386BSD 0.1 development

[unix-history] / usr / src / usr.sbin / update / update.8

diff --git a/usr/src/usr.sbin/update/update.8 b/usr/src/usr.sbin/update/update.8
index 45c704c..2d0dd5b 100644 (file)
--- a/usr/src/usr.sbin/update/update.8
+++ b/usr/src/usr.sbin/update/update.8
@@ -1,39 +1,74 @@
-.\"    @(#)update.8    5.1 (Berkeley) %G%
+.\" Copyright (c) 1991 The Regents of the University of California.
+.\" All rights reserved.

 .\"
 .\"

-.TH UPDATE 8  "4 February 1983"
-.AT 3
-.SH NAME
-update \- periodically update the super block
-.SH SYNOPSIS
-.B /etc/update
-.SH DESCRIPTION
-.I Update
-is a program that executes
-the
-.IR sync (2)
-primitive every 30 seconds.
-This insures that the file system
-is fairly up to date in case of a crash.
-This command should not be executed directly,
-but should be executed out of the
-initialization shell command file.
-.SH "SEE ALSO"
-sync(2), sync(8), init(8), rc(8)
-.SH BUGS
-With
-.I update
-running,
-if the CPU is
-halted just as
-the
-.I sync
-is executed,
-a file system can be damaged.
-This is partially due to DEC hardware that
-writes zeros when NPR requests fail.
-A fix would be to have
-.IR sync (8)
-temporarily increment the system time by at
-least 30 seconds to trigger the execution of
-.I update.
-This would give 30 seconds grace to halt the CPU.
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\" 3. All advertising materials mentioning features or use of this software
+.\"    must display the following acknowledgement:
+.\"    This product includes software developed by the University of
+.\"    California, Berkeley and its contributors.
+.\" 4. Neither the name of the University nor the names of its contributors
+.\"    may be used to endorse or promote products derived from this software
+.\"    without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\"    @(#)update.8    6.5 (Berkeley) 8/5/91
+.\"
+.Dd August 5, 1991
+.Dt UPDATE 8
+.Os
+.Sh NAME
+.Nm update
+.Nd flush internal filesystem caches to disk frequently
+.Sh SYNOPSIS
+.Nm update
+.Sh DESCRIPTION
+The
+.Nm update
+command helps protect the integrity of disk volumes
+by flushing
+voliatile cached filesystem data
+to disk at thirty second intervals.
+.Nm Update
+uses the
+.Xr sync 2
+function call to do the task.
+.Pp
+.Nm Update
+is commonly invoked at startup time by
+.Xr rc 8
+when the system goes multi-user.
+.Sh SEE ALSO
+.Xr sync 2 ,
+.Xr fsck 8 ,
+.Xr init 8 ,
+.Xr rc 8 ,
+.Xr sync 8
+.Sh BUGS
+It is possible on some systems, that a
+.Xr syn
+occuring simultaneously with a crash may cause
+file system damage. See
+.Xr fsck 8 .
+.Sh HISTORY
+An
+.Nm update
+command appeared in
+.At v6 .