Cannot install the vCenter Server agent(HA) service. Unknown installer error

It had been a while since I have installed a non HCI VMware cluster. After installing the ESXi hosts, the updates and multipath software were installed. The storage team has made the datastores available. Nothing special. After installation, the host has been taken out of maintenance mode. Then there was an error “Error: “Cannot install the vCenter Server agent service. Unknown installer error“. See VMware KB #2083945 and VMware KB #2056299.

I have followed all standard procedures to resolve HA errors:

  • Right click the affected host. Reconfigure for vSphere HA
  • Reconfigure HA on a cluster level.  Turn Off vSphere HA and  Turn ON vSphere HA
  • Disconnect and reconnect the affected host

After performing the above options, the issue was still unsolved. Next I wanted to know if the HA (fdm) agent is installed or not. I ssh to the host and ran the following command:

Esxcli software vib list | grep fdm

The output was empty. I realized that the HA agent was not installed. In VMware KB #2056299 is written about a vib dependency. That made me realize that besides the VMware updates also multipath software was installed, Dell EMC PowerPath/VE. This turned me out to the right direction to solve the problem.


  • Ssh to the affected host(in maintenance mode)
  • Esxcli software vib list or Esxcli software vib list | grep power. The results are three vibs: powerpath.plugin.esx, powerpath.cim.esx and powerpath.lib.esx
  • Uninstall the three vibs running the following command: esxcli software vib remove –vibname=powerpath.plugin.esx –vibname=powerpath.cim.esx –vibname=powerpath.lib.esx
  • Reboot the host
  • Esxcli software vib list | grep power The output shlould be empty.
  • Leaving maintenance mode. The HA agent is now installing. After the HA agent is installed enter maintenance mode again
  • Esxcli software vib list | grep fdm The output should be similar like: vmware-fdm VMware VMwareCertified 2021-02-16
  • Reinstall Dell EMC PowerPath/VE. Installing the same version PowerPath/VE gave a VUM error even after restarting the host. To resolve this error I’ve installed a newer version of PowerPath/VE. This version was installed succesful.
  • Leaving maintenance mode

In my case the PowerPath/VE vibs dependecies were causing the issue. Another dependency can also cause this problem. I am aware that looking for the right dependence can be a difficult job. I hope I have at least been able to help you start the search in the right direction.

November 2022. An update about this issue can be read here.

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