[chrony-users] Chrony client on host with server running in LXC on same host

[Joachim Tingvold <joachim@xxxxxxxxxxxx>]

Hi,

Stumbled upon the recent discussion about running multiple layers of ntp services[1], and also an older discussion[2] regarding feedback loops even when running with the -x flag.

I have a scenario where I have multiple physical Linux hosts (10+ for the sake of this discussion), which I was planning to run chrony in “client mode” syncing with “ntp1.foo.bar” and “ntp2.foo.bar”. These two ntp-servers (ntp1+2) will be running inside an LXC-container on two out of the 10+ hosts, and source their time from external NTP-servers.

My interpretation of how the -x flag worked, was that it basically ignored the system time, and only used the virtual software clock (“NTP clock”) to serve NTP clients with. Based on the two aforementioned discussions, that doesn’t seem to be the case (i.e. it still relies on the system clock, even if the server doesn’t attempt to set it).

I also noticed that the 4.7 changelog mentions “Detect clock interference from other processes”. Is this something that would solve these feedback loops in the scenario I’m describing?

If not, what should the chrony-config look like on the client (hosts) and server (ntp1+2)? Would it be possible to have equal config on all hosts (regardless if ntp1+2 is running as LXC container on said host or not), to ease config-deployment of chrony on the hosts? Preferably a setup where only ntp1+2 has access to the external NTP-servers (i.e. hosts will not).


[1] <https://listengine.tuxfamily.org/chrony.tuxfamily.org/chrony-users/2026/01/msg00003.html>
[2] <https://listengine.tuxfamily.org/chrony.tuxfamily.org/chrony-users/2024/10/msg00002.html>

-- 
Joachim

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