Note: Ensure the VMs are Migrated to some other Host and place the Host in Maintenance mode as it might get disconnected from vCenter while replacing the Custom Certs to VMCA.
Take SSH Access to ESXi Host
Validate the existing certificates located in /etc/vmware/ssl.
cat /etc/vmware/ssl/
openssl x509 -in /etc/vmware/ssl/rui.crt -text -noout | grep Issuer
To Remove the Custom Certificates, delete the existing custom certificate and key
rm -f /etc/vmware/ssl/rui.crt
rm -f /etc/vmware/ssl/rui.key
To Generate New Local Certificates, Use the ESXi utility to generate a fresh set of temporary certificates:
/sbin/generate-certificates
Restart Host Management Services,Restart hostd and vpxa to apply the new certificates and re-enable vCenter communication:
/etc/init.d/hostd restart
/etc/init.d/vpxa restart
The Host will be in a disconnected state on the vCenter now, Reconnect it.
Verify that the new certificate is successfully signed by the VMware Certificate Authority (VMCA):
openssl x509 -in /etc/vmware/ssl/rui.crt -text -noout | grep Issuer
Use the vCenter Server advanced settings to set the Certificate mode to vmca
Click Configure, and under Settings, click Advanced Settings.
Click Edit Settings.
Click the Filter icon in the Name column, and in the Filter box, enter vpxd.certmgmt to display only certificate management parameters.
Change the value of vpxd.certmgmt.mode to vmca
Note: Use VMware Certificate Authority (VMCA) to provision certificates of the ESXi hosts in your environment unless corporate policy requires that you use custom certificates. To use custom certificates with a different root CA, you can edit the vCenter Servervpxd.certmgmt.mode advanced option. After the change, the hosts are no longer automatically provisioned with VMCA certificates when you refresh the certificates, Refer to Change the Certificate Mode