The new starting index the oldest sample has index 0; this is the method used to prune old samples when it no longer looks like the measurements fit a linear model. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. The default is just the computer that chronyd itself is running on. Comment 11 Steve Tyler The maxupdateskew parameter is the threshold for determining whether an estimate is too unreliable to be used. Within a configuration file this capability is probably rather moot; however, it is of greater use for reconfiguration at run-time via chronyc see section allow all. Comment 1 Chris Murphy

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Of course, if you can debug the problem yourself and send us a source code patch to fix it, we will be very grateful! On Mac OS X, chronyd must simulate such a capability by periodically slewing the system clock forwards or backwards by a suitable amount to compensate for the error built up since the previous slew. Comment 15 Chris Murphy The second form means that the offline command is to be applied to any source whose IPv4 address is in the 1.

chrony – Frequently Asked Questions

Comment 36 Chris Murphy Version-Release number of selected component if applicable: For computer clocks that is a problem. Comment 20 Steve Tyler It is equivalent to the polltarget option in the server directive in the configuration file see section server. It can be also activated manually by the smoothtime activate command, which is particularly useful when the clock is synchronised only with manual input and the skew is always larger than the threshold.


The directory will be created on start if it does not exist. The number of requests in the burst is limited by the current polling interval to keep the average interval at or above the minimum interval, i.

This is the clock which keeps the time even when your computer is turned off. However, beyond a certain level of delay the measurements are likely to be so corrupted as to be useless. The default is 0 1 second.

Configuring NTP Using the chrony Suite

The parameter is the index of the sample, as shown in the first column of the output from manual list. This can be useful in networks with static configuration to improve the stability of corrections for asymmetric jitter, weighting of the measurements, and the maxdelayratio and maxdelaydevratio tests. An example using shorter polling intervals with a server located in the same LAN could be. Dispersion is due to system clock resolution, statistical measurement variations etc.

If a majority of time sources announce on the last day of June or December that a leap second should be inserted or deleted, it will be accepted even if it is not included in the timezone.

So if chronyd has an existing highly-reliable master estimate and a new estimate is generated which has large dhrony bounds, the existing master estimate will dominate in the new master estimate. If the computer is not turned off for a long time, the RTC should still be close to the true time when the system clock will be initialised from it on the next boot.

Running chrony and rtc

By default, the maximum slew rate is set to In early beta releases of macOS 13 this capability is disabled because of a system kernel bug. I keep getting the error Not authorised Since version 2. They are specified as a numeric mode. To authorize, use the authhash and password commands as follows: The most common option to include in the configuration file is the driftfile option.


The smoothing process is implemented with a quadratic spline function with two or three pieces. It limits the slew rate controlled by the correction time ratio which can be set by the corrtimeratio directive and is effective only on systems where chronyd is able to control the rate i.

However, to avoid frequent reselecting when there are sources with similar distance, a fixed distance is added to the distance for sources that are currently not selected. This is the estimated residual frequency for the server, in parts per million.

This should correspond to the broadcast address of one of the network interfaces on the computer where chronyd is running.

A denial-of-service attack is possible on cjrony symmetric associations, i. You can specify an unprivileged user with the -u option, or the user directive in the chrony. The maxupdateskew directive sets the threshold for determining whether an estimate might be so unreliable that it should not be used.

Some hardware can precisely cross timestamp the NIC clock with the system clock.