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One of the new features of vSphere 5.1 was upgrade procedure of the VMware Tools on Windows VMs: when you upgrade them the first time to version 5.1 (the right version number it’s 9.x), other upgrade will not require any reboot of your Windows system.

For Linux VMs there is no need to reboot the system (but I suggest in order to be sure that the kernel modules are loaded proprerly), and now also Windows VMs could have a zero downtime upgrade. But it’s really true?

Honestly I found that on some VMs the automatic upgrade procedure of VMware Tools will also take an unattended reboot of your VM, like in this case:


Usually it appen on a virtual vCenter Server (if also a DB is hosted in the same VM). But not only. And it’s not so funny!

To determining if a VMware Tools upgrade requires a reboot of a Windows guest operating system you can use the VMware KB 2015163. Another good source of information if this post: Clarification on (Zero-Down Time) VMware Tools Upgrade in vSphere 5.1.

Considering that this check takes time, I always suggest to plan your VMware Tools upgrade in extra-time (remember that you can use VUM to schedule and automate this task) and maybe could also be the right moment to do other OS/app related upgrade.

Note that the same issue apply also to VMware Tools 5.5.


Virtualization, Cloud and Storage Architect. Tech Field delegate. VMUG IT Co-Founder and board member. VMware VMTN Moderator and vExpert 2010-24. Dell TechCenter Rockstar 2014-15. Microsoft MVP 2014-16. Veeam Vanguard 2015-23. Nutanix NTC 2014-20. Several certifications including: VCDX-DCV, VCP-DCV/DT/Cloud, VCAP-DCA/DCD/CIA/CID/DTA/DTD, MCSA, MCSE, MCITP, CCA, NPP.