What are the meanings of different DNS configuration options?

Can you adapt a DNS configuration to be used by the workload on the cluster (CoreDNS configuration)?

Yes, you can. Information on that can be found in Custom DNS Configuration.

How to use custom domain names using a DNS provider?

Creating custom domain names for the Gardener infrastructure DNS records using DNSRecords resources

With DNSRecords internal and external domain names of the kube-apiserver are set, as well as the deprecated ingress domain name and an “owner” DNS record for the owning seed.

For this purpose, you need either a provider extension supporting the needed resource kind DNSRecord/<provider-type> or a special extension.

All main providers support their respective IaaS specific DNS servers:

• AWS => DNSRecord/aws-route53
• GCP => DNSRecord/google-cloudns
• Azure => DNSRecord/azure-dns
• Openstack => DNSRecord/openstack-designate
• AliCloud => DNSRecord/alicloud-dns

For Cloudflare there is a community extension existing.

For other providers like Netlify and infoblox there is currently no known supporting extension, however, they are supported for shoot-dns-service.

Creating domain names for cluster resources like ingress or services with services of type Loadbalancers and for TLS certificates

For this purpose, the shoot-dns-service extension is used (DNSProvider and DNSEntry resources).

You can read more on it in these documents:

• Deployment of the Shoot DNS Service Extension
• Request DNS Names in Shoot Clusters
• DNS Providers
• Gardener DNS Management for Shoots
• Request X.509 Certificates
• Gardener Certificate Management