vSphere HA fails with error "Cannot find vSphere HA master agent" due to missing fdm.conf

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

• vSphere High Availability (HA) fails to initialize or operate correctly on ESXi hosts. The vSphere Client displays the following error: Cannot find vSphere HA master agent

• HA status for the host shows as "Inbound" or "Uninitialized."

• The Fault Domain Manager (FDM) agent fails to start or elect a master.

• Manual inspection of the host confirms the file /etc/opt/vmware/fdm/Fdm.cfg is missing or was accidentally deleted.

Environment

• ESXi 8.x
• vCenter 8.x

Cause

Removal of the fdm.conf configuration file on the ESXi hosts, which is required for the FDM agent to function.

Resolution

Recreate the missing configuration file by exporting a generic version from a working host in the same environment and importing it into the affected host(s).

1. Log into a working ESXi host in the same cluster via SSH.

2. Locate the generic FDM configuration file at /etc/opt/vmware/fdm/Fdm.cfg.

3. Copy the content of the file. A standard configuration includes:

<!-- VALUES IN THIS FILE ARE PROCESSED FOR CONFIGSTORE -->
<config>

  <fdm>
    <memoryCheckerTimeInSecs>0</memoryCheckerTimeInSecs>
    <memReservationMB>200</memReservationMB>
  </fdm>

  <alert>
    <log>
      <enabled>false</enabled>
    </log>
  </alert>

  <log>
    <level>verbose</level>
    <outputToFiles>false</outputToFiles>
    <maxFileSize>0</maxFileSize>
    <maxFileNum>0</maxFileNum>
    <memoryLevel>trivia</memoryLevel>
    <outputToConsole>false</outputToConsole>
    <!-- If true, logs to syslog -->
    <outputToSyslog>true</outputToSyslog>
    <!-- syslog configuration.  Only used if outputToSyslog is true. -->
    <syslog>
      <!-- syslog identifier to use when logging -->
      <ident>Fdm</ident>
      <!-- syslog facility to use when logging -->
      <facility>local4</facility>
      <!-- The section header contents are placed in this file at startup.
           When vmsyslogd rotates the fdm log file, it logs the content of this
           file to syslog. This is being done so that we don't lose context on log
           rotations.
           IMPORTANT: Value needs to match that in onrotate entry in
           vmsyslog.conf.d/fdm.conf
       -->
      <logHeaderFile>/var/run/vmware/fdmLogHeader.txt</logHeaderFile>
    </syslog>
  </log>
  <level id="SoapAdapter.HTTPService">
     <logName>SoapAdapter.HTTPService</logName>
     <logLevel>info</logLevel>
  </level>
  <level id="SoapAdapter">
     <logName>SoapAdapter</logName>
     <logLevel>info</logLevel>
  </level>

  <workingDir>/</workingDir>

  <vmacore>
    <ssl>
      <doVersionCheck>false</doVersionCheck>
      <!-- allowed SSL/TLS protocol versions -->
      <!-- <protocols>tls1.0,tls1.1,tls1.2</protocols> -->
    </ssl>
    <!-- @todo determine the appropriate limit of vmacore threads -->
    <threadPool>
      <TaskMax>4</TaskMax>
      <IoMax>9</IoMax>
    </threadPool>
    <http>
      <!-- @todo determine the appropriate throttling limit of vmacore threads -->
      <defaultClientPoolConnectionsPerServer>
        100
      </defaultClientPoolConnectionsPerServer>
    </http>
  </vmacore>

  <task>
    <!-- @todo determine the appropriate limit of vpx root LROs -->
    <totalThreads>28</totalThreads>
  </task>

  <trace>
    <mutex>
      <toleranceThresholdMS>100</toleranceThresholdMS>
    </mutex>
    <vmomi>
      <calls>false</calls>
    </vmomi>
  </trace>

</config>

4. Log into the affected ESXi host via SSH.

5. Create the file /etc/opt/vmware/fdm/Fdm.cfg using a text editor (e.g., vi) and paste the content above.

6. Save the file.

7. Right-click the host in vCenter and select Reconfigure for vSphere HA.