1996-02-12 01:45:47 +01:00
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.\" Copyright (c) 1996
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.\" Mike Pritchard <mpp@FreeBSD.org>. All rights reserved.
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.\"
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.\" Copyright (c) 1991, 1993
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.\" The Regents of the University of California. 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 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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1997-03-07 03:50:01 +01:00
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.\" $Id$
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.\"
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1996-02-12 01:45:47 +01:00
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.Dd February 11, 1996
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.Dt UPDATE 4
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.Os FreeBSD
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.Sh NAME
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.Nm update
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1996-05-31 23:02:16 +02:00
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.Nd flush internal filesystem caches to disk periodically
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1996-02-12 01:45:47 +01:00
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.Sh SYNOPSIS
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.Nm update
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.Sh DESCRIPTION
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The
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.Nm update
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kernel process helps protect the integrity of disk volumes
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by flushing
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volatile cached filesystem data
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1996-05-31 23:02:16 +02:00
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to disk. This is done at thirty second intervals by default.
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The time period may be changed by using
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.Xr sysctl 8
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to modify the
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.Va kern.update
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variable.
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1996-02-12 20:27:32 +01:00
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The
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.Nm update
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process does the equivalent of the
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1996-02-12 01:45:47 +01:00
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.Xr sync 2
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function call to do the task.
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.Sh SEE ALSO
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.Xr sync 2 ,
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.Xr fsck 8 ,
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.Xr init 8 ,
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.Xr rc 8 ,
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1996-05-31 23:02:16 +02:00
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.Xr sync 8 ,
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.Xr sysctl 8
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1996-02-12 01:45:47 +01:00
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.Sh BUGS
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It is possible on some systems that a
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.Xr sync
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occurring simultaneously with a crash may cause
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1996-05-31 23:02:16 +02:00
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file system damage. See
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1996-02-12 01:45:47 +01:00
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.Xr fsck 8 .
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.Sh HISTORY
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An
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.Nm update
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command appeared in
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.At v6 ,
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and was usually started by /etc/rc when the system went multi-user.
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1996-02-12 20:27:32 +01:00
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A kernel initiated
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.Nm update
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process first appeared in
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.Fx 2.0 .
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