This has the following advantages: - During boot, the BOOT_TIME record is now written right after the file systems become writable, but before users are allowed to log in. This means that they can't cause `hidden logins' by logging in right before init(8) kicks in. - The pututxline(3) function may potentially block on file locking, though this is very rare to occur. By placing it in an rc script, the user can still kill it with ^C if needed. - Most importantly: jails don't use init(8). This means that a force reboot of a system running jails will leave stale entries in the accounting database of the jails individually.
361 lines
9.5 KiB
Groff
361 lines
9.5 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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.\" 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 February 11, 2012
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.Dt INIT 8
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.Os
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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
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.Nm
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.Oo
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.Cm 0 | 1 | 6 |
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.Cm c | q
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.Oc
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.Sh DESCRIPTION
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The
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.Nm
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utility
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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 rc 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
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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
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utility 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
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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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.Em console
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entry in the
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.Xr ttys 5
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file is marked
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.Dq insecure ,
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then
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.Nm
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will require that the super-user 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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.Em console
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is marked as
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.Dq secure .
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.Pp
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If the system security level (see
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.Xr security 7 )
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is initially nonzero, then
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.Nm
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leaves it unchanged.
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Otherwise,
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.Nm
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raises the level to 1 before going multi-user for the first time.
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Since the level cannot be reduced, it will be at least 1 for
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subsequent operation, even on return to single-user.
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If a level higher than 1 is desired while running multi-user,
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it can be set before going multi-user, e.g., by the startup script
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.Xr rc 8 ,
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using
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.Xr sysctl 8
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to set the
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.Va kern.securelevel
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variable to the required security level.
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.Pp
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If
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.Nm
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is run in a jail, the security level of the
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.Dq host system
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will not be affected.
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Part of the information set up in the kernel to support a jail
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is a per-jail security level.
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This allows running a higher security level inside of a jail
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than that of the host system.
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See
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.Xr jail 8
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for more information about jails.
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.Pp
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In multi-user operation,
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.Nm
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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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The
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.Nm
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utility reads this file and executes the command found in the second field,
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unless the first field refers to a device in
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.Pa /dev
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which is not configured.
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The first field is supplied as the final argument to the command.
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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.
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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 cycle is restarted by
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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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The
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.Nm
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utility can also be used to keep arbitrary daemons running,
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automatically restarting them if they die.
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In this case, the first field in the
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.Xr ttys 5
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file must not reference the path to a configured device node
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and will be passed to the daemon
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as the final argument on its command line.
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This is similar to the facility offered in the
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.At V
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.Pa /etc/inittab .
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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
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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
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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
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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
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executes the command specified in the second field.
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If the command 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
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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
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will not do anything at all to that line.
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.Pp
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The
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.Nm
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utility 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
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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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The
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.Nm
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utility will cease creating new processes
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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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The
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.Nm
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utility 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 machine appears to be hung.
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.Pp
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The
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.Nm
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utility will do the same, except it will halt the machine if sent
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the user defined signal 1
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.Pq Dv USR1 ,
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or will halt and turn the power off (if hardware permits) if sent
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the user defined signal 2
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.Pq Dv USR2 .
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.Pp
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When shutting down the machine,
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.Nm
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will try to run the
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.Pa /etc/rc.shutdown
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script.
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This script can be used to cleanly terminate specific programs such
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as
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.Nm innd
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(the InterNetNews server).
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If this script does not terminate within 120 seconds,
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.Nm
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will terminate it.
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The timeout can be configured via the
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.Xr sysctl 8
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variable
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.Va kern.init_shutdown_timeout .
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.Pp
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The role of
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.Nm
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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
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process cannot be located, the system will panic with the message
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.Dq "panic: init died (signal %d, exit %d)" .
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.Pp
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If run as a user process as shown in the second synopsis line,
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.Nm
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will emulate
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.At V
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behavior, i.e., super-user can specify the desired
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.Em run-level
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on a command line, and
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.Nm
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will signal the original
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(PID 1)
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.Nm
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as follows:
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.Bl -column Run-level SIGTERM
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.It Sy "Run-level Signal Action
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.It Cm 0 Ta Dv SIGUSR2 Ta "Halt and turn the power off"
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.It Cm 1 Ta Dv SIGTERM Ta "Go to single-user mode"
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.It Cm 6 Ta Dv SIGINT Ta "Reboot the machine"
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.It Cm c Ta Dv SIGTSTP Ta "Block further logins"
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.It Cm q Ta Dv SIGHUP Ta Rescan the
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.Xr ttys 5
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file
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.El
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.Sh FILES
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.Bl -tag -width /etc/rc.shutdown -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/utx.active
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record of current users on the system
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.It Pa /var/log/utx.log
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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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.It Pa /etc/rc.shutdown
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system shutdown commands
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.El
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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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.Bf -emphasis
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Init will sleep for 30 seconds,
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then continue trying to start the process.
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.Ef
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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 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 security 7 ,
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.Xr getty 8 ,
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.Xr halt 8 ,
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.Xr jail 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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.Xr sysctl 8
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.Sh HISTORY
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An
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.Nm
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utility appeared in
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.At v6 .
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.Sh CAVEATS
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Systems without
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.Xr sysctl 8
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behave as though they have security level \-1.
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.Pp
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Setting the security level above 1 too early in the boot sequence can
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prevent
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.Xr fsck 8
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from repairing inconsistent file systems.
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The
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preferred location to set the security level is at the end of
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.Pa /etc/rc
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after all multi-user startup actions are complete.
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