4035c9100d
Obtained from NetBSD and then modified to reflect how things work in FreeBSD, along with some minor changes to make a few points clearer.
120 lines
3.9 KiB
Groff
120 lines
3.9 KiB
Groff
.\" $NetBSD: inittodr.9,v 1.2 1996/03/27 21:16:06 jtc Exp $
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.\"
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.\" Copyright (c) 1994 Christopher G. Demetriou
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.\" All rights reserved.
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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 Christopher G. Demetriou
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.\" for the NetBSD Project.
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.\" 3. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.Dd March 22, 1997
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.Dt INITTODR 9
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.Os FreeBSD
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.Sh NAME
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.Nm inittodr
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.Nd initialize system time
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.Sh SYNOPSIS
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.Ft void
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.Fn inittodr "time_t base"
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.Sh DESCRIPTION
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The
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.Fn inittodr
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function determines the time and sets the system clock.
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It tries to pick the correct time using a set of heuristics that examine
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the system's battery backed clock and the time obtained from the root
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file system, as given in
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.Fa base .
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How the
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.Fa base
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value is obtained will vary depending on the
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root file system type.
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The heuristics used include:
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.Bl -bullet
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.It
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If the battery-backed clock has a valid time, it is used.
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.\" .It
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.\" If the battery-backed clock does not have a valid time, and
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.\" the time provided in
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.\" .Fa base
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.\" is within reason,
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.\" .Fa base
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.\" is used as the current time.
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.\" .It
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.\" If the battery-backed clock appears invalid, and
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.\" .Fa base
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.\" appears non-sensical or was not provided (was given as zero),
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.\" a arbitrary base (typically some time in the late 1970s)
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.\" will be used.
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.It
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If the battery-backed clock does not have a valid time,
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the time provided in
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.Fa base
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will be used.
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.El
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.Pp
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Once a system time has been determined, it is stored in the
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.Va time
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variable.
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.Sh DIAGNOSTICS
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The
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.Fn inittodr
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function prints diagnostic messages if it has trouble figuring
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out the system time. Conditions that can cause diagnostic
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messages to be printed include:
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.Bl -bullet
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.It
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The battery-backed clock's time appears nonsensical.
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.\" .It
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.\" The
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.\" .Fa base
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.\" time appears nonsensical.
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.\" .It
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.\" The
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.\" .Fa base
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.\" time and the battery-backed clock's time differ by a large amount.
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.El
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.Sh SEE ALSO
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.Xr resettodr 9 ,
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.Xr time 9
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.Sh BUGS
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On many systems,
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.Fn inittodr
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has to convert from
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a time expressed in terms of year, month, day, hours, minutes,
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and seconds to
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.Va time ,
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expressed in seconds. Many of the implementations could share code,
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but do not.
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.Pp
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Each system's heuristics for picking the correct time are slightly
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different.
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.Pp
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The
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.Tn FreeBSD
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implementation should do a better job of validating the time provided in
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.Fa base
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when the battery-backed clock is unusable. Currently it unconditionally
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sets the system clock to this value.
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