Before upgrading to vCenter Server Appliance 6.5, you must prepare your ESXi hosts.


To upgrade vCenter Server Appliance, your ESXi hosts must meet the requirements for upgrade.

  • ESXi hosts must be at version 5.5 or later. Read and follow all best practices when upgrading your hosts to ESXi 5.5.
  • Your target host must be running ESXi 5.5 or later.
  • Your source and target ESXi hosts must not be in lockdown or maintenance mode and not part of fully automated DRS clusters.


  1. To keep your current SSL certificates, back up the SSL certificates that are on the vCenter Server Appliance system before you upgrade to vCenter Server Appliance 6.5.
    The default location of the SSL certificates is %allusersprofile%\Application Data\VMware\VMware VirtualCenter.
  2. If you have Custom or Thumbprint certificates, see Host Upgrades and Certificates to determine your preparatory steps.
  3. If you have vSphere HA clusters, SSL certificate checking must be enabled.
    If certificate checking is not enabled when you upgrade, vSphere HA fails to configure on the hosts.
    1. Select the vCenter Server Appliance instance in the inventory panel.
    2. Select the Manage tab and the General subtab.
    3. Verify that the SSL settings field is set to vCenter Server requires verified host SSL certificates.


Your ESXi hosts are ready for vCenter Server Appliance upgrade.