[unix-history] / usr / src / old / init / init.8

.\" Copyright (c) 1980 Regents of the University of California.
.\" All rights reserved.  The Berkeley software License Agreement
.\" specifies the terms and conditions for redistribution.
.\"
.\"	@(#)init.8	6.1 (Berkeley) %G%
.\"
.TH INIT 8 ""
.UC 4
.SH NAME
init \- process control initialization
.SH SYNOPSIS
.B /etc/init
.SH DESCRIPTION
.I Init
is invoked inside UNIX as the last step in the boot procedure.
It normally then runs the automatic reboot sequence as described in
.IR reboot (8),
and if this succeeds, begins multi-user operation.
If the reboot fails, it commences single user operation by giving
the super-user a shell on the console.  It is possible to pass parameters
from the boot program to
.I init
so that single user operation is commenced immediately.
When such single user operation is terminated by killing the single-user
shell (i.e. by hitting ^D),
.I init
runs
.I /etc/rc
without the reboot parameter.
This command file
performs housekeeping operations
such as removing temporary files,
mounting file systems, and starting
daemons.
.PP
In multi-user operation, 
.I init's
role is to create a process for each
terminal port on which a user may log in.
To begin such operations, it reads the file
.I /etc/ttys
and
executes a command for each terminal specified in the file.
This command will usually be
.IR /etc/getty .
.I Getty
reads the user's name and invokes
.I login
to log in the user and execute the Shell.
.PP
Ultimately the Shell will terminate
because of an end-of-file either
typed explicitly or generated as a result of hanging up.
The main path of
.IR init ,
which has been waiting
for such an event,
wakes up and removes the appropriate entry from the
file
.IR utmp ,
which records current users, and
makes an entry in
.IR /usr/adm/wtmp ,
which maintains a history
of logins and logouts.
The
.I wtmp
entry is made only if a user logged in successfully on the line.
Then the appropriate terminal is reopened and
.I getty
is
reinvoked.
.PP
.I Init
catches the
.I hangup
signal (signal SIGHUP) and interprets it to mean that
the file
.I /etc/ttys
should be read again.
The Shell process on each line which used to be active
in
.I ttys
but is no longer there is terminated;
a new process is created for each added line;
lines unchanged in the file are undisturbed.
Thus it is possible to drop or add phone lines without
rebooting the system by changing the
.I ttys
file and sending a
.I hangup
signal to the
.I init
process: use `kill \-HUP 1.'
.PP
.I Init
will terminate multi-user operations and resume single-user mode
if sent a terminate (TERM) signal, i.e. ``kill \-TERM 1''.
If there are processes outstanding which are deadlocked (due to
hardware or software failure),
.I init
will not wait for them all to die (which might take forever), but
will time out after 30 seconds and print a warning message.
.PP
.I Init
will cease creating new
.IR getty 's
and allow the system to slowly die away, if it is sent a terminal stop (TSTP)
signal, i.e. ``kill \-TSTP 1''.  A later hangup will resume full
multi-user operations, or a terminate will initiate a single user shell.
This hook is used by
.IR reboot (8)
and
.IR halt (8).
.PP
.I Init's
role is so critical that if it dies, the system will reboot itself
automatically.
If, at bootstrap time, the
.I init
process cannot be located, the system will loop in user mode at location
0x13.
.SH DIAGNOSTICS
\fBinit: \fR\fItty\fR\|\fB: cannot open\fR.  A terminal which is turned
on in the \fIrc\fR file cannot be opened, likely because the requisite
lines are either not configured into the system or the associated device
was not attached during boot-time system configuration.
.LP
\fBWARNING: Something is hung (wont die); ps axl advised\fR.  A process
is hung and could not be killed when the system was shutting down.
This is usually caused by a process
which is stuck in a device driver due to a persistent device error condition.
.SH FILES
/dev/console,
/dev/tty*,
/etc/utmp,
/usr/adm/wtmp,
/etc/ttys,
/etc/rc
.SH "SEE ALSO"
login(1), kill(1), sh(1), ttys(5), crash(8V), getty(8), rc(8), reboot(8),
halt(8), shutdown(8)
Commit	Line	Data
b891f6cd KM	1	.\" Copyright (c) 1980 Regents of the University of California.
	2	.\" All rights reserved. The Berkeley software License Agreement
	3	.\" specifies the terms and conditions for redistribution.
	4	.\"
7f53c63b	5	.\" @(#)init.8 6.1 (Berkeley) %G%
b891f6cd	6	.\"
7f53c63b	7	.TH INIT 8 ""
b891f6cd KM	8	.UC 4
	9	.SH NAME
	10	init \- process control initialization
	11	.SH SYNOPSIS
	12	.B /etc/init
	13	.SH DESCRIPTION
	14	.I Init
	15	is invoked inside UNIX as the last step in the boot procedure.
