808a36ef65
This will make a number of things easier in the future, as well as (finally!) avoiding the Id-smashing problem which has plagued developers for so long. Boy, I'm glad we're not using sup anymore. This update would have been insane otherwise.
303 lines
8.4 KiB
Groff
303 lines
8.4 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" Donn Seeley at Berkeley Software Design, Inc.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)init.8 8.3 (Berkeley) 4/18/94
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.\" $FreeBSD$
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.\"
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.Dd April 18, 1994
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.Dt INIT 8
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.Os BSD 4
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.Sh NAME
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.Nm init
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.Nd process control initialization
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.Sh SYNOPSIS
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.Nm init
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.Sh DESCRIPTION
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The
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.Nm init
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program
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is the last stage of the boot process.
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It normally runs the automatic reboot sequence as described in
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.Xr reboot 8 ,
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and if this succeeds, begins multi-user operation.
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If the reboot scripts fail,
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.Nm init
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commences single user operation by giving
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the super-user a shell on the console.
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The
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.Nm init
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program may be passed parameters
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from the boot program to
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prevent the system from going multi-user and to instead execute
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a single user shell without starting the normal daemons.
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The system is then quiescent for maintenance work and may
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later be made to go to multi-user by exiting the
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single-user shell (with ^D).
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This
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causes
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.Nm init
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to run the
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.Pa /etc/rc
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start up command file in fastboot mode (skipping disk checks).
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.Pp
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If the
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.Nm console
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entry in the
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.Xr ttys 5
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file is marked ``insecure'',
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then
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.Nm init
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will require that the superuser password be
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entered before the system will start a single-user shell.
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The password check is skipped if the
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.Nm console
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is marked as ``secure''.
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.Pp
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The kernel runs with four different levels of security.
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Any superuser process can raise the security level, but only
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.Nm init
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can lower it.
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The security levels are:
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.Bl -tag -width flag
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.It Ic -1
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Permanently insecure mode \- always run the system in level 0 mode.
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.It Ic 0
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Insecure mode \- immutable and append-only flags may be turned off.
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All devices may be read or written subject to their permissions.
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.It Ic 1
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Secure mode \- immutable and append-only flags may not be changed;
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disks for mounted filesystems,
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.Pa /dev/mem ,
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and
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.Pa /dev/kmem
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may not be opened for writing.
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.It Ic 2
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Highly secure mode \- same as secure mode, plus disks may not be
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opened for writing (except by
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.Xr mount 2 )
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whether mounted or not.
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This level precludes tampering with filesystems by unmounting them,
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but also inhibits running
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.Xr newfs 8
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while the system is multi-user.
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.El
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.Pp
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If the security level is initially -1, then
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.Nm init
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leaves it unchanged.
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Otherwise,
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.Nm init
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arranges to run the system in level 0 mode while single user
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and in level 1 mode while multiuser.
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If level 2 mode is desired while running multiuser,
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it can be set while single user, e.g., in the startup script
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.Pa /etc/rc ,
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using
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.Xr sysctl 8 .
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.Pp
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In multi-user operation,
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.Nm init
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maintains
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processes for the terminal ports found in the file
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.Xr ttys 5 .
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.Nm Init
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reads this file, and executes the command found in the second field.
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This command is usually
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.Xr getty 8 ;
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.Nm getty
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opens and initializes the tty line
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and
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executes the
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.Xr login 1
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program.
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The
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.Nm login
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program, when a valid user logs in,
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executes a shell for that user. When this shell
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dies, either because the user logged out
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or an abnormal termination occurred (a signal),
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the
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.Nm init
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program wakes up, deletes the user
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from the
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.Xr utmp 5
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file of current users and records the logout in the
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.Xr wtmp 5
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file.
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The cycle is
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then restarted by
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.Nm init
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executing a new
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.Nm getty
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for the line.
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.Pp
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Line status (on, off, secure, getty, or window information)
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may be changed in the
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.Xr ttys 5
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file without a reboot by sending the signal
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.Dv SIGHUP
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to
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.Nm init
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with the command
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.Dq Li "kill -HUP 1" .
