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Newsgroups: comp.os.linux.misc,comp.sys.raspberry-pi
Subject: Re: Keeping 'order' without RTC.
Date: Sat, 25 Apr 2015 23:09:12 +0000 (UTC)
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On Wed, 15 Apr 2015 22:37:00 +0200, Morten Reistad wrote:

> In article <j6knia997ndg4n6ufjecncb3g27cqhdb17@4ax.com>, Gordon Levi 
> <gordon@address.invalid> wrote:
>>The Natural Philosopher <tnp@invalid.invalid> wrote:
>>
>>>On 13/04/15 14:14, Joe Beanfish wrote:
>>>
>>>
>>>> Please, just butt out of you have nothing to offer. You're worse than
>>>> the so-called troll. Same for the rest of ya, there's more blather by
>>>> you folk whining or being super-superior about the "troll" than
>>>> actual technical discussion about anything. Just shut up already. You
>>>> think you're so superior when you're just feeding the fire to get
>>>> your own names up in lights.
>>>>
>>>>
>>>If you want time and date to be meaningful - which may or may not be
>>>the case you have to ensure that they are accurate.
>>
>>The OP said, specifically, that he only wanted to keep "order". For that
>>purpose the time and date don't have to be meaningful.
> 
> In which case he needs to set a time that is higher than the last access
> time on any file in the file system. If he uses ext3, 4, xfs or jfs then
> there is journalling, and the file system is in a consistent state when
> you get tl execute something late in the boot process, like rc.local.
> 
> The find/awk/ls/sort script to do this is left as an exercise to the
> reader. (find most recently accessed file, do a stat on it, and set the
> system time to 30 sec in the future from that.)
> 
> If the OP _really_ needs this I can see what I can dig up. I used to do
> this on an altos machine way back before NTP.
> 
> -- mrr
> 
>>>- a battery backed clock that keeps time when the 'puter is off. - use
>>>of some internet accessible clock that you trust to set time on boot
>>>and keep time after boot
>>>- manually or magically setting the clock to the correct time on boot.
> 
> There is a fourth way, if all he wants is a montonically increasing
> time, not necessarily connected with time in other parts of the
> universe.
> 
> Which is what I interpret him to want.
> 
That is correct.

> -- mrr

How can a file become <unsequenced>?
Only by being written, when the rPi's time is less than the time-mark of
some other existing file/s.
JB's idea of marking each written file with the next available <natural 
number:
positive integer>, would achieve the <put each handled paper on top> 
effect.
But using the Files' ID for this is problematic; besides apparently the 
rPi
<keeps time while it's running>.
The only problem is that <its clock stops> when it's powered-down.
AFAICS, provided each rPi-file-write updates the rPi's clock to not be 
less
than the newest file, before it writes; the time-stamps will remain in 
valid
 sequence/order.

The only writes that the particular rPi 'job' does is like:
 mv $1.ogg $1.ogx
so if cp was replaced by: Cp <update rPi's clock>; cp;
wouldn't this 'keep order'?

Looking at the big-picture of the system: rPi + PC
1.   RTC-ed:PC  ==Puts dataFiles to => rPi,  with RealTime stamps;
2.   rPi uses the dataFiles and marks their use-status by marking-their-
ID;
    depending on the RealTimeStage of their usage.
eg. if power is cut while $1.ogg is playing, it becomes marked as z$1.ogg
and if power is cut during the short prompt after playing, it becomes 
$1.ogx

So when rPi goes back to HQ/PC for <reloading and cleaning>, we need the
old & new *.og* not to be mixed i.t.o. their time stamps.

PS. isn't the rPi an educational project?
Who remembers: when UK brought out the mini-car, US advertisers spoke 
about
a 'proper sizes car' [we can use a 2-ton V8 to go to the shop to buy 20
LuckyStrike, cos we've go the infinite frontier...then came toyota....]

WDYS?