Questions about "holdover" state
"Valera Requena, Juan" <[email protected]> Mon, 12 Jan 2026 11:29:24 +0000
| Newsgroups | gmane.comp.time.chrony.user |
|---|---|
| Message-ID | <PAXP193MB1325AA6B6C77A2C38D0B0293D581A@PAXP193MB1325.EURP193.PROD.OUTLOOK.COM> |
--_000_PAXP193MB1325AA6B6C77A2C38D0B0293D581APAXP193MB1325EURP_
Content-Type: text/plain; charset="Windows-1252"
Content-Transfer-Encoding: quoted-printable
Hello,
I am trying to better understand how chronyd behaves when all reference sou=
rces become unavailable, specifically regarding holdover behavior.
By holdover I mean the situation in which the host was synchronized to one =
or more NTP sources, and then loses connectivity to all reference servers, =
continuing to discipline or free-run the clock based on its last known stat=
e.
I have two related questions:
1.
Identification of holdover state
Is there a way to explicitly identify that chronyd is operating in a holdov=
er state using chronyc or chronyd status information?
For example:
* Is there a specific flag, status field, or command output that ind=
icates =93synchronized but no reachable sources=94?
* Should this be inferred indirectly (e.g., from source reachability=
, Leap status, or Reference ID)?
2.
Transition from holdover to unsynchronized
How does chronyd internally determine when a system, while in holdover, tra=
nsitions to a non-synchronized state?
* Is this based on a maximum estimated error, time since last valid =
measurement, root dispersion growth, or another threshold?
* Are there configuration parameters that influence this decision (e=
.g., limits on acceptable uncertainty or timeout values)?
In short, I would like to understand:
* How to reliably detect that chronyd is in holdover, and
* What criteria chronyd uses to decide that the clock is no longer cons=
idered synchronized once all reference sources remain unavailable for some =
time.
Any clarification or pointers to relevant documentation or source code woul=
d be greatly appreciated.
Thank you!
________________________________
Este correo electr=F3nico y, en su caso, cualquier fichero anexo al mismo, =
contiene informaci=F3n de car=E1cter confidencial exclusivamente dirigida a=
su destinatario o destinatarios. Si no es vd. el destinatario indicado, qu=
eda notificado que la lectura, utilizaci=F3n, divulgaci=F3n y/o copia sin a=
utorizaci=F3n est=E1 prohibida en virtud de la legislaci=F3n vigente. En el=
caso de haber recibido este correo electr=F3nico por error, se ruega notif=
icar inmediatamente esta circunstancia mediante reenv=EDo a la direcci=F3n =
electr=F3nica del remitente.
Evite imprimir este mensaje si no es estrictamente necesario.
This email and any file attached to it (when applicable) contain(s) confide=
ntial information that is exclusively addressed to its recipient(s). If you=
are not the indicated recipient, you are informed that reading, using, dis=
seminating and/or copying it without authorisation is forbidden in accordan=
ce with the legislation in effect. If you have received this email by mista=
ke, please immediately notify the sender of the situation by resending it t=
o their email address.
Avoid printing this message if it is not absolutely necessary.
--_000_PAXP193MB1325AA6B6C77A2C38D0B0293D581APAXP193MB1325EURP_
Content-Type: text/html; charset="Windows-1252"
Content-Transfer-Encoding: quoted-printable
<html>
<head>
<meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3DWindows-1=
252">
<style type=3D"text/css" style=3D"display:none;"> P {margin-top:0;margin-bo=
ttom:0;} </style>
</head>
<body dir=3D"ltr">
<div style=3D"line-height: 20px; margin-top: 1em; margin-bottom: 1em; font-=
family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica,=
sans-serif; font-size: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof=
">
Hello,</div>
<div style=3D"line-height: 20px; margin-top: 1em; margin-bottom: 1em; font-=
family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica,=
sans-serif; font-size: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof=
">
I am trying to better understand how <b>chronyd</b> behaves when all r=
eference sources become unavailable, specifically regarding
<i>holdover</i> behavior.</div>
<div style=3D"line-height: 20px; margin-top: 1em; margin-bottom: 1em; font-=
family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica,=
sans-serif; font-size: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof=
">
By <i>holdover</i> I mean the situation in which the host <b>was synch=
ronized</b> to one or more NTP sources, and then
<b>loses connectivity to all reference servers</b>, continuing to disciplin=
e or free-run the clock based on its last known state.</div>
<div style=3D"line-height: 20px; margin-top: 1em; margin-bottom: 1em; font-=
family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica,=
sans-serif; font-size: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof=
">
I have two related questions:</div>
