[unix-history] / usr / man / man8 / init.8

.TH INIT 8 
.SH NAME
init, rc  \-  process control initialization
.SH SYNOPSIS
.B /etc/init
.br
.B /etc/rc
.SH DESCRIPTION
.I Init
is invoked as the last step of the boot procedure (see
.IR boot (8)).
Generally its role is to create a process for each
typewriter on which a user may log in.
.PP
When
.I init
first is executed
the console typewriter
.I /dev/console.
is opened for reading
and writing and the shell is invoked immediately.
This feature is used to bring up a single-user system.
If the shell terminates,
.I init
comes up multi-user and the process described below is started.
.PP
When
.I init
comes up multiuser,
it
invokes a shell, with input taken from the
file
.I /etc/rc.
This command file
performs housekeeping
like removing temporary files,
mounting file systems, and starting
daemons.
.PP
Then
.I init
reads the file
.I /etc/ttys
and
forks several times to create a process
for each typewriter specified in the file.
Each of these processes opens the appropriate typewriter
for reading and writing.  These channels thus
receive file descriptors 0, 1 and 2, the standard input,
output and error files.
Opening the typewriter will usually involve a delay,
since the
.IR open ""
is not completed until someone
is dialed up and carrier established on the channel.
Then
.I /etc/getty
is called with argument as specified by the last character of
the
.I ttys
file line.
.I Getty
reads the user's name and invokes
.IR login (1)
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.
Then the appropriate typewriter is reopened and
.I getty
is
reinvoked.
.PP
.I Init
catches the
hangup signal SIGHUP and interprets it to mean that
the
system should be brought from multi user to single
user.
Use `kill -1 1' to send the hangup signal.
.SH FILES
/dev/tty?, /etc/utmp, /usr/adm/wtmp, /etc/ttys, /etc/rc
.SH "SEE ALSO"
login(1), kill(1), sh(1), ttys(5), getty(8)
Commit	Line	Data
bc54062d KT	1	.TH INIT 8
	2	.SH NAME
	3	init, rc \- process control initialization
	4	.SH SYNOPSIS
	5	.B /etc/init
	6	.br
	7	.B /etc/rc
	8	.SH DESCRIPTION
	9	.I Init
	10	is invoked as the last step of the boot procedure (see
	11	.IR boot (8)).
	12	Generally its role is to create a process for each
	13	typewriter on which a user may log in.
	14	.PP
	15	When
	16	.I init
	17	first is executed
	18	the console typewriter
	19	.I /dev/console.
	20	is opened for reading
	21	and writing and the shell is invoked immediately.
	22	This feature is used to bring up a single-user system.
	23	If the shell terminates,
	24	.I init
	25	comes up multi-user and the process described below is started.
	26	.PP
	27	When
	28	.I init
	29	comes up multiuser,
	30	it
	31	invokes a shell, with input taken from the
	32	file
	33	.I /etc/rc.
	34	This command file
	35	performs housekeeping
	36	like removing temporary files,
	37	mounting file systems, and starting
	38	daemons.
	39	.PP
	40	Then
	41	.I init
	42	reads the file
	43	.I /etc/ttys
	44	and
	45	forks several times to create a process
	46	for each typewriter specified in the file.
	47	Each of these processes opens the appropriate typewriter
	48	for reading and writing. These channels thus
	49	receive file descriptors 0, 1 and 2, the standard input,
	50	output and error files.
	51	Opening the typewriter will usually involve a delay,
	52	since the
	53	.IR open ""
	54	is not completed until someone
	55	is dialed up and carrier established on the channel.
	56	Then
	57	.I /etc/getty
	58	is called with argument as specified by the last character of
	59	the
	60	.I ttys
	61	file line.
	62	.I Getty
	63	reads the user's name and invokes
	64	.IR login (1)
65	to log in the user and execute the shell.
66	.PP
67	Ultimately the shell will terminate
68	because of an end-of-file either
69	typed explicitly or generated as a result of hanging up.
70	The main path of
71	.IR init ,
72	which has been waiting
73	for such an event,
74	wakes up and removes the appropriate entry from the
75	file
76	.IR utmp ,
77	which records current users, and
78	makes an entry in
79	.IR /usr/adm/wtmp ,
80	which maintains a history
81	of logins and logouts.
82	Then the appropriate typewriter is reopened and
83	.I getty
84	is
85	reinvoked.
86	.PP
87	.I Init
88	catches the
89	hangup signal SIGHUP and interprets it to mean that
90	the
91	system should be brought from multi user to single
92	user.
93	Use `kill -1 1' to send the hangup signal.
94	.SH FILES
95	/dev/tty?, /etc/utmp, /usr/adm/wtmp, /etc/ttys, /etc/rc
96	.SH "SEE ALSO"
97	login(1), kill(1), sh(1), ttys(5), getty(8)