[eikenberry]

Anyone have any thoughts on why chrony vs openntpd?

Back when the ntpd security became a thing I evaluated chrony and openntpd as replacements and went with openntpd. It seemed to be simpler, used fewer system resources and had the openbsd teams reputation behind it.

[jlgaddis]

For me, it comes down to the type of hosts I'm dealing with and how accurate I'd prefer their time to be. Years ago, I ran the reference implementation everywhere... but not anymore.

OpenNTPD's goals are to be "good enough" and provide "reasonable accuracy". On an OpenBSD laptop and several "play" VMs (running OpenBSD), it was indeed "good enough". For individual desktops or laptops and the random "standalone" machine, OpenNTPD is simpler and "just works" (I like that it can "verify" the time using HTTPS hosts of my choosing).

Nowadays, only my stratum 1 NTP servers still run the reference implementation. Everything else -- especially hosts which I may need to correlate events based on timestamps -- runs chrony.

A comparison of the three implementations [0] is available on chrony's website. From a quick glance, I don't see anything blatantly incorrect or "biased. The comparison was discussed here on HN ~18 months ago [1].

Basically, if accuracy to the second is good enough, OpenNTPD is fine. If you want more precision than that, go with chrony. It'll be MUCH more accurate and it really isn't any "harder" than OpenNTPD. You'll probably want to stick with ntpd if you're using reference clocks, although chrony supports a subset of them. If you're a nerd that wants the absolutely most accurate time you can get, Google "PTP 1588" as well.

[0]: https://chrony.tuxfamily.org/comparison.html

[1]: https://news.ycombinator.com/item?id=15324386

[eikenberry]

Thanks for the detailed response.

[beagle3]

YMMV, but in my experience, if for whatever reason your clock is wrong by an hour in one direction (either ahead or after, don't remember), openntpd will take ages to skew it back, whereas chrony (and ntpd) do the right thing.

[evil-olive]

openntpd can set the clock on startup, but it requires a non-default `-s` option [0]. In chrony it's optional and controlled by an `initstepslew` parameter [1] which also considers a threshold to determine if the clock needs a large adjustment or if it's fine to just skew it as normal.

0: https://man.openbsd.org/ntpd

1: https://chrony.tuxfamily.org/doc/3.4/chrony.conf.html