Without it, since kubefirst don't generate custom signed certificate for kubelet, metrics server will generate the 'failed to verify certificate: x509: cannot validate certificate for XXX.XXX.X.X because it doesn't contain any IP SANs' error and won't work at all.
Without it, since kubefirst don't generate custom signed certificate for kubelet, metrics server will generate the 'failed to verify certificate: x509: cannot validate certificate for XXX.XXX.X.X because it doesn't contain any IP SANs' error and won't work at all.