When an ESXi host encounters a critical error and halts with a purple diagnostic screen, it attempts to dump diagnostic information to disk or via the network. If these attempts are unsuccessful due to configuration errors or critical failures, not much troubleshooting information is available.
The purple diagnostic screen contains messages similar to:
"Escape" for local debugger.
Press Escape to enter local debugger.
In such cases, you can use the ESXi local debugger to review the VMkernel logs to determine the cause of outage.
vmkernel debugger (h for help).
vmkernel debugger (h for help)
.