1.\" Copyright (c) 1980, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Donn Seeley at Berkeley Software Design, Inc. 6.\" 7.\" Redistribution and use in source and binary forms, with or without 8.\" modification, are permitted provided that the following conditions 9.\" are met: 10.\" 1. Redistributions of source code must retain the above copyright 11.\" notice, this list of conditions and the following disclaimer. 12.\" 2. Redistributions in binary form must reproduce the above copyright 13.\" notice, this list of conditions and the following disclaimer in the 14.\" documentation and/or other materials provided with the distribution. 15.\" 3. All advertising materials mentioning features or use of this software 16.\" must display the following acknowledgement: 17.\" This product includes software developed by the University of 18.\" California, Berkeley and its contributors. 19.\" 4. Neither the name of the University nor the names of its contributors 20.\" may be used to endorse or promote products derived from this software 21.\" without specific prior written permission. 22.\" 23.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33.\" SUCH DAMAGE. 34.\" 35.\" @(#)init.8 8.3 (Berkeley) 4/18/94 36.\" $Id: init.8,v 1.8 1997/02/22 14:32:34 peter Exp $ 37.\" 38.Dd April 18, 1994 39.Dt INIT 8 40.Os BSD 4 41.Sh NAME 42.Nm init 43.Nd process control initialization 44.Sh SYNOPSIS 45.Nm init 46.Sh DESCRIPTION 47The 48.Nm init 49program 50is the last stage of the boot process. 51It normally runs the automatic reboot sequence as described in 52.Xr reboot 8 , 53and if this succeeds, begins multi-user operation. 54If the reboot scripts fail, 55.Nm init 56commences single user operation by giving 57the super-user a shell on the console. 58The 59.Nm init 60program may be passed parameters 61from the boot program to 62prevent the system from going multi-user and to instead execute 63a single user shell without starting the normal daemons. 64The system is then quiescent for maintenance work and may 65later be made to go to multi-user by exiting the 66single-user shell (with ^D). 67This 68causes 69.Nm init 70to run the 71.Pa /etc/rc 72start up command file in fastboot mode (skipping disk checks). 73.Pp 74If the 75.Nm console 76entry in the 77.Xr ttys 5 78file is marked ``insecure'', 79then 80.Nm init 81will require that the superuser password be 82entered before the system will start a single-user shell. 83The password check is skipped if the 84.Nm console 85is marked as ``secure''. 86.Pp 87The kernel runs with four different levels of security. 88Any superuser process can raise the security level, but only 89.Nm init 90can lower it. 91The security levels are: 92.Bl -tag -width flag 93.It Ic -1 94Permanently insecure mode \- always run the system in level 0 mode. 95.It Ic 0 96Insecure mode \- immutable and append-only flags may be turned off. 97All devices may be read or written subject to their permissions. 98.It Ic 1 99Secure mode \- the system immutable and system append-only flags may not 100be turned off; 101disks for mounted filesystems, 102.Pa /dev/mem , 103and 104.Pa /dev/kmem 105may not be opened for writing. 106.It Ic 2 107Highly secure mode \- same as secure mode, plus disks may not be 108opened for writing (except by 109.Xr mount 2 ) 110whether mounted or not. 111This level precludes tampering with filesystems by unmounting them, 112but also inhibits running 113.Xr newfs 8 114while the system is multi-user. 115.El 116.Pp 117If the security level is initially -1, then 118.Nm init 119leaves it unchanged. 120Otherwise, 121.Nm init 122arranges to run the system in level 0 mode while single user 123and in level 1 mode while multiuser. 124If level 2 mode is desired while running multiuser, 125it can be set while single user, e.g., in the startup script 126.Pa /etc/rc , 127using 128.Xr sysctl 8 . 129.Pp 130In multi-user operation, 131.Nm init 132maintains 133processes for the terminal ports found in the file 134.Xr ttys 5 . 135.Nm Init 136reads this file, and executes the command found in the second field. 137This command is usually 138.Xr getty 8 ; 139.Nm getty 140opens and initializes the tty line 141and 142executes the 143.Xr login 1 144program. 