On Sunday 15 March 2020 08:33:30 G.W. Haywood wrote: > Hi there, > > On Sun, 15 Mar 2020, Gene Heskett wrote: > > ... What I wanted was to sync to the debian servers with this > > machine, and then let it broadcast to the rest of the local network, > > Some observations about ntpd and NTP in general: > > 1. Unless you're running a time laboratory, don't use ntpd. Use > chrony. In my experience it's much more forgiving, easier to configure > and does the job it needs to do for those of us who are happy with > accuracies in the order of a couple of milliseconds. I used ntpd for > decades. Since I started using chrony a few years ago it has been > *much* less trouble, and I no longer feel the need to be subscribed to > a 'time' mailing list. This has the happy side-effect that I also > don't need to worry about being berated by some NTP guru for using a > Linux box as a time server. > > 2. If you must use your own server, in addition to them use a pool of > remote time servers such as provided by Debian. You really don't want > the time on your network hunting around following a single rogue box > after it unexpectedly rebooted with the wrong time. Please use the > 'makestep' chrony directive on machines which aren't running 24/7; by > all means use prefer, iburst etc. if you feel the need. > > 3. Enable the (three) chrony logs and look at them often - especially > just after boot, so you get a feel for how quickly you can expect the > time to be recovered. It should be no more than a couple of minutes. > > 4. Use e.g. Nagios/Icinga to monitor things like this. I can let you > have some example graphs privately, and configuration snippets too if > it will help. If the time on any box goes out of spec. I get an email > within minutes. > > > I can add more stratum 2 stuff to this machine, and I can move this > > machine to above the debian servers in the ntp.conf if order helps. > > 5. You shouldn't worry about strata yourself, let the servers do that. > Low strata don't necessarily equate to high accuracy, and vice-versa. > > 6. For a few $currency_units you can add a RTC module to any device > which doesn't have one. I prefer to keep the hardware clock on UTC, > and let the OS and/or application software worry about any timezones, > and especially about changes such as Daylight Saving. With a bit of > effort, the hardware clock will see only the (very) occasional leap > second adjustments. > > 7. See https://en.wikipedia.org/wiki/NTP_server_misuse_and_abuse for > many ways of inadvertently abusing NTP, which you should avoid, and a > few ways of being led down the garden path too (also to be avoided). > > > currently 3 amd64 boxes, and the rpi4. > > I note with interest that you're using a Raspberry Pi 4. In my recent > experience these are particularly flaky compared with other Pis - and, > well, everything else. They really hate disturbances on the USB ports > for example and will hang/crash/reboot/remount-read-only/trash-the-fs > without warning if you should happen to plug in a second USB camera or > disc. It seems to me it's the power conditioning that's at the root > of this, but at the moment I haven't worked with them for long enough > to say much more than that. I'm using Pi 3s for things like my backup > servers, they seem to be much more reliable. I'm writing this mail on > a Pi3b+ which has been my desktop thin client and also a backup server > for some months. It's never put a foot wrong. Even the one venerable > Pi 2 that we have here is more reliable than the 4. The Zeros seem OK > if you don't overtax them, but we tend to use them just for gadgetry. > Or rather _did_ use them. AFAICT at the moment you can't actually buy > one anywhere, and this situation does not seem to be improving; so any > time spent designing with Zeros seems to have been pretty much wasted.
This instant reboot thing is the first time I have had anything happen to any pi in the 3 or higher category. With a ups, until now, rebooting has absolutely been at my pleasure. I can't say the same for my 3 wintel boxes running other machines. I went to a pi4 for this because the pi3 was doing a pretty good jub but dragging its tongue on the floor, whereas the pi4, at a fixed 800MHz, is effectively parked in a beach chair under an umbrella, feet up and Martini in hand, up till now. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>
