🚀 go-pugleaf

From: Christopher C. Stacy <CSTACY@MIT-MC.ARPA>

    Date: Tue, 20 Aug 85 13:39 EDT
    From: David C. Plummer in disguise <DCP at SCRC-QUABBIN.ARPA>
    To:   Christopher C. Stacy <CSTACY at MIT-MC.ARPA>,
          jsq%tzec.UTEXAS at UT-SALLY.ARPA
    cc:   TCP-IP at SRI-NIC.ARPA
    Re:   voting on the time
    In-Reply-To: <[MIT-MC.ARPA].618951.850820.CSTACY>

        Date: Tue, 20 Aug 85 12:19:13 EDT
        From: Christopher C. Stacy <CSTACY@MIT-MC.ARPA>

        When voting on the time, another piece of information which almost
        everyone has at their disposal is the reference date of certain files
        which must be accessed when the system is run.  This can be used as an
        error check against the propogation of bad times (which has happenned
        occasionally on our local network). Network (or other) times preceeding
        the file date are probably bogus.

    But what happens if somebody spazzes and warps MIT-MC 9 months into the
    future.  (It has happened before.)  What if one of the files you check
    against was created by such a time-warped machine?  Indeed, the normal
    case will be caught by your probable-bogosity meter, but when the
    baseline is bogus, then what?  

Yeah, that's a pretty awful state to get into.  Part of the
recovery strategy for a file system which was active with
the wrong time should be to locate (important) files which
may have been written with the wrong date and fix them to
sometime in the past, perhaps the shutdown time.

The file date hack is not intended as a recovery mechanism
for bad times.  It is merely another source of information
that tells you when things appear inconsistant.  Some human
who knows better can come along and consult a sundial or
something to decide which time is really correct.

Also, the file date check is only useful for fairly gross
times.  It might be appropriate to use it when booting the
system to see if tomorrow is yesterday, but I wouldn't
bother trying to use it for second (or minute) accuracy.

    What about systems who can't access the filesystem until the time 
    is known?

That's what "almost everyone" in my statement refers to. You obviously
can't use this hack if you can't read the file directory information.