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Linux Driver for Precision Clock Virtual Device

ptp_vmw is a Linux driver for VMware Precision Clock, a new type of virtual device available in ESXi 7.0 (hardware version 17 on-wards) that provides virtual machines with access to the underlying ESXi host's system clock. Guests can use the device as a reference clock in Chrony time synchronization software to synchronize their system clocks with.

Precision Clock offers an alternative to existing methods of time synchronization in the guest, such as NTP. A potential benefit of using Precision Clock, when compared to a network time synchronization, is that it uses a VMware proprietary paravirtual interface between a virtual machine and the host to fetch time information. Achievable accuracy using network based time synchronization in a guest is limited by delay and variability in the virtual networking paths (including the guest's own networking stack), especially under high loads. By avoiding virtual networking, time synchronization using Precision Clock can, potentially, achieve higher accuracy. See the vSphere 7.0 documentation at for more information about this virtual device.

This fling includes a Linux kernel module source RPM, which can be built and installed in a Linux system. Upon loading the driver, a PTP clock device is created, which can be consumed as a reference clock in Chrony. See included README file for more information.

To use the driver, please download the file into your VM. Please unzip the ZIP file. It will expand into a source RPM file and a README file. Please follow instructions in the README file to install the driver.

  • VMware ESXi 7.0
  • Virtual Machine(hardware version 17 or above), running one of the following guest operating systems:
  • CentOS / RHEL 7.6 or above
  • CentOS / RHEL 8.0 or above

Instructions are located in the download .zip file