145The 146.Nm login 147program, when a valid user logs in, 148executes a shell for that user. When this shell 149dies, either because the user logged out 150or an abnormal termination occurred (a signal), 151the 152.Nm init 153program wakes up, deletes the user 154from the 155.Xr utmp 5 156file of current users and records the logout in the 157.Xr wtmp 5 158file. 159The cycle is 160then restarted by 161.Nm init 162executing a new 163.Nm getty 164for the line. 165.Pp 166Line status (on, off, secure, getty, or window information) 167may be changed in the 168.Xr ttys 5 169file without a reboot by sending the signal 170.Dv SIGHUP 171to 172.Nm init 173with the command 174.Dq Li "kill -HUP 1" . 175On receipt of this signal, 176.Nm init 177re-reads the 178.Xr ttys 5 179file. 180When a line is turned off in 181.Xr ttys 5 , 182.Nm init 183will send a SIGHUP signal to the controlling process 184for the session associated with the line. 185For any lines that were previously turned off in the 186.Xr ttys 5 187file and are now on, 188.Nm init 189executes a new 190.Nm getty 191to enable a new login. 192If the getty or window field for a line is changed, 193the change takes effect at the end of the current 194login session (e.g., the next time 195.Nm init 196starts a process on the line). 197If a line is commented out or deleted from 198.Xr ttys 5 , 199.Nm init 200will not do anything at all to that line. 201However, it will complain that the relationship between lines 202in the 203.Xr ttys 5 204file and records in the 205.Xr utmp 5 206file is out of sync, 207so this practice is not recommended. 208.Pp 209.Nm Init 210will terminate multi-user operations and resume single-user mode 211if sent a terminate 212.Pq Dv TERM 213signal, for example, 214.Dq Li "kill \-TERM 1" . 215If there are processes outstanding that are deadlocked (because of 216hardware or software failure), 217.Nm init 218will not wait for them all to die (which might take forever), but 219will time out after 30 seconds and print a warning message. 220.Pp 221.Nm Init 222will cease creating new 223.Nm getty Ns 's 224and allow the system to slowly die away, if it is sent a terminal stop 225.Pq Dv TSTP 226signal, i.e. 227.Dq Li "kill \-TSTP 1" . 228A later hangup will resume full 229multi-user operations, or a terminate will start a single user shell. 230This hook is used by 231.Xr reboot 8 232and 233.Xr halt 8 . 234.Pp 235.Nm Init 236will terminate all possible processes (again, it will not wait 237for deadlocked processes) and reboot the machine if sent the interrupt 238.Pq Dv INT 239signal, i.e. 240.Dq Li "kill \-INT 1". 241This is useful for shutting the machine down cleanly from inside the kernel 242or from X when the machine appears to be hung. 243.Pp 244The role of 245.Nm init 246is so critical that if it dies, the system will reboot itself 247automatically. 248If, at bootstrap time, the 249.Nm init 250process cannot be located, the system will panic with the message 251``panic: "init died (signal %d, exit %d)''. 252.Sh DIAGNOSTICS 253.Bl -diag 254.It "getty repeating too quickly on port %s, sleeping" 255A process being started to service a line is exiting quickly 256each time it is started. 257This is often caused by a ringing or noisy terminal line. 258.Em "Init will sleep for 10 seconds" , 259.Em "then continue trying to start the process" . 260.Pp 261.It "some processes would not die; ps axl advised." 262A process 263is hung and could not be killed when the system was shutting down. 264This condition is usually caused by a process 265that is stuck in a device driver because of 266a persistent device error condition. 267.El 268.Sh FILES 269.Bl -tag -width /var/log/wtmp -compact 270.It Pa /dev/console 271System console device. 272.It Pa /dev/tty* 273Terminal ports found in 274.Xr ttys 5 . 275.It Pa /var/run/utmp 276Record of Current users on the system. 277.It Pa /var/log/wtmp 278Record of all logins and logouts. 279.It Pa /etc/ttys 280The terminal initialization information file. 281.It Pa /etc/rc 282System startup commands. 283.El 284.Sh SEE ALSO 285.Xr kill 1 , 286.Xr login 1 , 287.Xr sh 1 , 288.Xr ttys 5 , 289.Xr crash 8 , 290.Xr getty 8 , 291.Xr halt 8 , 292.Xr rc 8 , 293.Xr reboot 8 , 294.Xr shutdown 8 295.Sh HISTORY 296A 297.Nm 298command appeared in 299.At v6 . 300.Sh BUGS 301Systems without 302.Xr sysctl 303behave as though they have security level \-1. 304