An ESXi host runs virtual machines inside a VMware vSphere environment. If a host stops responding, it cannot be managed in vCenter Server. Virtual machines may also show as greyed out. This creates risks for system stability and daily tasks.
Problem Statement
One ESXi host showed not responding in vCenter. The host was disconnected. Attempts to reconnect failed. Virtual machines on that host appeared unavailable in the interface.
Investigation
Checking Host Access: We tested access from vCenter Server and the vSphere Client. The host was reachable. Basic connectivity was working.
IP and DNS Verification: We confirmed the correct management IP address. DNS resolution also worked with both IP and FQDN.
Service Review: We checked system logs. The VPXA log showed errors linked to the HOSTD service. HOSTD was not running.
Role of HOSTD: The vmware-hostd service handles communication between VMkernel and ESXi. If it fails, the host disconnects from vCenter. Even direct management from vSphere Client will not work.
Troubleshooting Steps
Tried restarting HOSTD, but it failed repeatedly.
Checked system logs for hardware or memory errors. No issues found.
Inspected /etc/vmware/hostd/config.xml. The file was corrupt.
Restored the configuration file from a backup.
Restarted HOSTD. The service started correctly.
Resolution
The corrupt config.xml file was the cause. Replacing it allowed HOSTD to run again. The ESXi host reconnected to vCenter Server. Virtual machines were once again visible and manageable.
Outcome
The ESXi host returned to normal state.
Virtual machines became manageable in vCenter.
The issue was solved without downtime.
Best Practices
Always check network connectivity first.
Review VPXA and HOSTD logs for clear error details.
Keep backups of config files like hostd/config.xml.
Monitor services on ESXi hosts often.
Document the solution for faster recovery in future.
Conclusion
An ESXi host not responding is a serious problem in a VMware setup. In this case, the cause was a stopped HOSTD service due to a corrupt config file. Restoring the file fixed the problem.
A step-by-step approach helped locate the cause and restore services quickly. Regular monitoring and file backups reduce risks of this issue repeating.
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