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.\" 4. Neither the name of the University nor the names of its contributors 16.\" may be used to endorse or promote products derived from this software 17.\" without specific prior written permission. 18.\" 19.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29.\" SUCH DAMAGE. 30.\" 31.\" @(#)init.8 8.3 (Berkeley) 4/18/94 32.\" $FreeBSD$ 33.\" 34.Dd April 18, 1994 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 48The 49.Nm 50utility 51is the last stage of the boot process. 52It normally runs the automatic reboot sequence as described in 53.Xr rc 8 , 54and if this succeeds, begins multi-user operation. 55If the reboot scripts fail, 56.Nm 57commences single-user operation by giving 58the super-user a shell on the console. 59The 60.Nm 61utility may be passed parameters 62from the boot program to 63prevent the system from going multi-user and to instead execute 64a single-user shell without starting the normal daemons. 65The system is then quiescent for maintenance work and may 66later be made to go to multi-user by exiting the 67single-user shell (with ^D). 68This 69causes 70.Nm 71to run the 72.Pa /etc/rc 73start up command file in fastboot mode (skipping disk checks). 74.Pp 75If the 76.Em console 77entry in the 78.Xr ttys 5 79file is marked 80.Dq insecure , 81then 82.Nm 83will require that the super-user password be 84entered before the system will start a single-user shell. 85The password check is skipped if the 86.Em console 87is marked as 88.Dq secure . 89.Pp 90The kernel runs with five different levels of security. 91Any super-user process can raise the security level, but no process 92can lower it. 93The security levels are: 94.Bl -tag -width flag 95.It Ic -1 96Permanently insecure mode \- always run the system in level 0 mode. 97This is the default initial value. 98.It Ic 0 99Insecure mode \- immutable and append-only flags may be turned off. 100All devices may be read or written subject to their permissions. 101.It Ic 1 102Secure mode \- the system immutable and system append-only flags may not 103be turned off; 104disks for mounted file systems, 105.Pa /dev/mem , 106.Pa /dev/kmem 107and 108.Pa /dev/io 109(if your platform has it) may not be opened for writing; 110kernel modules (see 111.Xr kld 4 ) 112may not be loaded or unloaded. 113.It Ic 2 114Highly secure mode \- same as secure mode, plus disks may not be 115opened for writing (except by 116.Xr mount 2 ) 117whether mounted or not. 118This level precludes tampering with file systems by unmounting them, 119but also inhibits running 120.Xr newfs 8 121while the system is multi-user. 122.Pp 123In addition, kernel time changes are restricted to less than or equal to one 124second. Attempts to change the time by more than this will log the message 125.Dq Time adjustment clamped to +1 second . 126.It Ic 3 127Network secure mode \- same as highly secure mode, plus 128IP packet filter rules (see 129.Xr ipfw 8 130and 131.Xr ipfirewall 4 ) 132cannot be changed and 133.Xr dummynet 4 134configuration cannot be adjusted. 135.El 136.Pp 137If the security level is initially nonzero, then 138.Nm 139leaves it unchanged. 140Otherwise, 141.Nm 142raises the level to 1 before going multi-user for the first time. 143Since the level cannot be reduced, it will be at least 1 for 144subsequent operation, even on return to single-user. 145If a level higher than 1 is desired while running multi-user, 146it can be set before going multi-user, e.g., by the startup script 147.Xr rc 8 , 148using 149.Xr sysctl 8 150to set the 151.Va kern.securelevel 152variable to the required security level. 153.Pp 154If 155.Nm 156is run in a jail, the security level of the 157.Dq host system 158will not be effected. 159Part of the information set up in the kernel to support a jail 160is a per-jail 161.Dq securelevel 162setting. 163This allows running a higher security level inside of a jail 164than that of the host system. 165See 166.Xr jail 8 167for more information about jails. 168.Pp 169In multi-user operation, 170.Nm 171maintains 172processes for the terminal ports found in the file 173.Xr ttys 5 . 174The 175.Nm 176utility reads this file and executes the command found in the second field, 177unless the first field refers to a device in 178.Pa /dev 179which is not configured. 180The first field is supplied as the final argument to the command. 181This command is usually 182.Xr getty 8 ; 183.Nm getty 184opens and initializes the tty line 185and 186executes the 187.Xr login 1 188program. 189The 190.Nm login 191program, when a valid user logs in, 192executes a shell for that user. When this shell 193dies, either because the user logged out 194or an abnormal termination occurred (a signal), 195the 196.Nm 197utility wakes up, deletes the user 198from the 199.Xr utmp 5 200file of current users and records the logout in the 201.Xr wtmp 5 202file. 203The cycle is 204then restarted by 205.Nm 206executing a new 207.Nm getty 208for the line. 209.Pp 210The 211.Nm 212utility can also be used to keep arbitrary daemons running, 213automatically restarting them if they die. 214In this case, the first field in the 215.Xr ttys 5 216file must not reference the path to a configured device node 217and will be passed to the daemon 218as the final argument on its command line. 219This is similar to the facility offered in the 220.At V 221.Pa /etc/inittab . 