<ol 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"line-height: 20px; margin-top: 1em; margin-bottom: 1em;" role=
=3D"presentation" class=3D"elementToProof">
<b>Identification of holdover state</b><br>
Is there a way to explicitly identify that chronyd is operating in a <i>hol=
dover</i> state using
<code>chronyc</code> or chronyd status information?<br>
For example:</div>
</li><ul>
<li style=3D"font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, C=
alibri, Helvetica, sans-serif; font-size: 11pt; color: rgb(0, 0, 0); line-h=
eight: 20px;">
Is there a specific flag, status field, or command output that indicates =
=93synchronized but no reachable sources=94?</li><li style=3D"font-family: =
Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sans-se=
rif; font-size: 11pt; color: rgb(0, 0, 0); line-height: 20px;">
Should this be inferred indirectly (e.g., from source reachability, <code>L=
eap status</code>, or
<code>Reference ID</code>)?</li></ul>
<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"line-height: 20px; margin-top: 1em; margin-bottom: 1em;" role=
=3D"presentation" class=3D"elementToProof">
<b>Transition from holdover to unsynchronized</b><br>
How does chronyd internally determine when a system, while in holdover, tra=
nsitions to a
<b>non-synchronized</b> state?</div>
</li><ul>
<li style=3D"font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, C=
alibri, Helvetica, sans-serif; font-size: 11pt; color: rgb(0, 0, 0); line-h=
eight: 20px;">
Is this based on a maximum estimated error, time since last valid measureme=
nt, root dispersion growth, or another threshold?</li><li style=3D"font-fam=
ily: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica, sa=
ns-serif; font-size: 11pt; color: rgb(0, 0, 0); line-height: 20px;">
Are there configuration parameters that influence this decision (e.g., limi=
ts on acceptable uncertainty or timeout values)?</li></ul>
</ol>
<div style=3D"line-height: 20px; margin-top: 1em; margin-bottom: 1em; font-=
family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica,=
sans-serif; font-size: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof=
">
In short, I would like to understand:</div>
<ul>
<li style=3D"font-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, C=
alibri, Helvetica, sans-serif; font-size: 11pt; color: rgb(0, 0, 0); line-h=
eight: 20px;">
How to reliably detect that chronyd is in holdover, and</li><li style=3D"fo=
nt-family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helveti=
ca, sans-serif; font-size: 11pt; color: rgb(0, 0, 0); line-height: 20px;">
What criteria chronyd uses to decide that the clock is no longer considered=
synchronized once all reference sources remain unavailable for some time.<=
/li></ul>
<div style=3D"line-height: 20px; margin-top: 1em; margin-bottom: 1em; font-=
family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica,=
sans-serif; font-size: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof=
">
Any clarification or pointers to relevant documentation or source code woul=
d be greatly appreciated.</div>
<div style=3D"line-height: 20px; margin-top: 1em; margin-bottom: 1em; font-=
family: Aptos, Aptos_EmbeddedFont, Aptos_MSFontService, Calibri, Helvetica,=
sans-serif; font-size: 11pt; color: rgb(0, 0, 0);" class=3D"elementToProof=
">
Thank you!</div>
<div class=3D"elementToProof"></div>
<br>
<hr>
<font face=3D"Arial" color=3D"Gray" size=3D"1"><br>
Este correo electr=F3nico y, en su caso, cualquier fichero anexo al mismo, =
contiene informaci=F3n de car=E1cter confidencial exclusivamente dirigida a=
su destinatario o destinatarios. Si no es vd. el destinatario indicado, qu=
eda notificado que la lectura, utilizaci=F3n,
divulgaci=F3n y/o copia sin autorizaci=F3n est=E1 prohibida en virtud de l=
a legislaci=F3n vigente. En el caso de haber recibido este correo electr=F3=
nico por error, se ruega notificar inmediatamente esta circunstancia median=
te reenv=EDo a la direcci=F3n electr=F3nica del
remitente.<br>
Evite imprimir este mensaje si no es estrictamente necesario.<br>
<br>
This email and any file attached to it (when applicable) contain(s) confide=
ntial information that is exclusively addressed to its recipient(s). If you=
are not the indicated recipient, you are informed that reading, using, dis=
seminating and/or copying it without
authorisation is forbidden in accordance with the legislation in effect. I=
f you have received this email by mistake, please immediately notify the se=
nder of the situation by resending it to their email address.<br>
Avoid printing this message if it is not absolutely necessary.<br>
</font>
</body>
</html>
--_000_PAXP193MB1325AA6B6C77A2C38D0B0293D581APAXP193MB1325EURP_--
--
To unsubscribe email chrony-users-request-kWFZVVI9zxvPqho9SqqRMmD2FQJk+8+b@public.gmane.org
with "unsubscribe" in the subject.
For help email chrony-users-request-kWFZVVI9zxvPqho9SqqRMmD2FQJk+8+b@public.gmane.org
with "help" in the subject.
Trouble? Email [email protected]