdel:/sbin/shutdown -t1 -h now
236
237	# Runlevel 2,3: getty on virtual consoles
238	# Runlevel 3: getty on terminal (ttyS0) and modem (ttyS1)
239	1:23:respawn:/sbin/getty tty1 VC linux
240	2:23:respawn:/sbin/getty tty2 VC linux
241	3:23:respawn:/sbin/getty tty3 VC linux
242	4:23:respawn:/sbin/getty tty4 VC linux
243	S0:3:respawn:/sbin/getty -L 9600 ttyS0 vt320
244	S1:3:respawn:/sbin/mgetty -x0 -D ttyS1
245
246	.fi
247	.sp
248	.RE
249	.\"}}}
250	.\"{{{ Files
251	.SH FILES
252	/etc/inittab
253	.\"}}}
254	.\"{{{ Author
255	.SH AUTHOR
256	\fBInit\fP was written by Miquel van Smoorenburg
257	(miquels@cistron.nl). This manual page was written by
258	Sebastian Lederer (lederer@francium.informatik.uni-bonn.de) and modified
259	by Michael Haardt (u31b3hs@pool.informatik.rwth-aachen.de).
260	.\"}}}
261	.\"{{{ See also
262	.SH "SEE ALSO"
263	.BR init (8),
264	.BR telinit (8)
265	.\"}}}