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4 .\" This code is derived from software contributed to Berkeley by
5 .\" Donn Seeley at Berkeley Software Design, Inc.
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31 .\" @(#)init.8 8.3 (Berkeley) 4/18/94
32 .\" $FreeBSD$
33 .\"
34 .Dd September 15, 2005
35 .Dt INIT 8
36 .Os
37 .Sh NAME
38 .Nm init
39 .Nd process control initialization
40 .Sh SYNOPSIS
41 .Nm
42 .Nm
43 .Oo
44 .Cm 0 | 1 | 6 |
45 .Cm c | q
46 .Oc
47 .Sh DESCRIPTION
48 The
49 .Nm
50 utility
51 is the last stage of the boot process.
52 It normally runs the automatic reboot sequence as described in
53 .Xr rc 8 ,
54 and if this succeeds, begins multi-user operation.
55 If the reboot scripts fail,
56 .Nm
57 commences single-user operation by giving
58 the super-user a shell on the console.
59 The
60 .Nm
61 utility may be passed parameters
62 from the boot program to
63 prevent the system from going multi-user and to instead execute
64 a single-user shell without starting the normal daemons.
65 The system is then quiescent for maintenance work and may
66 later be made to go to multi-user by exiting the
67 single-user shell (with ^D).
68 This
69 causes
70 .Nm
71 to run the
72 .Pa /etc/rc
73 start up command file in fastboot mode (skipping disk checks).
74 .Pp
75 If the
76 .Em console
77 entry in the
78 .Xr ttys 5
79 file is marked
80 .Dq insecure ,
81 then
82 .Nm
83 will require that the super-user password be
84 entered before the system will start a single-user shell.
85 The password check is skipped if the
86 .Em console
87 is marked as
88 .Dq secure .
89 .Pp
90 If the system security level (see
91 .Xr security 7 )
92 is initially nonzero, then
93 .Nm
94 leaves it unchanged.
95 Otherwise,
96 .Nm
97 raises the level to 1 before going multi-user for the first time.
98 Since the level cannot be reduced, it will be at least 1 for
99 subsequent operation, even on return to single-user.
100 If a level higher than 1 is desired while running multi-user,
101 it can be set before going multi-user, e.g., by the startup script
102 .Xr rc 8 ,
103 using
104 .Xr sysctl 8
105 to set the
106 .Va kern.securelevel
107 variable to the required security level.
108 .Pp
109 If
110 .Nm
111 is run in a jail, the security level of the
112 .Dq host system
113 will not be affected.
114 Part of the information set up in the kernel to support a jail
115 is a per-jail security level.
116 This allows running a higher security level inside of a jail
117 than that of the host system.
118 See
119 .Xr jail 8
120 for more information about jails.
121 .Pp
122 In multi-user operation,
123 .Nm
124 maintains
125 processes for the terminal ports found in the file
126 .Xr ttys 5 .
127 The
128 .Nm
129 utility reads this file and executes the command found in the second field,
130 unless the first field refers to a device in
131 .Pa /dev
132 which is not configured.
133 The first field is supplied as the final argument to the command.
134 This command is usually
135 .Xr getty 8 ;
136 .Nm getty
137 opens and initializes the tty line
138 and
139 executes the
140 .Xr login 1
141 program.
142 The
143 .Nm login
144 program, when a valid user logs in,
145 executes a shell for that user.
146 When this shell
147 dies, either because the user logged out
148 or an abnormal termination occurred (a signal),
149 the
150 .Nm
151 utility wakes up, deletes the user
152 from the
153 .Xr utmp 5
154 file of current users and records the logout in the
155 .Xr wtmp 5
156 file.
157 The cycle is
158 then restarted by
159 .Nm
160 executing a new
161 .Nm getty
162 for the line.
163 .Pp
164 The
165 .Nm
166 utility can also be used to keep arbitrary daemons running,
167 automatically restarting them if they die.
168 In this case, the first field in the
169 .Xr ttys 5
170 file must not reference the path to a configured device node
171 and will be passed to the daemon
172 as the final argument on its command line.
173 This is similar to the facility offered in the
174 .At V
175 .Pa /etc/inittab .
176 .Pp
177 Line status (on, off, secure, getty, or window information)
178 may be changed in the
179 .Xr ttys 5
180 file without a reboot by sending the signal
181 .Dv SIGHUP
182 to
183 .Nm
184 with the command
185 .Dq Li "kill -HUP 1" .
186 On receipt of this signal,
187 .Nm
188 re-reads the
189 .Xr ttys 5
190 file.
191 When a line is turned off in
192 .Xr ttys 5 ,
193 .Nm
194 will send a SIGHUP signal to the controlling process
195 for the session associated with the line.
196 For any lines that were previously turned off in the
197 .Xr ttys 5
198 file and are now on,
199 .Nm
200 executes the command specified in the second field.
201 If the command or window field for a line is changed,
202 the change takes effect at the end of the current
203 login session (e.g., the next time
204 .Nm
205 starts a process on the line).
206 If a line is commented out or deleted from
207 .Xr ttys 5 ,
208 .Nm
209 will not do anything at all to that line.
210 However, it will complain that the relationship between lines
211 in the
212 .Xr ttys 5
213 file and records in the
214 .Xr utmp 5
215 file is out of sync,
216 so this practice is not recommended.
