vSphere Lifecycle Manager (vLCM) Compliance Scan Fails with "Unknown installer error"

Products

• VMware vSphere ESXi

Issue/Introduction

• When attempting to upgrade ESXi hosts from version 7.0 U3 to 8.0 U3 via VMware vSphere Lifecycle Manager (vLCM), the compliance check or remediation process fails.
• The vSphere Client displays a generic error message: 

  
Cannot install the vCenter Server agent service. "Unknown installer error"

Environment

VMware ESXi
VMware vCenter

Cause

The issue is typically caused by a combination of the following factors:

1. Network Connectivity: Port TCP 80 (HTTP) is blocked between the vCenter Server and the target ESXi hosts. vLCM requires Port 80 for metadata exchange and VIB downloads during the remediation process.
   • Login to the ESXi host putty session as user root
   • Run the command nc -vz <vCenter-IP-Address> 80
   • Similarly, login to the vCenter SSH session with root login and switch to the Linux shell using shell command.
   • Run the command curl -kv telnet://<Esxi-host-ip-address>:80
2. If any of the above command shows error, then verify the HTTPs port 80 setting on the ESXi host internal firewall.
   
   
3. Internal Firewall Configuration: The ESXi host's internal firewall has the HTTP client or related services disabled, preventing the return path for vCenter communication.

Resolution

To resolve this issue, perform the following troubleshooting and remediation steps:

1. Enable Required Network Ports

Ensure that traffic is permitted from the vCenter Server appliance to the ESXi hosts on the following ports:

• TCP 80: Required for vLCM/VUM agent communication.
• TCP 9084: Required for vSphere Lifecycle Manager to download metadata and payloads.

2. Configure ESXi Host Firewall

If network firewalls are open but connectivity still fails, enable the service on the ESXi host:

1. Log in to the vSphere Client.
2. Select the ESXi host and navigate to Configure > System > Firewall.
3. Click Edit and locate the HttpClient or Port 80 service.
4. Ensure it is enabled and the daemon is started.

Additional Information

 Post-Upgrade VIB Synchronization (NSX Environments only)

If the environment uses NSX, the upgraded host may show a VIB mismatch:

1. Navigate to the NSX Manager UI.
2. Go to System > Fabric > Nodes > Host Transport Nodes.
3. Select the affected host and click Resolve to push the 8.0-compatible VIBs.
4. Refer to the articles for more details :- KB401684