Re: [gentoo-user] Simplest NTP client for standalone system?

[Alan McKinnon]

On 29/08/2017 15:57, Rich Freeman wrote:
> On Tue, Aug 29, 2017 at 9:14 AM, Alan McKinnon <alan.mckinnon@×××××.com> wrote:
>>
>> ntp is designed for timeservers that by design do not make the clock
>> jump around. Every second on the wall clock actually happens, none are
>> missing. To do that, ntp adjusts the length of a second till the
>> machine's time creeps up towards the real time as defined by the U.S
>> Navy. Unless you are running software that is extremely time-critical
>> (eg centralized auth servers, science experiments, etc) or you operate a
>> proper time server, you absolutely do not need this behaviour ever.[1]
>>
>
> I'd argue the opposite.  Assuming your system boots with approximately
> the correct time then slewing the clock is going to be the best way to
> maintain time.

Yeah but this is Stroller, and I gave an answer specific to him.

He doesn't run a fleet of business servers in containers like you do, or
maintain awful amounts of ISP infrastructure like I do. He's a regular
guy with regular machines.

We sysadmins can easily tend to get way too involved with the specifics
of how something works and how awesome it all is, and lose sight of what
people really need.

Another example is LVM. You or I might really need it (debatable now we
have ZFS) but the average user has no concept of what it might be, or
care. So why do Ubuntu installers shove it in your face as something
really cool that you should really really use? Because the author of the
installer thinks it's really cool, that's why.

ntpdate in a cron is a really easy way to keep time more or less
accurate. The average user and his software couldn't care less about
slew and couldn't care less if his computer time is 10 seconds off or
even a minute, same with his wristwatch.

But having said that, chrony just does it all without oversight and
without even needing to make a crontab, it's the perfect fire and forget
background daemon. I keep forgetting about chrony (have no real pressing
need to get it at install time)


> Now, if you're talking about a system that starts up with no concept
> of the real time then I'd say the best approach is to do a one-time
> sync to a time server, and then run ntpd from then on to maintain the
> time using slewing.  Obviously you don't want to slew from the epoch
> to the current time.
>
> The one-time sync strikes me as the sort of thing that might ideally
> go into an initramfs.  If you're obtaining your root filesystem over
> the network it might even be a dependency.  Doing it that early
> eliminates most of the issues with logging and running services.
>


-- 
Alan McKinnon
alan.mckinnon@×××××.com