[pkg-ntp-maintainers] Bug#823533: allow to skip ntpdate on ifup

[Christian Ehrhardt]

On Tue, Jan 2, 2018 at 10:22 PM, Bernhard Schmidt <berni at debian.org> wrote:
> On Thu, May 05, 2016 at 01:44:06PM -0500, Christian Ehrhardt wrote:
>
> Hi Christian,
>
> thanks for bringing this up.
>
>> While these days the systemd based timesync* tools are doing most of the
>> work there is still a lot of buzz around the automated ntpdate on ifup
>> being good/bad for various reasons.
>>
>> I'll try to to summarize the outcome of multiple discussions and bugs
>> around this that I recently passed and propose a solution.
>
> I think we even need a few more changes around here.
>
> First of all, we need to change the actual binary for a one-shot time
> sync from the long deprecated ntpdate to sntp.
>
> If we use sntp with the default configuration it uses an unpriviledged
> port, which should not race the startup of ntpd anymore. So we could get
> rid of all the locking. I've posted a mail regarding this on the mailing
> list a couple of months ago.
>
> https://lists.alioth.debian.org/pipermail/pkg-ntp-maintainers/2017-October/004850.html
>
> Third, I think a major issue is the package "ntpdate" both shipping the
> ntpdate binary (which one might want to use for debugging or because you
> just don't know sntp) and the ifup hooks, which simply do not work well
> with a lot of use cases. I'm pretty sure that most installations of
> ntpdate do not need it.
>
> I'm therefor proposing a complete rewrite
>
> - new package sntp-hooks
>   - depends on sntp, ships hooks for ifupdown and possibly others (like
>     NetworkManager or systemd-network or whatever Ubuntu is doing now)
>   - executes the actual sntp synchronisation non-blocking, possibly with
>     a one-shot systemd unit using --no-block when systemd is running
> - make ntpdate depend on sntp-hooks and rm_conffile all installed hooks
>
> So if you don't want hooks you just don't install sntp-hooks.
>
> The package sntp-hooks could additionally ship an /etc/default file to
> change behaviour.
>
> I have attempted to spin up some patches for this lately, but ran out of
> time. Is this something you could agree on Ubuntu-side?

Hi Bernhard,
first of all thanks for your participation and help!

Yes - on the isolated view to ntp* I think the proposed changes make sense.
Now that we have sntp (back) I think it makes sense to use it instead, but as
you already outlined that needs some extra work to behave mostly "like
people are used from ntpdate".

I like the suggestion to make the hooks an extra package.
And yes in Ubuntu (and any system dropping ifup/down down the road I
guess) it will be as in [1] "How can I add pre-up, post-up, etc. hook scripts?"
Doing that in a new and non enforced package sounds great, for there
always will be >0 people who don't want hooks to run.

I said "on the isolated view to ntp*" since most of what the ntpdate hooks
provided is covered by systemd-timesyncd these days it is also way less
important in most usual setups. But OTOH that provides some freedom
not being forced to make those new sntp/hooks the total generic swiss
army knife.

[1]: https://wiki.ubuntu.com/Netplan#Frequently-asked_questions


-- 
Christian Ehrhardt
Software Engineer, Ubuntu Server
Canonical Ltd