instruction: Create a Dockerfile for networking
output: ```dockerfile
  from the specified DNS policy.
  Duplicate entries are removed.
  
  The following is an example Pod with custom DNS settings:
  
  service/networking/custom-dns.yaml
  
  apiVersion: v1
  kind: Pod
  metadata:
   namespace: default
   name: dns-example
  spec:
   containers:
   - name: test
   image: nginx
   dnsPolicy: "None"
   dnsConfig:
   nameservers:
   - 192.0.2.1 # this is an example
   searches:
   - ns1.svc.cluster-domain.example
   - my.dns.search.suffix
   options:
   - name: ndots
   value: "2"
   - name: edns0
  
  When the Pod above is created, the container test gets the following contents
  in its /etc/resolv.conf file:
  nameserver 192.0.2.1
  search ns1.svc.cluster-domain.example my.dns.search.suffix
  options ndots:2 edns0
  For IPv6 setup, search path and name server should be set up like this:
  kubectl exec -it dns-example -- cat /etc/resolv.conf
  The output is similar to this:
  nameserver 2001:db8:30::a
  search default.svc.cluster-domain.example svc.cluster-domain.example cluster-domain.example
  options ndots:5
  DNS search domain list limits
  
  FEATURE STATE: Kubernetes 1.28 [stable]
  
  Kubernetes itself does not limit the DNS Config until the length of the search
  domain list exceeds 32 or the total length of all search domains exceeds 2048.
  This limit applies to the node's resolver configuration file, the Pod's DNS
  Config, and the merged DNS Config respectively.
  Note:Some container runtimes of earlier versions may have their own restrictions on
  the number of DNS search domains. Depending on the container runtime
  environment, the pods with a large number of DNS search domains may get stuck in
  the pending state.
  It is known that containerd v1.5.5 or earlier and CRI-O v1.21 or earlier have
  this problem.
  
  DNS resolution on Windows nodes
  
  ClusterFirstWithHostNet is not supported for Pods that run on Windows nodes.
  Windows treats all names with a . as a FQDN and skips FQDN resolution.
  On Windows, there are multiple DNS resolvers that can be used. As these come with
  slightly different behaviors, using the
  Resolve-DNSName
  powershell cmdlet for name query resolutions is recommended.
  On Linux, you have a DNS suffix list, which is used after resolution of a name as fully
  qualified has failed.
  On Windows, you can only have 1 DNS suffix, which is the DNS suffix associated with that
  Pod's namespace (example: mydns.svc.cluster.local). Windows can resolve FQDNs, Services,
  or network name which can be resolved with this single suffix. For example, a Pod spawned
  in the default namespace, will have the DNS suffix default.svc.cluster.local.
  Inside a Windows Pod, you can resolve both kubernetes.default.svc.cluster.local
  and kubernetes, but not the partially qualified names (kubernetes.default or
  kubernetes.default.svc).
  
  What's next
  For guidance on administering DNS configurations, check
  Configure DNS Service
  
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   Last modified January 29, 2024 at 12:52 AM PST: updated the link for admission webhook controller (a3b714cbfc)
  
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  Namespaces of Services
  DNS Records
  
  Services
  
  A/AAAA records
  SRV records
  
  Pods
  
  A/AAAA records
  Pod's hostname and subdomain fields
  Pod's setHostnameAsFQDN field
  Pod's DNS Policy
  Pod's DNS Config
  
  DNS search domain list limits
  DNS resolution on Windows nodes
  What's next
  
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  © 2025 The Kubernetes Authors | Documentation Distributed under CC BY 4.0
  
  ICP license: 京ICP备17074266号-3
  ```