Hi all.
Today i had to reinstall some ESXi 5.5 hosts as we were upgrading to SSD disks, in order to have more performance on the Citrix environment we are hosting.

Before i powered off the server, i saved the configuration to use for easy reconfiguration with the following command from powercli:

Get-VMHostFirmware -VMHost xxx-hostname-xxx -BackupConfiguration -DestinationPath C:\HostBackups\

Now i got a xxx.tgz file containing the full configuration of the original ESXi host, ready for importing back when the reinstall is done.

When the server was installed on the new disks, i connected directly to the reinstalled server by its IP address,  put the server in maintenance mode and imported the configuration backup with these commands from powercli:

Set-VMHost -State Maintenance

 

Set-VMHostFirmware -VMHost xxx-hostname-xxx -Restore -SourcePath c:\HostBackups\xxx.tgz -HostUser user -HostPassword password

Because of the new disks i got an error regarding my vmkcore vmkdumpfile that was missing. I was able to list the partition table, which showed that i had two different dump partitions, but none of them were configured for use.
To get it fixed i had to unconfigure the existing coredump partition with this command from the ESXi shell:

esxcli system coredump partition set -u

And then reconfigure the partition with this command, also from the ESXi shell:

esxcli system coredump partition set –enable true –smart

This command will let the system choose which partition to use for the coredumps. The system will now use the choosen partition, no reboot needed.