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On receipt of this signal,
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.Nm init
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re-reads the
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.Xr ttys 5
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file.
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When a line is turned off in
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.Xr ttys 5 ,
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.Nm init
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will send a SIGHUP signal to the controlling process
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for the session associated with the line.
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For any lines that were previously turned off in the
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.Xr ttys 5
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file and are now on,
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.Nm init
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executes a new
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.Nm getty
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to enable a new login.
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If the getty or window field for a line is changed,
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the change takes effect at the end of the current
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login session (e.g., the next time
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.Nm init
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starts a process on the line).
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If a line is commented out or deleted from
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.Xr ttys 5 ,
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.Nm init
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will not do anything at all to that line.
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However, it will complain that the relationship between lines
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in the
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.Xr ttys 5
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file and records in the
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.Xr utmp 5
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file is out of sync,
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so this practice is not recommended.
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.Pp
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.Nm Init
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will terminate multi-user operations and resume single-user mode
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if sent a terminate
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.Pq Dv TERM
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signal, for example,
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.Dq Li "kill \-TERM 1" .
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If there are processes outstanding that are deadlocked (because of
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hardware or software failure),
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.Nm init
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will not wait for them all to die (which might take forever), but
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will time out after 30 seconds and print a warning message.
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.Pp
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.Nm Init
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will cease creating new
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.Nm getty Ns 's
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and allow the system to slowly die away, if it is sent a terminal stop
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.Pq Dv TSTP
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signal, i.e.
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.Dq Li "kill \-TSTP 1" .
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A later hangup will resume full
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multi-user operations, or a terminate will start a single user shell.
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This hook is used by
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.Xr reboot 8
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and
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.Xr halt 8 .
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.Pp
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.Nm Init
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will terminate all possible processes (again, it will not wait
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for deadlocked processes) and reboot the machine if sent the interrupt
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.Pq Dv INT
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signal, i.e.
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.Dq Li "kill \-INT 1".
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This is useful for shutting the machine down cleanly from inside the kernel
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or from X when the machines appears to be hung.
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.Pp
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The role of
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.Nm init
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is so critical that if it dies, the system will reboot itself
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automatically.
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If, at bootstrap time, the
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.Nm init
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process cannot be located, the system will panic with the message
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``panic: "init died (signal %d, exit %d)''.
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.Sh DIAGNOSTICS
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.Bl -diag
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.It "getty repeating too quickly on port %s, sleeping"
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A process being started to service a line is exiting quickly
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each time it is started.
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This is often caused by a ringing or noisy terminal line.
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.Em "Init will sleep for 10 seconds" ,
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.Em "then continue trying to start the process" .
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.Pp
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.It "some processes would not die; ps axl advised."
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A process
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is hung and could not be killed when the system was shutting down.
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This condition is usually caused by a process
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that is stuck in a device driver because of
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a persistent device error condition.
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.El
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.Sh FILES
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.Bl -tag -width /var/log/wtmp -compact
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.It Pa /dev/console
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System console device.
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.It Pa /dev/tty*
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Terminal ports found in
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.Xr ttys 5 .
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.It Pa /var/run/utmp
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Record of Current users on the system.
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.It Pa /var/log/wtmp
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Record of all logins and logouts.
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.It Pa /etc/ttys
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The terminal initialization information file.
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.It Pa /etc/rc
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System startup commands.
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.El
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.Sh SEE ALSO
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.Xr kill 1 ,
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.Xr login 1 ,
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.Xr sh 1 ,
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.Xr ttys 5 ,
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.Xr crash 8 ,
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.Xr getty 8 ,
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.Xr halt 8 ,
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.Xr rc 8 ,
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.Xr reboot 8 ,
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.Xr shutdown 8
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.Sh HISTORY
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A
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.Nm
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command appeared in
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.At v6 .
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.Sh BUGS
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Systems without
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.Xr sysctl
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behave as though they have security level \-1.
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