222.Pp 223Line status (on, off, secure, getty, or window information) 224may be changed in the 225.Xr ttys 5 226file without a reboot by sending the signal 227.Dv SIGHUP 228to 229.Nm 230with the command 231.Dq Li "kill -HUP 1" . 232On receipt of this signal, 233.Nm 234re-reads the 235.Xr ttys 5 236file. 237When a line is turned off in 238.Xr ttys 5 , 239.Nm 240will send a SIGHUP signal to the controlling process 241for the session associated with the line. 242For any lines that were previously turned off in the 243.Xr ttys 5 244file and are now on, 245.Nm 246executes the command specified in the second field. 247If the command or window field for a line is changed, 248the change takes effect at the end of the current 249login session (e.g., the next time 250.Nm 251starts a process on the line). 252If a line is commented out or deleted from 253.Xr ttys 5 , 254.Nm 255will not do anything at all to that line. 256However, it will complain that the relationship between lines 257in the 258.Xr ttys 5 259file and records in the 260.Xr utmp 5 261file is out of sync, 262so this practice is not recommended. 263.Pp 264The 265.Nm 266utility will terminate multi-user operations and resume single-user mode 267if sent a terminate 268.Pq Dv TERM 269signal, for example, 270.Dq Li "kill \-TERM 1" . 271If there are processes outstanding that are deadlocked (because of 272hardware or software failure), 273.Nm 274will not wait for them all to die (which might take forever), but 275will time out after 30 seconds and print a warning message. 276.Pp 277The 278.Nm 279utility will cease creating new processes 280and allow the system to slowly die away, if it is sent a terminal stop 281.Pq Dv TSTP 282signal, i.e.\& 283.Dq Li "kill \-TSTP 1" . 284A later hangup will resume full 285multi-user operations, or a terminate will start a single-user shell. 286This hook is used by 287.Xr reboot 8 288and 289.Xr halt 8 . 290.Pp 291The 292.Nm 293utility will terminate all possible processes (again, it will not wait 294for deadlocked processes) and reboot the machine if sent the interrupt 295.Pq Dv INT 296signal, i.e.\& 297.Dq Li "kill \-INT 1". 298This is useful for shutting the machine down cleanly from inside the kernel 299or from X when the machine appears to be hung. 300.Pp 301The 302.Nm 303utility will do the same, except it will halt the machine if sent 304the user defined signal 1 305.Pq Dv USR1 , 306or will halt and turn the power off (if hardware permits) if sent 307the user defined signal 2 308.Pq Dv USR2 . 309.Pp 310When shutting down the machine, 311.Nm 312will try to run the 313.Pa /etc/rc.shutdown 314script. 315This script can be used to cleanly terminate specific programs such 316as 317.Nm innd 318(the InterNetNews server). 319.Pp 320The role of 321.Nm 322is so critical that if it dies, the system will reboot itself 323automatically. 324If, at bootstrap time, the 325.Nm 326process cannot be located, the system will panic with the message 327.Dq "panic: init died (signal %d, exit %d)" . 328.Pp 329If run as a user process as shown in the second synopsis line, 330.Nm 331will emulate 332.At V 333behavior, i.e. super-user can specify the desired 334.Em run-level 335on a command line, and 336.Nm 337will signal the original 338(PID 1) 339.Nm 340as follows: 341.Bl -column Run-level SIGTERM 342.It Sy "Run-level Signal Action 343.It Cm 0 Ta Dv SIGUSR2 Ta "Halt and turn the power off" 344.It Cm 1 Ta Dv SIGTERM Ta "Go to single-user mode" 345.It Cm 6 Ta Dv SIGINT Ta "Reboot the machine" 346.It Cm c Ta Dv SIGTSTP Ta "Block further logins" 347.It Cm q Ta Dv SIGHUP Ta Rescan the 348.Xr ttys 5 349file 350.El 351.Sh DIAGNOSTICS 352.Bl -diag 353.It "getty repeating too quickly on port %s, sleeping." 354A process being started to service a line is exiting quickly 355each time it is started. 356This is often caused by a ringing or noisy terminal line. 357.Bf -emphasis 358Init will sleep for 30 seconds, 359then continue trying to start the process. 360.Ef 361.It "some processes would not die; ps axl advised." 362A process 363is hung and could not be killed when the system was shutting down. 364This condition is usually caused by a process 365that is stuck in a device driver because of 366a persistent device error condition. 367.El 368.Sh FILES 369.Bl -tag -width /etc/rc.shutdown -compact 370.It Pa /dev/console 371system console device 372.It Pa /dev/tty* 373terminal ports found in 374.Xr ttys 5 375.It Pa /var/run/utmp 376record of current users on the system 377.It Pa /var/log/wtmp 378record of all logins and logouts 379.It Pa /etc/ttys 380the terminal initialization information file 381.It Pa /etc/rc 382system startup commands 383.It Pa /etc/rc.shutdown 384system shutdown commands 385.El 386.Sh SEE ALSO 387.Xr kill 1 , 388.Xr login 1 , 389.Xr sh 1 , 390.Xr dummynet 4 , 391.Xr ipfirewall 4 , 392.Xr kld 4 , 393.Xr ttys 5 , 394.Xr crash 8 , 395.Xr getty 8 , 396.Xr halt 8 , 397.Xr ipfw 8 , 398.Xr jail 8 , 399.Xr rc 8 , 400.Xr reboot 8 , 401.Xr shutdown 8 , 402.Xr sysctl 8 403.Sh HISTORY 404An 405.Nm 406utility appeared in 407.At v6 . 408.Sh CAVEATS 409Systems without 410.Xr sysctl 8 411behave as though they have security level \-1. 412.Pp 413Setting the security level above 1 too early in the boot sequence can 414prevent 415.Xr fsck 8 416from repairing inconsistent file systems. The 417preferred location to set the security level is at the end of 418.Pa /etc/rc 419after all multi-user startup actions are complete. 420