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	1	.\" Copyright (c) 1990, 1991, 1993
	2	.\" The Regents of the University of California. All rights reserved.
	3	.\"
	4	.\" Redistribution and use in source and binary forms, with or without
	5	.\" modification, are permitted provided that the following conditions
	6	.\" are met:
	7	.\" 1. Redistributions of source code must retain the above copyright
	8	.\" notice, this list of conditions and the following disclaimer.
	9	.\" 2. Redistributions in binary form must reproduce the above copyright
	10	.\" notice, this list of conditions and the following disclaimer in the
	11	.\" documentation and/or other materials provided with the distribution.
	12	.\" 3. All advertising materials mentioning features or use of this software
	13	.\" must display the following acknowledgement:
	14	.\" This product includes software developed by the University of
	15	.\" California, Berkeley and its contributors.
	16	.\" 4. Neither the name of the University nor the names of its contributors
	17	.\" may be used to endorse or promote products derived from this software
	18	.\" without specific prior written permission.
	19	.\"
	20	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	.\" SUCH DAMAGE.
	31	.\"
	32	.\" @(#)reboot.8 8.1 (Berkeley) 6/9/93
	33	.\" $FreeBSD: src/sbin/reboot/reboot.8,v 1.21 2002/12/27 12:15:33 schweikh Exp $
	34	.\"
	35	.Dd June 9, 1993
	36	.Dt REBOOT 8
	37	.Os
	38	.Sh NAME
	39	.Nm halt ,
	40	.Nm reboot
	41	.Nd stopping and restarting the system
	42	.Sh SYNOPSIS
	43	.Nm halt
	44	.Op Fl lnqu
	45	.Nm reboot
	46	.Op Fl lnq
	47	.Sh DESCRIPTION
	48	The
	49	.Nm halt
	50	and
	51	.Nm reboot
	52	utilities flush the file system cache to disk,
	53	send all running processes a
	54	.Dv SIGTERM
	55	(and subsequently a
	56	.Dv SIGKILL )
	57	and, respectively, halt or restart the system.
	58	The action is logged, including entering a shutdown record into the
	59	.Xr wtmp 5
	60	file.
	61	.Pp
	62	When the system is halted with the halt command, the system is powered off.
	63	.Pp
	64	The options are as follows:
	65	.Bl -tag -width indent
	66	.It Fl l
	67	The halt or reboot is
	68	.Em not
	69	recorded in the system log.
	70	This option is intended for applications such as
	71	.Xr shutdown 8 ,
	72	that call
	73	.Nm reboot
	74	or
	75	.Nm halt
	76	and log this themselves.
	77	.It Fl n
	78	The file system cache is not flushed.
	79	This option should probably not be used.
	80	.It Fl q
	81	The system is halted or restarted quickly and ungracefully, and only
	82	the flushing of the file system cache is performed (if the
	83	.Fl n
	84	option is not specified).
	85	This option should probably not be used.
	86	.It Fl u
	87	The system is halted up until the point of removing system power, but waits
	88	before removing power for 5 minutes so that an external UPS
	89	(uninterruptible power supply) can forcibly remove power.
	90	This simulates a dirty shutdown to permit a later automatic power on. OS X uses
	91	this mode automatically with supported UPSs in emergency shutdowns.
	92	.El
	93	.Pp
	94	Normally, the
	95	.Xr shutdown 8
	96	utility is used when the system needs to be halted or restarted, giving
	97	users advance warning of their impending doom and cleanly terminating
	98	specific programs.
	99	.Sh SIGTERM TO SIGKILL INTERVAL
	100	The
	101	.Dv SIGKILL
	102	will follow the
	103	.Dv SIGTERM
	104	by an intentionally indeterminate period of time.
	105	Programs are expected to take only enough time to flush all dirty data and exit.
	106	Developers are encouraged to file a bug with the OS vendor, should they encounter an issue with this functionality.
	107	.Sh SEE ALSO
	108	.Xr wtmp 5 ,
	109	.Xr shutdown 8 ,
	110	.Xr sync 8
	111	.Sh HISTORY
	112	A
	113	.Nm reboot
	114	utility appeared in
	115	.At v6 .