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35 .\" @(#)init.8 8.3 (Berkeley) 4/18/94
43 .Nd process control initialization
55 is the last stage of the boot process.
56 It normally runs the automatic reboot sequence as described in
58 and if this succeeds, begins multi-user operation.
59 If the reboot scripts fail,
61 commences single-user operation by giving
62 the super-user a shell on the console.
65 program may be passed parameters
66 from the boot program to
67 prevent the system from going multi-user and to instead execute
68 a single-user shell without starting the normal daemons.
69 The system is then quiescent for maintenance work and may
70 later be made to go to multi-user by exiting the
71 single-user shell (with ^D).
77 start up command file in fastboot mode (skipping disk checks).
87 will require that the super-user password be
88 entered before the system will start a single-user shell.
89 The password check is skipped if the
94 The kernel runs with four different levels of security.
95 Any super-user process can raise the security level, but no process
97 The security levels are:
100 Permanently insecure mode \- always run the system in level 0 mode.
101 This is the default initial value.
103 Insecure mode \- immutable and append-only flags may be turned off.
104 All devices may be read or written subject to their permissions.
106 Secure mode \- the system immutable and system append-only flags may not
108 disks for mounted filesystems,
112 may not be opened for writing.
114 Highly secure mode \- same as secure mode, plus disks may not be
115 opened for writing (except by
117 whether mounted or not.
118 This level precludes tampering with filesystems by unmounting them,
119 but also inhibits running
121 while the system is multi-user.
123 In addition, kernel time changes are restricted to less than or equal to one
124 second. Attempts to change the time by more than this will log the message
125 .Dq Time adjustment clamped to +1 second .
127 Network secure mode \- same as highly secure mode, plus
128 IP packet filter rules (see
132 cannot be changed and
134 configuration cannot be adjusted.
137 If the security level is initially -1, then
142 arranges to run the system in level 0 mode while single-user
143 and in level 1 mode while multi-user.
144 If level 2 mode is desired while running multi-user,
145 it can be set while single-user, e.g., in the startup script
151 variable to the required security level.
153 In multi-user operation,
156 processes for the terminal ports found in the file
159 reads this file and executes the command found in the second field,
160 unless the first field refers to a device in
162 which is not configured.
163 The first field is supplied as the final argument to the command.
164 This command is usually
167 opens and initializes the tty line
174 program, when a valid user logs in,
175 executes a shell for that user. When this shell
176 dies, either because the user logged out
177 or an abnormal termination occurred (a signal),
180 program wakes up, deletes the user
183 file of current users and records the logout in the
194 can also be used to keep arbitrary daemons running,
195 automatically restarting them if they die.
196 In this case, the first field in the
198 file must not reference the path to a configured device node
199 and will be passed to the daemon
200 as the final argument on its command line.
201 This is similar to the facility offered in the
205 Line status (on, off, secure, getty, or window information)
206 may be changed in the
208 file without a reboot by sending the signal
213 .Dq Li "kill -HUP 1" .
214 On receipt of this signal,
219 When a line is turned off in
222 will send a SIGHUP signal to the controlling process
223 for the session associated with the line.
224 For any lines that were previously turned off in the
228 executes the command specified in the second field.
229 If the command or window field for a line is changed,
230 the change takes effect at the end of the current
231 login session (e.g., the next time
233 starts a process on the line).
234 If a line is commented out or deleted from
237 will not do anything at all to that line.
238 However, it will complain that the relationship between lines
241 file and records in the
244 so this practice is not recommended.
247 will terminate multi-user operations and resume single-user mode
251 .Dq Li "kill \-TERM 1" .
252 If there are processes outstanding that are deadlocked (because of
253 hardware or software failure),
255 will not wait for them all to die (which might take forever), but
256 will time out after 30 seconds and print a warning message.
259 will cease creating new processes
260 and allow the system to slowly die away, if it is sent a terminal stop
263 .Dq Li "kill \-TSTP 1" .
264 A later hangup will resume full
265 multi-user operations, or a terminate will start a single-user shell.
272 will terminate all possible processes (again, it will not wait
273 for deadlocked processes) and reboot the machine if sent the interrupt
276 .Dq Li "kill \-INT 1".
277 This is useful for shutting the machine down cleanly from inside the kernel
278 or from X when the machine appears to be hung.
281 will do the same, except it will halt the machine if sent
282 the user defined signal 1
284 or will halt and turn the power off (if hardware permits) if sent
285 the user defined signal 2
288 When shutting down the machine,
292 script. This script can be used to cleanly terminate specific programs such
295 (the InterNetNews server).
299 is so critical that if it dies, the system will reboot itself
301 If, at bootstrap time, the
303 process cannot be located, the system will panic with the message
304 .Dq "panic: init died (signal %d, exit %d)" .
306 If run as a user process as shown in the second synopsis line,
310 behavior, i.e. super-user can specify the desired
312 on a command line, and
314 will signal the original
318 .Bl -column Run-level SIGTERM
319 .It Sy Run-level Signal Action
320 .It Cm 0 Ta Dv SIGUSR2 Ta "Halt and turn the power off"
321 .It Cm 1 Ta Dv SIGTERM Ta "Go to single-user mode"
322 .It Cm 6 Ta Dv SIGINT Ta "Reboot the machine"
323 .It Cm c Ta Dv SIGTSTP Ta "Block further logins"
324 .It Cm q Ta Dv SIGHUP Ta Rescan the
330 .It "getty repeating too quickly on port %s, sleeping"
331 A process being started to service a line is exiting quickly
332 each time it is started.
333 This is often caused by a ringing or noisy terminal line.
334 .Em "Init will sleep for 30 seconds" ,
335 .Em "then continue trying to start the process" .
337 .It "some processes would not die; ps axl advised."
339 is hung and could not be killed when the system was shutting down.
340 This condition is usually caused by a process
341 that is stuck in a device driver because of
342 a persistent device error condition.
345 .Bl -tag -width /etc/rc.shutdown -compact
347 system console device
349 terminal ports found in
352 record of current users on the system
354 record of all logins and logouts
356 the terminal initialization information file
358 system startup commands
359 .It Pa /etc/rc.shutdown
360 system shutdown commands
385 behave as though they have security level \-1.
387 Setting the security level above 1 too early in the boot sequence can
390 from repairing inconsistent filesystems. The
391 preferred location to set the security level is at the end of
393 after all multi-user startup actions are complete.