The conclusion drawn from the replies I got was that my fears of
filesystem disasters were unfounded. There are SOME issues to be aware
of, but otherwise setting back the clock is workable. I have appended
all the replies I recieved and my original question.
Marc S. Gibian
Telos Consulting Services phone: (617) 377-6350
PRISM/TFS email: gibian@stars1.hanscom.af.mil
------------ original -----------------------------------
My customer has an application that includes an aging mechanism in its
database. They are about to ship out a system that will need to be
able to operate with solely the database contents it holds when it
gets unplugged from the network here. The time period involved,
though, would normally cause the aging mechanism to purge too much of
that data.
The customer would like to be able to set the date/time at boot time
on the machine to the date/time that we disconnect it from the network
here. My experience with Unix has always been that this is a bad thing
to do, that the Unix filesystems use the date/time for generating
identifiers (uid-s?) that must be unique and that setting back the
clock causes potential collisions that are not accounted for in the
OS. Is this true?
Is it okay to force the date/time back to a given time at boot time?
What are the risks involved?
----------------------------------------------------------
>From sweh@mpn.com Sun Jan 21 06:04:05 1996
From: sweh@mpn.com (Stephen Harris)
Subject: Re: URGENT: setting back the date on SunOS 4.1.3
To: gibian@typhoon.HANSCOM.AF.MIL
Date: Sun, 21 Jan 1996 11:02:45 +0000 (GMT)
In-Reply-To: <9601191948.AA12988@typhoon.forecast> from "Marc Gibian" at Jan 19, 96 02:48:07 pm
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> Is it okay to force the date/time back to a given time at boot time?
Should be..
> What are the risks involved?
Anything time based - eg cron/at, or timestamp based - eg Make could get
confused.
rgds
Stephen
-----------------------------------------------------------------------------
>From heas@nexen.com Sun Jan 21 12:05:17 1996
Date: Sun, 21 Jan 1996 12:04:24 -0500
From: "Heas H. Heas" <heas@nexen.com>
To: gibian@typhoon.HANSCOM.AF.MIL
Subject: Re: URGENT: setting back the date on SunOS 4.1.3
Content-Length: 1378
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> From sun-managers-relay@ra.mcs.anl.gov Sun Jan 21 02:21:43 1996
>
> My customer has an application that includes an aging mechanism in its
> database. They are about to ship out a system that will need to be
> able to operate with solely the database contents it holds when it
> gets unplugged from the network here. The time period involved,
> though, would normally cause the aging mechanism to purge too much of
> that data.
>
> The customer would like to be able to set the date/time at boot time
> on the machine to the date/time that we disconnect it from the network
> here. My experience with Unix has always been that this is a bad thing
> to do, that the Unix filesystems use the date/time for generating
> identifiers (uid-s?) that must be unique and that setting back the
> clock causes potential collisions that are not accounted for in the
> OS. Is this true?
>
> Is it okay to force the date/time back to a given time at boot time?
>
> What are the risks involved?
>
> Thanks everyone for your help,
> Marc
>
> Marc S. Gibian
> Telos Consulting Services phone: (617) 377-6350
> PRISM/TFS email: gibian@stars1.hanscom.af.mil
you could create ("replace") the gettimeofday function with one
that _always_ returns the same date....and link your program with that
lib...or set LD_LIBRARY_PATH and use a dynamically loaded lib.
-heas
-----------------------------------------------------------------------------
>From eshafto@caxy.lfa.lfc.edu Mon Jan 22 10:24:47 1996
Date: Mon, 22 Jan 1996 08:36:51 -0600 (CST)
From: Eric Shafto <eshafto@caxy.lfa.lfc.edu>
Subject: Re: URGENT: setting back the date on SunOS 4.1.3
In-Reply-To: <9601191948.AA12988@typhoon.forecast>
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To: Marc Gibian <gibian@typhoon.HANSCOM.AF.MIL>
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If the machine is turned off at 2/1/96 at 12:00, and the next time you
start it up you set it to 2/1/96 at 13:00, I don't see where there's any
potential for conflict.
Eric Shafto
Dir. Academic Computing, Lake Forest Academy
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