When you enable periodic time synchronization, VMware Tools sets the time of the guest operating system to be the same as the time of the host.

After time synchronization occurs, VMware Tools checks once every minute to determine whether the clocks on the guest and host operating systems still match. If not, the clock on the guest operating system is synchronized to match the clock on the host.

If the clock on the guest operating system falls behind the clock on the host, VMware Tools moves the clock on the guest forward to match the clock on the host. If the clock on the guest operating system is ahead of the clock on the host, VMware Tools causes the clock on the guest to run more slowly until the clocks are synchronized.

Native time synchronization software, such as Network Time Protocol (NTP) for Linux and the Mac OS X, or Microsoft Windows Time Service (Win32Time) for Windows, is typically more accurate than VMware Tools periodic time synchronization. Use only one form of periodic time synchronization in your guests. If you are using native time synchronization software, disable VMware Tools periodic time synchronization.

Regardless of whether you turn on VMware Tools periodic time synchronization, time synchronization occurs after certain operations:

  • When you start the VMware Tools daemon, such as during a reboot or power on operation
  • When you resume a virtual machine from a suspend operation
  • After you revert to a snapshot
  • After you shrink a disk

When the operating system starts or restarts, and when you first turn on periodic time synchronization, if the time.synchronize.tools.startup.backward parameter is not enabled in the .vmx file, the guest clock is set to forward. For other events, synchronization is forward in time.

To disable time synchronization completely, you must edit the configuration file (.vmx file) of the virtual machine and set several synchronization properties to FALSE.

Prerequisites

  • Disable other periodic time synchronization mechanisms. For example, some guests might have NTP or Win32Time clock synchronization turned on by default.
  • If you plan to script the commands used in this procedure and need to know what the exit codes are, see Exit Codes for the VMware Tools Configuration Utility.
Note: Mac OS X guest operating systems use NTP and do not become out of sync with the host. For Mac OS X guest operating systems, there is no need to turn on VMware Tools time synchronization.

Procedure

  1. Open a command prompt or terminal in the guest operating system.
  2. Change to the VMware Tools installation directory.
    Operating System Default Path
    Windows C:\Program Files\VMware\VMware Tools
    Linux and Solaris /usr/sbin
    FreeBSD /usr/local/sbin
    Mac OS X /Library/Application Support/VMware Tools
  3. Type the command to determine whether time synchronization is enabled. 
    utility-name timesync status

    For utility-name use the guest-specific program name.

    Operating System Program Name
    Windows VMwareToolboxCmd.exe
    Linux, Solaris, and FreeBSD vmware-toolbox-cmd
    MAC OS X vmware-tools-cli
  4. Type the command to enable or disable periodic time synchronization. 
    utility-name timesync subcommand

    For subcommand, use enable or disable.

Results

The VMware Tools service enables or disables periodic time synchronization, as you specified. Disabling periodic time synchronization does not disable all VMware Tools time synchronization.

What to do next

If you need to keep a fictitious time in a virtual machine, such that the clock in the guest operating system is never synchronized with that on the host, disable time synchronization completely for the guest operating system.