SLES 15 SP2 | System Analysis and Tuning Guide | Precision Time Protocol

PTP requires that the used kernel network driver supports either software or hardware time stamping. Moreover, the NIC must support time stamping in the physical hardware. You can verify the driver and NIC time stamping capabilities with ethtool :

ptp4l uses hardware time stamping by default. As
root, you need to specify the network interface capable of hardware
time stamping with the -i option. The -m
tells ptp4l to print its output to the standard output
instead of the system’s logging facility:

> sudo ptp4l -m -i eth0
selected eth0 as PTP clock
port 1: INITIALIZING to LISTENING on INITIALIZE
port 0: INITIALIZING to LISTENING on INITIALIZE
port 1: new foreign master 00a152.fffe.0b334d-1
selected best master clock 00a152.fffe.0b334d
port 1: LISTENING to UNCALIBRATED on RS_SLAVE
master offset -25937 s0 freq +0 path delay       12340
master offset -27887 s0 freq +0 path delay       14232
master offset -38802 s0 freq +0 path delay       13847
master offset -36205 s1 freq +0 path delay       10623
master offset  -6975 s2 freq -30575 path delay   10286
port 1: UNCALIBRATED to SLAVE on MASTER_CLOCK_SELECTED
master offset  -4284 s2 freq -30135 path delay    9892

The master offset value represents the measured offset
from the master (in nanoseconds).

The s0, s1, s2
indicators show the different states of the clock servo:
s0 is unlocked, s1 is clock step, and
s2 is locked. If the servo is in the locked state
(s2), the clock will not be stepped (only slowly
adjusted) if the pi_offset_const option is set to a
negative value in the configuration file (see man 8
ptp4l for more information).

The freq value represents the frequency adjustment of
the clock (in parts per billion, ppb).

The path delay value represents the estimated delay of
the synchronization messages sent from the master (in nanoseconds).

Port 0 is a Unix domain socket used for local PTP management. Port 1 is the
eth0 interface.

INITIALIZING, LISTENING,
UNCALIBRATED and SLAVE are examples
of port states which change on INITIALIZE,
RS_SLAVE, and MASTER_CLOCK_SELECTED
events. When the port state changes from UNCALIBRATED to
SLAVE, the computer has successfully synchronized with a
PTP master clock.

You can enable software time stamping with the -S option.

> sudo ptp4l -m -S -i eth3

You can also run ptp4l as a service:

> sudo systemctl start ptp4l

In this case, ptp4l reads its options from the
/etc/sysconfig/ptp4l file. By default, this file tells
ptp4l to read the configuration options from
/etc/ptp4l.conf. For more information on
ptp4l options and the configuration file settings, see
man 8 ptp4l.

To enable the ptp4l service permanently, run the
following:

> sudo systemctl enable ptp4l

To disable it, run

> sudo systemctl disable ptp4l