Impact of multiple NTP implementations in containers on host chronyd
"Valera Requena, Juan" <[email protected]> Fri, 16 Jan 2026 13:04:24 +0000
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Hi everyone,
I have a setup where the host runs chronyd natively to discipline the syste=
m clock. However, we have several applications running in containers, and f=
or various legacy reasons, some of these containers include their own NTP i=
mplementations (like ntpd, sntp, or even other chronyd instances).
My main concerns are:
1.
Will these containerized NTP clients interfere with the host's chronyd abil=
ity to maintain a stable clock?
2.
Since they share the same kernel, is there a risk of "clock fighting" if a =
container has enough privileges to call adjtimex or settimeofday?
3.
What is the recommended way to handle this? Should we strictly disable time=
-setting capabilities in all containers?
Any insights or best practices would be greatly appreciated.
Best regards, Juan.
[INDRA]<http://www.indracompany.com/>
Juan Valera Requena
ATM / CNS
indracompany.com<http://www.indracompany.com/>
[LinkedIn]<http://www.linkedin.com/company/indra>
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p%5Eserp%7Ctwgr%5Eauthor>
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[Instagram]<https://www.instagram.com/indracompany/?hl=3Des>
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Hi everyone,</div>
<div style=3D"margin-top: 1em; margin-bottom: 1em; font-family: Aptos, Apto=
s_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-s=
ize: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof">
I have a setup where the host runs <code>chronyd</code> natively =
to discipline the system clock. However, we have several applications runni=
ng in containers, and for various legacy reasons, some of these containers =
include their own NTP implementations (like
<code>ntpd</code>, <code>sntp</code>, or even other <code>chronyd</code>&nb=
sp;instances).</div>
<div style=3D"margin-top: 1em; margin-bottom: 1em; font-family: Aptos, Apto=
s_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-s=
ize: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof">
My main concerns are:</div>
<ol data-path-to-node=3D"9" start=3D"1">
<li style=3D"font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, C=
alibri, Helvetica, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);">
<div style=3D"margin-top: 1em; margin-bottom: 1em;" role=3D"presentation" c=
lass=3D"elementToProof">
Will these containerized NTP clients interfere with the host's <code>chrony=
d</code> ability to maintain a stable clock?</div>
</li><li style=3D"font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontServi=
ce, Calibri, Helvetica, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);">
<div style=3D"margin-top: 1em; margin-bottom: 1em;" role=3D"presentation" c=
lass=3D"elementToProof">
Since they share the same kernel, is there a risk of "clock fighting&q=
uot; if a container has enough privileges to call
<code>adjtimex</code> or <code>settimeofday</code>?</div>
</li><li style=3D"font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontServi=
ce, Calibri, Helvetica, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);">
<div style=3D"margin-top: 1em; margin-bottom: 1em;" role=3D"presentation" c=
lass=3D"elementToProof">
What is the recommended way to handle this? Should we strictly disable time=
-setting capabilities in all containers?</div>
</li></ol>
<div style=3D"margin-top: 1em; margin-bottom: 1em; font-family: Aptos, Apto=
s_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-serif; font-s=
ize: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof">
Any insights or best practices would be greatly appreciated.</div>
<div style=3D"font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, =
Calibri, Helvetica, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);" clas=
s=3D"elementToProof">
Best regards, Juan.</div>
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Calibri, Helvetica, sans-serif; font-size: 11pt; color: rgb(0, 0, 0);" clas=
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<b>Juan Valera Requena</b></p>
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ATM / CNS</p>
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