217 .Pp
218 The
219 .Nm
220 utility will terminate multi-user operations and resume single-user mode
221 if sent a terminate
222 .Pq Dv TERM
223 signal, for example,
224 .Dq Li "kill \-TERM 1" .
225 If there are processes outstanding that are deadlocked (because of
226 hardware or software failure),
227 .Nm
228 will not wait for them all to die (which might take forever), but
229 will time out after 30 seconds and print a warning message.
230 .Pp
231 The
232 .Nm
233 utility will cease creating new processes
234 and allow the system to slowly die away, if it is sent a terminal stop
235 .Pq Dv TSTP
236 signal, i.e.\&
237 .Dq Li "kill \-TSTP 1" .
238 A later hangup will resume full
239 multi-user operations, or a terminate will start a single-user shell.
240 This hook is used by
241 .Xr reboot 8
242 and
243 .Xr halt 8 .
244 .Pp
245 The
246 .Nm
247 utility will terminate all possible processes (again, it will not wait
248 for deadlocked processes) and reboot the machine if sent the interrupt
249 .Pq Dv INT
250 signal, i.e.\&
251 .Dq Li "kill \-INT 1".
252 This is useful for shutting the machine down cleanly from inside the kernel
253 or from X when the machine appears to be hung.
254 .Pp
255 The
256 .Nm
257 utility will do the same, except it will halt the machine if sent
258 the user defined signal 1
259 .Pq Dv USR1 ,
260 or will halt and turn the power off (if hardware permits) if sent
261 the user defined signal 2
262 .Pq Dv USR2 .
263 .Pp
264 When shutting down the machine,
265 .Nm
266 will try to run the
267 .Pa /etc/rc.shutdown
268 script.
269 This script can be used to cleanly terminate specific programs such
270 as
271 .Nm innd
272 (the InterNetNews server).
273 If this script does not terminate within 120 seconds,
274 .Nm
275 will terminate it.
276 The timeout can be configured via the
277 .Xr sysctl 8
278 variable
279 .Va kern.init_shutdown_timeout .
280 .Pp
281 The role of
282 .Nm
283 is so critical that if it dies, the system will reboot itself
284 automatically.
285 If, at bootstrap time, the
286 .Nm
287 process cannot be located, the system will panic with the message
288 .Dq "panic: init died (signal %d, exit %d)" .
289 .Pp
290 If run as a user process as shown in the second synopsis line,
291 .Nm
292 will emulate
293 .At V
294 behavior, i.e., super-user can specify the desired
295 .Em run-level
296 on a command line, and
297 .Nm
298 will signal the original
299 (PID 1)
300 .Nm
301 as follows:
302 .Bl -column Run-level SIGTERM
303 .It Sy "Run-level Signal Action
304 .It Cm 0 Ta Dv SIGUSR2 Ta "Halt and turn the power off"
305 .It Cm 1 Ta Dv SIGTERM Ta "Go to single-user mode"
306 .It Cm 6 Ta Dv SIGINT Ta "Reboot the machine"
307 .It Cm c Ta Dv SIGTSTP Ta "Block further logins"
308 .It Cm q Ta Dv SIGHUP Ta Rescan the
309 .Xr ttys 5
310 file
311 .El
312 .Sh FILES
313 .Bl -tag -width /etc/rc.shutdown -compact
314 .It Pa /dev/console
315 system console device
316 .It Pa /dev/tty*
317 terminal ports found in
318 .Xr ttys 5
319 .It Pa /var/run/utmp
320 record of current users on the system
321 .It Pa /var/log/wtmp
322 record of all logins and logouts
323 .It Pa /etc/ttys
324 the terminal initialization information file
325 .It Pa /etc/rc
326 system startup commands
327 .It Pa /etc/rc.shutdown
328 system shutdown commands
329 .El
330 .Sh DIAGNOSTICS
331 .Bl -diag
332 .It "getty repeating too quickly on port %s, sleeping."
333 A process being started to service a line is exiting quickly
334 each time it is started.
335 This is often caused by a ringing or noisy terminal line.
336 .Bf -emphasis
337 Init will sleep for 30 seconds,
338 then continue trying to start the process.
339 .Ef
340 .It "some processes would not die; ps axl advised."
341 A process
342 is hung and could not be killed when the system was shutting down.
343 This condition is usually caused by a process
344 that is stuck in a device driver because of
345 a persistent device error condition.
346 .El
347 .Sh SEE ALSO
348 .Xr kill 1 ,
349 .Xr login 1 ,
350 .Xr sh 1 ,
351 .Xr ttys 5 ,
352 .Xr security 7 ,
353 .Xr getty 8 ,
354 .Xr halt 8 ,
355 .Xr jail 8 ,
356 .Xr rc 8 ,
357 .Xr reboot 8 ,
358 .Xr shutdown 8 ,
359 .Xr sysctl 8
360 .Sh HISTORY
361 An
362 .Nm
363 utility appeared in
364 .At v6 .
365 .Sh CAVEATS
366 Systems without
367 .Xr sysctl 8
368 behave as though they have security level \-1.
369 .Pp
370 Setting the security level above 1 too early in the boot sequence can
371 prevent
372 .Xr fsck 8
373 from repairing inconsistent file systems.
374 The
375 preferred location to set the security level is at the end of
376 .Pa /etc/rc
377 after all multi-user startup actions are complete.