In the VMware Tools control panel, the time synchronization checkbox is unselected, but you may experience these symptoms:
VMware Tools can perform two types of time corrections:
VMware Tools does not set time backwards (when guest time is ahead of the host), except once when periodic time synchronization is turned on.
In vSphere 7.0 Update 1 and later version, the VMware Tools menu in the Edit Settings Wizard for a virtual machine provides two check-boxes, which allow to enable or disable one-off time synchronization and periodic time synchronization:
To disable periodic time synchronization in a VM, launch vSphere Client, go to Edit Settings → VM Options → VMware Tools → Synchronize Time with Host, and deselect the checkbox Synchronize time periodically.
The vmx option for this setting is tools.syncTime and its value can be "TRUE" when periodic time sync is enabled, or "FALSE" when periodic time sync is disabled.
To disable one-off time synchronization in a VM, launch vSphere Client, go to Edit Settings → VM Options → VMware Tools → Synchronize Time with Host, and deselect the checkbox Synchronize at startup and resume (recommended). Disabling one-off time synchronization as described will also automatically force disable periodic time synchronization.
This setting is managed with the vmx option time.synchronize.allow. By default, when one-off time synchronization is enabled, the option has the value "TRUE", but is not contained in the vmx configuration file. When one-off time synchronization is however disabled, you can find this option in the vmx configuration file with the value "FALSE".
VMware Workstation, Fusion, and vSphere prior to version 7.01 U1 provide a single checkbox in a VM's VMware Tools control panel, which enables or disables periodic time synchronization only.
To disable periodic time synchronization in a VM, launch vSphere Client, go to Edit Settings → VM Options → VMware Tools → Time, and deselect the checkbox Synchronize guest time with host
To disable one-off time synchronization in a VM, you must set the following advanced configuration settings.
time.synchronize.continue = "FALSE" time.synchronize.restore = "FALSE" time.synchronize.resume.disk = "FALSE" time.synchronize.shrink = "FALSE" time.synchronize.tools.startup = "FALSE" time.synchronize.tools.enable = "FALSE" time.synchronize.resume.host = "FALSE" |
VM advanced settings can be modified using vSphere client or by editing the VM's .vmx file. See the following articles for more information:
These advanced VM settings do not take effect until the VM (or VMware Tools running within it) is restarted.
The steps described above for disabling time synchronization apply ONLY to the behavior and impact of the time synchronization feature of VMware Tools running inside a VM. The guest operating system in the VM may rely on additional sources of wall clock time information for general timekeeping. Guest OSes typically read virtual CMOS/RTC clock to bootstrap system time during start up. On VMware, time on the virtual CMOS/RTC clock is derived from the host's time, at an offset established at first power-on (or when the guest OS writes back to CMOS). If subsequently, the host clock is modified to an incorrect value, or if the VM is migrated to a host with incorrect UTC time, the guest will derive a corresponding incorrect notion of wall time at start up. Disabling VMware Tools time synchronization with the host does not avoid this scenario. Therefore, it is important to always configure all ESXi hosts to synchronize time to one or more external, reliable sources of time.
See also Timekeeping in VMware Virtual Machines.