Re: What TZ do you use to get right time w/ clockspeed?

2002-11-14-17:34:43 Paul Jarc:
> > rather than to the variable, moving-epoch UTC-10secs or whatever it
> > is that POSIX mandates?
> 
> Nobody uses a moving epoch; anything that moves is not an epoch at
> all.  POSIX and the Olson right/ zones use the same epoch, I think:

I _think_ that POSIX requires that time(2) skip leap seconds, while
the Olson right/ zones (and libtai with /etc/leapsecs.dat present)
require that time(2) advance every second, getting another second
out of date whenever there's a leap second.

"anything that moves is not an epoch at all" => POSIX is plughed.

> > Another, which might be more acceptable in some contexts, would be
> > to leave the system clock behaving as POSIX mandates. Removing
> > /etc/leapsecs.dat seems to do that.
> 
> That will put your system clock in sync with other POSIX clocks.  But
> when a leap second comes along, NTP-sync'ed machines will jump;
> [...]

Followin POSIX's mandates...

> [...] your clockspeed-regulated clock will move smoothly to the
> new time, after you've fed it a correction from sntpclock.  It
> would be best to restart clockspeed just before giving it this
> adjustment, to ensure that etc/atto isn't distorted.

I definitely agree with that; a good sound comprehensive system
solution using clockspeed, sntpdate, and leapsecs.dat with
TZ=right/... would also involve stopping clockspeed before each and
every leap second, and not restarting it until you've gotten a good
resync off an NTP server, then restarting it with the original start
protocol, an up-front adjust from sntpclock, then additional ones at
increasing time spans after until you get all nice and locked up
again.

> Your TAI64[N[A]] labels will not agree with those from true TAI-clock
> machines at the "same" time, though.

If anything except djb libtai clients used TAI, I'd find this a
greater concern. Do you know of any other software using TAI? I've
not been able to find any. So the sick perversion of TAI "TAI warped
through however many seconds POSIX mandates skipping" would seem to
be consistently usable, if nasty, and riddled with these idiot clock
leaps every few years.

> You might be better off by simply avoiding libtai-based software
> on POSIX-clock machines.

Given a machine might have to be a POSIX-clock machine because,
e.g., you want consistent log timestamps enterprise-wide, and some
devices in the enterprise might be forced to stay POSIX, I'd _still_
like to use clockspeed on it.

Maybe it'd make the very most beautiful (or the least ugly, take
your pick :-) sense, in such a case, to just reach into sntpclock
and butcher its brain, blinding it to leapsecs.dat, so it syncs
POSIXly, but leave leapsecs.dat in place and let the rest of the
libtai machinery Rest In Peace.

-Bennett

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.0.7 (GNU/Linux)

iD4DBQE91F9jHZWg9mCTffwRAgV/AJjWlWb+InqeZ2OGCuIKgysPE3OkAJ9BLH8X
KgtMG+j2rnQ14MuFqm2eQw==
=U4Bd
-----END PGP SIGNATURE-----