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When you do not want to start [application]*phc2sys* as a service, you can start it from the command line. For example, enter the following command as `root`:
Where _em3_ is the interface you want to check.
Where _em3_ is the interface you want to configure. Below is example output from [application]*ptp4l* when the `PTP` clock on the NIC is synchronized to a master:
Where _summary-updates_ is the number of clock updates to include in summary statistics. An example follows:
With hardware `PTP` support, the NIC has its own on-board clock, which is used to time stamp the received and transmitted `PTP` messages. It is this on-board clock that is synchronized to the `PTP` master, and the computer's system clock is synchronized to the `PTP` hardware clock on the NIC. With software `PTP` support, the system clock is used to time stamp the `PTP` messages and it is synchronized to the `PTP` master directly. Hardware `PTP` support provides better accuracy since the NIC can time stamp the `PTP` packets at the exact moment they are sent and received while software `PTP` support requires additional processing of the `PTP` packets by the operating system.
With hardware time stamping, [application]*phc2sys* needs to be used to synchronize the `PTP` hardware clock to the system clock. If running [application]*phc2sys* as a service, edit the `/etc/sysconfig/phc2sys` configuration file. The default setting in the `/etc/sysconfig/phc2sys` file is as follows: