Processes Known to Adjust the System Clock

Enhanced PTP User Guide (UG1602)

Document ID
UG1602
Release Date
2022-10-18
Revision
1.0 English

The following processes are known to adjust the system clock.

Centrify

This is Windows Active Directory integration for Linux systems providing centralized identification and access management to servers.

To prevent Centrify from adjusting the system clock, disable sntp in the Active Directory configuration using the following setting:

FILE: /etc/centrifydc/centrifydc.conf/
PARAMETER: adclient.sntp.enabled false

A restart of the Centrify/Active Directory service is required following the change.

Quest

Another product extending Active Directory authentication services across Linux platforms.

PBIS

PowerBroker Identify Services is a further product offering Windows Active Directory authentication services to Linux platforms.

systemd-timesyncd

This is a daemon that implements an SNTP client which achieves a low quality time synchronization of the system clock. The SNTP client can step and adjust the system clock.

systemd-timedated

This is a service that can be used to change the system clock and timezone, as well as to enable/disable NTP time synchronization. This service is activated on request and is self-terminating when unused.

chronyd

chronyd is a daemon implementation of NTP. It can be used to synchronize the system clock with NTP servers or reference clocks. See also Chronyd.

phc2sys

phc2sys is a Linux program which is able to synchronize two clocks in a system. Typically this is used to synchronize the system clock with a PTP hardware clock.

NTP

When running sfptpd, the NTP service should only be enabled when this service is required by the sfptpd mode i.e. when running in NTP/PPS mode or an NTP fallback mode.

At startup, sfptpd will warn you and exit if the NTP service is running, but is not required by the sfptpd mode being used.

tuned Profiles

Some tuned profiles might activate any of the services listed above, or other services which interact with the system clock. Profiles are normally stored in the /usr/lib/tuned directory.