Ubuntu guest with VMware tools may have guest time over corrected if ntpdate script is running

Products

• VMware vSphere ESX 7.x

Issue/Introduction

Ubuntu Guest OS time is ahead of the current time after a reset or reboot

Environment

• VMware vSphere 7.0.3
• Ubuntu guests 18.04/16.04/14.04

Cause

• This issue occurs due to a race condition between VMware tools and /etc/network/if-up.d/ntpdate script if they attempt to correct the guest operating system time at the same time.

Example Scenario:

• Change the guest operating system time backward by X mins and sync to hardware clock
• Reboot/Reset the guest operating system
• After the reset, VMware tools will correct the guest operating system time with an offset of +X mins. At almost the same time, /etc/network/if-up.d/ntpdate script may also correct time with offset of +X mins.
• Guest operating system time is now corrected twice and will have current time + X mins.

This is not likely to happen but it is possible.

Resolution

To prevent the issue from occurring modify the file name from /etc/network/if-up.d/ntpdate to /etc/network/if-up.d/ntpdate.disabled

Note: No service restart is required for the changes to take effect. During the next reset or reboot, ntpdate will not act and only VMware tools will do the time correction.