361 lines
9.8 KiB
Groff
361 lines
9.8 KiB
Groff
.\" $NetBSD: init.8,v 1.23 2001/06/05 11:22:45 wiz Exp $
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.\"
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.\" 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 8.6 (Berkeley) 5/26/95
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.\"
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.Dd April 29, 2000
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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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.Sh DESCRIPTION
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The
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.Nm
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program is the last stage of the boot process (after the kernel loads
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and initializes all the devices).
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It normally begins multi-user operation.
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.Pp
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The following table describes the state machine used by
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.Nm "" :
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.Bl -enum
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.It
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Single user shell.
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.Nm
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may be passed
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.Fl s
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from the boot program to prevent the system from going multi-user and
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to instead execute a single user shell without starting the normal
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daemons. The system is then quiescent for maintenance work and may
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later be made to go to state 2 (multi-user) by exiting the single-user
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shell (with ^D).
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.It
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Multi-user boot (default operation).
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Executes
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.Pa /etc/rc
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(see
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.Xr rc 8 ) .
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If this was the first state entered (as opposed to entering here after
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state 1), then
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.Pa /etc/rc
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will be invoked with its first argument being
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.Sq autoboot .
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If
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.Pa /etc/rc
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exits with a non-zero (error) exit code, commence single user
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operation by giving the super-user a shell on the console by going
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to state 1 (single user).
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Otherwise, proceed to state 3.
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.It
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Setup ttys as specified in
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.Xr ttys 5 .
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See below for more information.
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On completion, continue to state 4.
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.It
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Multi-user operation.
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Depending upon the signal received, change state appropriately;
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on
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.Dv SIGTERM ,
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go to state 7;
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on
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.Dv SIGHUP ,
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go to state 5;
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on
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.Dv SIGTSTP ,
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go to state 6.
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.It
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Clean-up mode; re-read
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.Xr ttys 5 ,
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killing off the controlling processes on lines that are now
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.Sq off ,
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and starting processes that are newly
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.Sq on .
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On completion, go to state 4.
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.It
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.Sq Boring
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mode; no new sessions.
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Signals as per state 4.
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.It
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Shutdown mode.
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Send
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.Dv SIGHUP
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to all controlling processes, reap the processes for 30 seconds,
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and the go to state 1 (single user); warning if not all the processes died.
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.El
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.Pp
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If the
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.Sq console
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entry in the
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.Xr ttys 5
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file is marked ``insecure'', then
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.Nm
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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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.Sq 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
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can lower it.
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Security levels are defined as follows:
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.Bl -tag -width flag
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.It Ic -1
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Permanently insecure mode \- always run 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 changed.
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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 \- system immutable and system append-only flags may not
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be turned off; 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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are read-only.
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.It Ic 2
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Highly secure mode \- same as secure mode, plus disks are always
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read-only whether mounted or not, new disks may not be mounted,
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and existing mounts may only be downgraded from read-write to read-only.
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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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.Pp
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The
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.Xr settimeofday 2
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system call can only advance the time.
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.Pp
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The state of
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.Xr ipf 8
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(the in-kernel IP filtering facility) may not be changed.
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.Pp
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Users may not change the per-process core name template format, only the
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default can be changed.
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.Pp
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Downgrading from highly secure mode to insecure mode (that is, to single-user
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mode) always requires the root password to be entered on the console, whether
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the console is marked as 'secure' in
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.Pa /etc/ttys
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or not.
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.El
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.Pp
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Normally, the system runs in level 0 mode while single user
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and in level 1 mode while multi-user.
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If the level 2 mode is desired while running multi-user,
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it can be set 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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If it is desired to run the system in level 0 mode while multi-user,
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the administrator must build a kernel with
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.Sy options INSECURE
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in the kernel configuration file, which initializes the kernel's
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.Va securelevel
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variable to -1.
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See
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.Xr options 4
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and
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.Xr config 8
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for details.
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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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.Nm
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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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it opens and initializes the tty line and executes the
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.Xr login 1
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program.
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The
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.Xr login 1
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program, when a valid user logs in, executes a shell for that user.
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When this shell dies, either because the user logged out or an
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abnormal termination occurred (a signal), the
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.Nm
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program wakes up, deletes the user 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
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executing a new
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.Xr getty 8
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for the line.
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.pl +1
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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 \-s HUP 1" .
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This is referenced in the table above as state 5.
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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
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.Dv SIGHUP
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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 a new
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.Xr getty 8
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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
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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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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
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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 \-s 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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.Nm
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will cease creating new
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.Xr getty 8 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 \-s 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 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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``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 login 1 ,
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.Xr kill 1 ,
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.Xr sh 1 ,
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.Xr options 4 ,
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.Xr ttys 5 ,
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.Xr config 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 8
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behave as though they have security level \-1.
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