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.\" 37.Dd April 18, 1994 38.Dt INIT 8 39.Os BSD 4 40.Sh NAME 41.Nm init 42.Nd process control initialization 43.Sh SYNOPSIS 44.Nm init 45.Sh DESCRIPTION 46The 47.Nm init 48program 49is the last stage of the boot process. 50It normally runs the automatic reboot sequence as described in 51.Xr reboot 8 , 52and if this succeeds, begins multi-user operation. 53If the reboot scripts fail, 54.Nm init 55commences single user operation by giving 56the super-user a shell on the console. 57The 58.Nm init 59program may be passed parameters 60from the boot program to 61prevent the system from going multi-user and to instead execute 62a single user shell without starting the normal daemons. 63The system is then quiescent for maintenance work and may 64later be made to go to multi-user by exiting the 65single-user shell (with ^D). 66This 67causes 68.Nm init 69to run the 70.Pa /etc/rc 71start up command file in fastboot mode (skipping disk checks). 72.Pp 73If the 74.Nm console 75entry in the 76.Xr ttys 5 77file is marked ``insecure'', 78then 79.Nm init 80will require that the superuser password be 81entered before the system will start a single-user shell. 82The password check is skipped if the 83.Nm console 84is marked as ``secure''. 85.Pp 86The kernel runs with four different levels of security. 87Any superuser process can raise the security level, but only 88.Nm init 89can lower it. 90The security levels are: 91.Bl -tag -width flag 92.It Ic -1 93Permanently insecure mode \- always run the system in level 0 mode. 94.It Ic 0 95Insecure mode \- immutable and append-only flags may be turned off. 96All devices may be read or written subject to their permissions. 97.It Ic 1 98Secure mode \- immutable and append-only flags may not be changed; 99disks for mounted filesystems, 100.Pa /dev/mem , 101and 102.Pa /dev/kmem 103may not be opened for writing. 104.It Ic 2 105Highly secure mode \- same as secure mode, plus disks may not be 106opened for writing (except by 107.Xr mount 2 ) 108whether mounted or not. 109This level precludes tampering with filesystems by unmounting them, 110but also inhibits running 111.Xr newfs 8 112while the system is multi-user. 113.El 114.Pp 115If the security level is initially -1, then 116.Nm init 117leaves it unchanged. 118Otherwise, 119.Nm init 120arranges to run the system in level 0 mode while single user 121and in level 1 mode while multiuser. 122If level 2 mode is desired while running multiuser, 123it can be set while single user, e.g., in the startup script 124.Pa /etc/rc , 125using 126.Xr sysctl 8 . 127.Pp 128In multi-user operation, 129.Nm init 130maintains 131processes for the terminal ports found in the file 132.Xr ttys 5 . 133.Nm Init 134reads this file, and executes the command found in the second field. 135This command is usually 136.Xr getty 8 ; 137.Nm getty 138opens and initializes the tty line 139and 140executes the 141.Xr login 1 142program. 143The 144.Nm login 145program, when a valid user logs in, 146executes a shell for that user. When this shell 147dies, either because the user logged out 148or an abnormal termination occurred (a signal), 149the 150.Nm init 151program wakes up, deletes the user 152from the 153.Xr utmp 5 154file of current users and records the logout in the 155.Xr wtmp 5 156file. 157The cycle is 158then restarted by 159.Nm init 160executing a new 161.Nm getty 162for the line. 163.Pp 164Line status (on, off, secure, getty, or window information) 165may be changed in the 166.Xr ttys 5 167file without a reboot by sending the signal 168.Dv SIGHUP 169to 170.Nm init 171with the command 172.Dq Li "kill -HUP 1" . 173On receipt of this signal, 174.Nm init 175re-reads the 176.Xr ttys 5 177file. 178When a line is turned off in 179.Xr ttys 5 , 180.Nm init 181will send a SIGHUP signal to the controlling process 182for the session associated with the line. 183For any lines that were previously turned off in the 184.Xr ttys 5 185file and are now on, 186.Nm init 187executes a new 188.Nm getty 189to enable a new login. 190If the getty or window field for a line is changed, 191the change takes effect at the end of the current 192login session (e.g., the next time 193.Nm init 194starts a process on the line). 195If a line is commented out or deleted from 196.Xr ttys 5 , 197.Nm init 198will not do anything at all to that line. 199However, it will complain that the relationship between lines 200in the 201.Xr ttys 5 202file and records in the 203.Xr utmp 5 204file is out of sync, 205so this practice is not recommended. 206.Pp 207.Nm Init 208will terminate multi-user operations and resume single-user mode 209if sent a terminate 210.Pq Dv TERM 211signal, for example, 212.Dq Li "kill \-TERM 1" . 213If there are processes outstanding that are deadlocked (because of 214hardware or software failure), 215.Nm init 216will not wait for them all to die (which might take forever), but 217will time out after 30 seconds and print a warning message. 218.Pp 219.Nm Init 220will cease creating new 221.Nm getty Ns 's 222and allow the system to slowly die away, if it is sent a terminal stop 223.Pq Dv TSTP 224signal, i.e. 225.Dq Li "kill \-TSTP 1" . 226A later hangup will resume full 227multi-user operations, or a terminate will start a single user shell. 228This hook is used by 229.Xr reboot 8 230and 231.Xr halt 8 . 232.Pp 233.Nm Init 234will terminate all possible processes (again, it will not wait 235for deadlocked processes) and reboot the machine if sent the interrupt 236.Pq Dv INT 237signal, i.e. 238.Dq Li "kill \-INT 1". 239This is useful for shutting the machine down cleanly from inside the kernel 240or from X when the machines appears to be hung. 241.Pp 242The role of 243.Nm init 244is so critical that if it dies, the system will reboot itself 245automatically. 246If, at bootstrap time, the 247.Nm init 248process cannot be located, the system will panic with the message 249``panic: "init died (signal %d, exit %d)''. 250.Sh DIAGNOSTICS 251.Bl -diag 252.It "getty repeating too quickly on port %s, sleeping" 253A process being started to service a line is exiting quickly 254each time it is started. 255This is often caused by a ringing or noisy terminal line. 256.Em "Init will sleep for 10 seconds" , 257.Em "then continue trying to start the process" . 258.Pp 259.It "some processes would not die; ps axl advised." 260A process 261is hung and could not be killed when the system was shutting down. 262This condition is usually caused by a process 263that is stuck in a device driver because of 264a persistent device error condition. 265.El 266.Sh FILES 267.Bl -tag -width /var/log/wtmp -compact 268.It Pa /dev/console 269System console device. 270.It Pa /dev/tty* 271Terminal ports found in 272.Xr ttys 5 . 273.It Pa /var/run/utmp 274Record of Current users on the system. 275.It Pa /var/log/wtmp 276Record of all logins and logouts. 277.It Pa /etc/ttys 278The terminal initialization information file. 279.It Pa /etc/rc 280System startup commands. 281.El 282.Sh SEE ALSO 283.Xr login 1 , 284.Xr kill 1 , 285.Xr sh 1 , 286.Xr ttys 5 , 287.Xr crash 8 , 288.Xr getty 8 , 289.Xr rc 8 , 290.Xr reboot 8 , 291.Xr halt 8 , 292.Xr shutdown 8 293.Sh HISTORY 294A 295.Nm 296command appeared in 297.At v6 . 298.Sh BUGS 299Systems without 300.Xr sysctl 301behave as though they have security level \-1. 302