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    SubjectRe: [ntpwg] Bug: Status/Summary of slashdot leap-second crash on new years 2008-2009
    From
    In message: <20090112161115.GA1474@ucw.cz>
    Pavel Machek <pavel@suse.cz> writes:
    : On Mon 2009-01-05 11:42:35, Linas Vepstas wrote:
    : > 2009/1/5 <david@lang.hm>:
    : > > On Mon, 5 Jan 2009, Linas Vepstas wrote:
    : > >
    : > >>> Arguably the kernel's responsibility should be to keep track of the
    : > >>> most fundamental representation of time possible for a machine (that's
    : > >>> probably TAI) and it is a userspace responsibility to map from that
    : > >>> value to other time standards including UTC,
    : > >>
    : > >> Yes, this really does seem like the right solution.
    : > >>
    : > >>> using control files
    : > >>> which are updated as leap seconds are declared.
    : > >>
    : > >> Lets be clear on what "control files" means. This does
    : > >> *NOT* mean some config file shipped by some distro
    : > >> for some package. That would be a horrid solution.
    : > >> People don't install updates, patches, etc. Distros
    : > >> ship them late, or never, if the distro is old enough.
    : > >>
    : > >> A more appropriate solution would be to have
    : > >> either the kernel or ntpd track the leap seconds
    : > >> automatically. First, the ntp protocol already provides
    : > >> the needed notification of a leap second to anyone
    : > >> who cares about it (i.e. there is no point in getting a
    : > >> Linux distro involved in this -- a distribution mechanism
    : > >> already exists, and works *better* than having a distro
    : > >> do it).
    : > >
    : > > I disagree with this. NTP will only know about leap seconds if it was
    : > > running and connected to a server that advertised the leap seconds during
    : > > that month.
    : > >
    : > > for example, if you installed a new server today, how would it ever know
    : > > that there was a leap second a couple of days ago?
    : >
    : > OK, good point. Unless your distro was less
    : > than a few days old (unlikely), you are faced with the
    : > same problem. Sure, eventually, the distro will publish
    : > an update (which will add to the existing list of 36 leap
    : > seconds -- which is needed in any case, since no one
    : > has a server that's been up since 1958), but this is
    : > unlikely to happen during this install window.
    : >
    : > The long term solution would be write an RFC to extend
    : > NTP to also provide TAI information -- e.g. to add a
    : > message that indicates the current leap-second offset
    : > between UTC and TAI.
    :
    : Offset is not enough; you'd have to provide list of all previous leap
    : seconds with 'when it happened' timestamps.

    Well, today you can ftp the leapseconds.txt file from NIST. Of
    course, that assumes your machine is on the network, and not a dumb
    slave of a smart head-end that's off the net...

    Warner


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