[Bug 999725] Re: broken start-up dependencies for ntp

[Nathan Stratton Treadway]

On Fri, May 18, 2012 at 17:47:21 -0000, Paul Crawford wrote:
> I think this bug should concentrate on the key issue:
> that ntp (and maybe others?) is being brought up on the
> wrong event, that is it comes up with the interface, and
> not with the chosen type of name server.

More specifically, the ntp package has not been converted
to Upstart yet, so it just comes up as part of the
rc-sysvinit scripts.  That is, ntpd's startup itself isn't
tied to any specific event(s) at all (though as Steve's
comment hinted at, the execution of the rc-sysvinit scripts
as a group is triggered by the "filesystem and
static-network-up" condition).

I'm not sure off hand how the decision is made whether to
convert a package such as ntp to Upstart... but I see a
couple other bugs open on the topic: LP #604717 , LP #913379


> In our case NIS provides user and name server resolution,
> and ntp comes up before it with 12.04

(As far as I can tell, the NIS and ntp start conditions are
the same in Lucid and Precise, so I wonder if the reason
you don't see this problem on your Lucid machine is that
DNS is configured there.)
 

> I don't know how LDAP is handled, but from the above
> comments it would appear be have the same problem, and so
> ntp is not currently able to resolve machines given only
> by NIS (or LDAP) name if they are not in the DNS (which I
> guess might be common with a large private network behind
> NAT).

One thing to note is that ntp does spawn a separate process
that continues to retry looking up host names until it
finds an answer, so normally it will recover gracefully if
the lookup fails when ntp first starts up but start to work
later on.

I'm not sure of the details of how that interacts with
NIS-based host resolution, but I suspect this resolver
process doesn't deal with the NIS-is-not-ready-yet
situation the same way it does for DNS.

Anyway, I suspect that it's pretty rare for a site to have
no DNS at all, and that's probably why this issue hasn't
shown up for other people.

(Also, I don't know if there's an automated way for the
system to detect that ntp needs NIS to be up, so probably
such a dependency wouldn't be found in a default
installation.  But if ntp were converted to Upstart, it
would be much easier for the system administrator to add
that dependency manually....)

                                                Nathan


** Summary changed:

- broken start-up dependencies for ntp
+ broken start-up dependencies for ntp (starts before NIS is available)

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https://bugs.launchpad.net/bugs/999725

Title:
  broken start-up dependencies for ntp (starts before NIS is available)

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