[PVE-User] NTP on PVE8...

[DERUMIER, Alexandre]

basically, systemd-timesync is a simple pool sntp client  

https://github.com/systemd/systemd/blob/v213/NEWS#L5

A new "systemd-timesyncd" daemon has been added for
          synchronizing the system clock across the network. It
          implements an SNTP client. In contrast to NTP
          implementations such as chrony or the NTP reference server
          this only implements a client side, and does not bother with
          the full NTP complexity, focusing only on querying time from
          one remote server and synchronizing the local clock to
          it. Unless you intend to serve NTP to networked clients or
          want to connect to local hardware clocks this simple NTP
          client should be more than appropriate for most
          installations. The daemon runs with minimal privileges, and
          has been hooked up with networkd to only operate when
          network connectivity is available. The daemon saves the
          current clock to disk every time a new NTP sync has been
          acquired, and uses this to possibly correct the system clock
          early at bootup, in order to accommodate for systems that
          lack an RTC such as the Raspberry Pi and embedded devices,
          and make sure that time monotonically progresses on these
          systems, even if it is not always correct. To make use of
          this daemon a new system user and group "systemd-timesync"
          needs to be created on installation of systemd.


Ntp implement incremental time increase/decrease. You really want that
(not big time jump), if you want stable virtualisation (Hello windows
BSOD).


Redhat use chrony on rhel server distro.




-------- Message initial --------
De: Marco Gaiarin <gaio at lilliput.linux.it>
Répondre à: Proxmox VE user list <pve-user at lists.proxmox.com>
À: pve-user at lists.proxmox.com
Objet: Re: [PVE-User] NTP on PVE8...
Date: 19/08/2024 17:50:29

Mandi! Alwin Antreich
  In chel di` si favelave...

> systemd-timesyncd only uses one server to update its time, which can
> lead to
> time jumps when this NTP can't be accessed reliably. NTPs (eg.
> ntpd/chrony) are
> usually using 3+ servers to calculate a mean time and compensate for
> jitter and
> other delays.

systemd-timesyncd does not use one server, have also fallback one (or
use
round robin); surely 'mean/compensate' is better then fallback and
round
robin, but...

> This allows to keep the time more stable and especially helps
> when Ceph or HA is enabled. ;)

...clearly i'm speaking of standalone server or non-HA, non-Ceph
clusters!


Anyway, the statement:

> > WARN: systemd-timesyncd is not the best choice for time-keeping on
> > servers, due to only applying updates on boot.

it is not true: i suggest to remove at least 'due to only applying
updates on boot'.


(clearly, for future 'pve8to9' scripts... ;-)