	16	It normally then runs the automatic reboot sequence as described in
	17	.IR reboot (8),
	18	and if this succeeds, begins multi-user operation.
	19	If the reboot fails, it commences single user operation by giving
	20	the super-user a shell on the console. It is possible to pass parameters
	21	from the boot program to
	22	.I init
	23	so that single user operation is commenced immediately.
	24	When such single user operation is terminated by killing the single-user
	25	shell (i.e. by hitting ^D),
	26	.I init
	27	runs
	28	.I /etc/rc
	29	without the reboot parameter.
	30	This command file
	31	performs housekeeping operations
	32	such as removing temporary files,
	33	mounting file systems, and starting
	34	daemons.
	35	.PP
	36	In multi-user operation,
	37	.I init's
	38	role is to create a process for each
	39	terminal port on which a user may log in.
	40	To begin such operations, it reads the file
	41	.I /etc/ttys
	42	and
7f53c63b KM	43	executes a command for each terminal specified in the file.
	44	This command will usually be
	45	.IR /etc/getty .
b891f6cd KM	46	.I Getty
	47	reads the user's name and invokes
	48	.I login
	49	to log in the user and execute the Shell.
	50	.PP
	51	Ultimately the Shell will terminate
	52	because of an end-of-file either
	53	typed explicitly or generated as a result of hanging up.
	54	The main path of
	55	.IR init ,
	56	which has been waiting
	57	for such an event,
	58	wakes up and removes the appropriate entry from the
	59	file
	60	.IR utmp ,
	61	which records current users, and
	62	makes an entry in
	63	.IR /usr/adm/wtmp ,
	64	which maintains a history
	65	of logins and logouts.
	66	The
	67	.I wtmp
	68	entry is made only if a user logged in successfully on the line.
	69	Then the appropriate terminal is reopened and
	70	.I getty
	71	is
	72	reinvoked.
	73	.PP
	74	.I Init
	75	catches the
	76	.I hangup
	77	signal (signal SIGHUP) and interprets it to mean that
	78	the file
	79	.I /etc/ttys
	80	should be read again.
	81	The Shell process on each line which used to be active
	82	in
	83	.I ttys
	84	but is no longer there is terminated;
	85	a new process is created for each added line;
	86	lines unchanged in the file are undisturbed.
	87	Thus it is possible to drop or add phone lines without
	88	rebooting the system by changing the
	89	.I ttys
	90	file and sending a
	91	.I hangup
	92	signal to the
	93	.I init
	94	process: use `kill \-HUP 1.'
	95	.PP
	96	.I Init
	97	will terminate multi-user operations and resume single-user mode
	98	if sent a terminate (TERM) signal, i.e. ``kill \-TERM 1''.
	99	If there are processes outstanding which are deadlocked (due to
	100	hardware or software failure),
	101	.I init
	102	will not wait for them all to die (which might take forever), but
	103	will time out after 30 seconds and print a warning message.
	104	.PP
	105	.I Init
	106	will cease creating new
	107	.IR getty 's
	108	and allow the system to slowly die away, if it is sent a terminal stop (TSTP)
	109	signal, i.e. ``kill \-TSTP 1''. A later hangup will resume full
110	multi-user operations, or a terminate will initiate a single user shell.
111	This hook is used by
112	.IR reboot (8)
113	and
114	.IR halt (8).
115	.PP
116	.I Init's
117	role is so critical that if it dies, the system will reboot itself
118	automatically.
119	If, at bootstrap time, the
120	.I init
121	process cannot be located, the system will loop in user mode at location
122	0x13.
123	.SH DIAGNOSTICS
124	\fBinit: \fR\fItty\fR\\|\fB: cannot open\fR. A terminal which is turned
125	on in the \fIrc\fR file cannot be opened, likely because the requisite
126	lines are either not configured into the system or the associated device
127	was not attached during boot-time system configuration.
128	.LP
129	\fBWARNING: Something is hung (wont die); ps axl advised\fR. A process
130	is hung and could not be killed when the system was shutting down.
131	This is usually caused by a process
132	which is stuck in a device driver due to a persistent device error condition.
133	.SH FILES
f2ba8c7e KM	134	/dev/console,
	135	/dev/tty*,
	136	/etc/utmp,
	137	/usr/adm/wtmp,
	138	/etc/ttys,
	139	/etc/rc
b891f6cd	140	.SH "SEE ALSO"
f2ba8c7e	141	login(1), kill(1), sh(1), ttys(5), crash(8V), getty(8), rc(8), reboot(8),
b891f6cd	142	halt(8), shutdown(8)