[ntp:questions] ntpd 4.2.7p230 defaults to ignoring ntpdc queries

Dave Hart hart at ntp.org
Sat Nov 5 17:02:47 UTC 2011

On Sat, Nov 5, 2011 at 15:45, steven Sommars <stevesommarsntp at gmail.com> wrote:
> Dave,
> How do you see the ntpdc (/ntpd/ntpdc)  transition happening?      [I expect
> most post 4.2.7p230 ntpd builds to use the default options]
> http://www.eecis.udel.edu/~mills/ntp/html/ntpdc.html makes no mention of an
> upcoming obsolescence/deprecation and likely few ntpdc users have planned
> for it.     Was there an announcement or web page?  ntpdate is covered
> in https://support.ntp.org/bin/view/Dev/DeprecatingNtpdate .
>   https://support.ntp.org/bin/view/Dev/DeprecatingNtpdc is only a
> placeholder.

ntpdc.html does need to be updated to reflect the fact that ntpd
4.2.7p230 and later default to ignoring ntpdc queries.  I didn't do so
sooner because I was waiting for all its functionality to be mirrored
in ntpq.  There has not been an announcement of ntpdc deprecation
until now, but there has been discussion about it for years.  See
these messages for examples:


> To query a mix of ntpd server versions will now require use of a new ntpq
> and a (deprecated) ntpdc and logic to determine which to use.    Smoother
> transition schemes are possible but may run counter to the simplification
> goals.

That is true for the types of queries previously supported only by
ntpdc.  I believe for the vast majority of operator queries, a recent
ntpq can be used to query both older and newer ntpd.  Also, while
ntpdc is now deprecated, it is still part of the distribution, so
newer systems can still be used to query previously ntpdc-only
information from older ntpd instances.

Given a specific scenario, I'd be happy to look at how best to query a
mixed flock where some ntpd instances expose some information only via
mode 7/ntpdc.

> With its smaller user base deprecating ntpdc should be less contentious than
> ntpdate was.  I don't object to the changes(mode 7 is ugly), but believe
> that some documentation work (e.g,. in DeprecatingNtpdc) may be worthwhile.
> Steve Sommars

The documentation I am most concerned with getting right is the HTML
documentation distributed with the reference implementation, the
latest version of which is published on Dr. Mills' site:


ntpdc.html is probably the best place to put advice about querying
mixed flocks.  I appreciate your attention to this issue.

Dave Hart

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