[pt-br] Translating page: Customizing DNS Service

Done:
   + Introduction
   + CoreDNS

TODO:
   - CoreDNS ConfigMap options
   - Configuration of Stub-domain and upstream nameserver using CoreDNS
   - Example

kubernetes#13939

content/pt-br/docs/tasks/administer-cluster/dns-custom-nameservers.md

@@ -0,0 +1,187 @@
+---
+reviewers:
+- bowei
+- zihongz
+title: Customizing DNS Service
+content_type: task
+min-kubernetes-server-version: v1.12
+---
+
+<!-- overview -->
+Essa pagina explica como configurar o seu DNS
+{{< glossary_tooltip text="Pod(s)" term_id="pod" >}} e personalizar o processo de resolução de DNS no seu cluster.
+
+## {{% heading "prerequisites" %}}
+
+{{< include "task-tutorial-prereqs.md" >}}
+
+Seu cluster deve estar executando o complemento CoreDNS.
+
+{{% version-check %}}
+
+<!-- steps -->
+
+## Introdução
+
+DNS é um serviço integrado do Kubernetes que é integrado automaticamente usando o _gerenciador de complementos_ [cluster add-on](http://releases.k8s.io/master/cluster/addons/README.md).
+
+{{< note >}}
+O Serviço CoreDNS é chamado de `kube-dns` no campo `metadata.name`.
+O objetivo é garantir maior interoperabilidade com cargas de trabalho que dependiam do nome de serviço legado `kube-dns` para resolver endereços internos ao cluster.
+Usando o serviço chamado `kube-dns` abstrai o detalhe de implementação de qual provedor de DNS está sendo executado por trás desse nome comum.
+{{< /note >}}
+
+Se você estiver executando o CoreDNS como um Deployment, ele geralmente será exposto como um Serviço do Kubernetes com o endereço de IP estático.
+O kubelet passa informações de resolução de DNS para cada contêiner com a flag `--cluster-dns=<dns-service-ip>`.
+
+Os nomes DNS também precisam de domínios. Você configura o domínio local no kubelet com a flag `--cluster-domain=<default-local-domain>`.
+
+O servidor DNS suporta pesquisas de encaminhamento (registros A e AAAA), pesquisas de porta (registros SRV), pesquisas de endereço de IP reverso (registros PTR) e muito mais. Para mais informações, veja [DNS para Serviços e Pods](/docs/concepts/services-networking/dns-pod-service/).
+
+Se a `dnsPolicy` de um Pod estiver definida como `default`, ele herda a configuração de resolução de nome do nó em que o Pod é executado. A resolução de DNS do Pod deve se comportar da mesma forma que o nó.
+Veja [Problemas conhecidos](/docs/tasks/administer-cluster/dns-debugging-resolution/#known-issues)..
+
+Se você não quiser isso, ou se quiser uma configuração de DNS diferente para os pods, pode usar a flag `--resolv-conf` do kubelet. Defina essa flag como "" para impedir que os Pods herdem a configuração do DNS. Defina-a como um caminho de arquivo válido para especificar um arquivo diferente de `/etc/resolv.conf` para a herança de DNS.
+
+## CoreDNS
+
+CoreDNS é um servidor oficial de DNS de propósito geral que pode atuar como DNS do cluster,
+cumprindo com as [especificações DNS](https://github.com/kubernetes/dns/blob/master/docs/specification.md).
+
+### CoreDNS ConfigMap options
+
+CoreDNS is a DNS server that is modular and pluggable, with plugins adding new functionalities.
+The CoreDNS server can be configured by maintaining a [Corefile](https://coredns.io/2017/07/23/corefile-explained/),
+which is the CoreDNS configuration file. As a cluster administrator, you can modify the
+{{< glossary_tooltip text="ConfigMap" term_id="configmap" >}} for the CoreDNS Corefile to
+change how DNS service discovery behaves for that cluster.
+
+In Kubernetes, CoreDNS is installed with the following default Corefile configuration:
+
+```yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: coredns
+  namespace: kube-system
+data:
+  Corefile: |
+    .:53 {
+        errors
+        health {
+            lameduck 5s
+        }
+        ready
+        kubernetes cluster.local in-addr.arpa ip6.arpa {
+            pods insecure
+            fallthrough in-addr.arpa ip6.arpa
+            ttl 30
+        }
+        prometheus :9153
+        forward . /etc/resolv.conf
+        cache 30
+        loop
+        reload
+        loadbalance
+    }
+```
+
+The Corefile configuration includes the following [plugins](https://coredns.io/plugins/) of CoreDNS:
+
+* [errors](https://coredns.io/plugins/errors/): Errors are logged to stdout.
+* [health](https://coredns.io/plugins/health/): Health of CoreDNS is reported to
+  `http://localhost:8080/health`. In this extended syntax `lameduck` will make theuprocess
+  unhealthy then wait for 5 seconds before the process is shut down.
+* [ready](https://coredns.io/plugins/ready/): An HTTP endpoint on port 8181 will return 200 OK,
+  when all plugins that are able to signal readiness have done so.
+* [kubernetes](https://coredns.io/plugins/kubernetes/): CoreDNS will reply to DNS queries
+  based on IP of the Services and Pods. You can find [more details](https://coredns.io/plugins/kubernetes/)
+  about this plugin on the CoreDNS website.
+  - `ttl` allows you to set a custom TTL for responses. The default is 5 seconds.
+    The minimum TTL allowed is 0 seconds, and the maximum is capped at 3600 seconds.
+    Setting TTL to 0 will prevent records from being cached.  
+  - The `pods insecure` option is provided for backward compatibility with `kube-dns`.
+  - You can use the `pods verified` option, which returns an A record only if there exists a pod
+    in the same namespace with a matching IP.
+  - The `pods disabled` option can be used if you don't use pod records.
+* [prometheus](https://coredns.io/plugins/metrics/): Metrics of CoreDNS are available at
+  `http://localhost:9153/metrics` in the [Prometheus](https://prometheus.io/) format
+  (also known as OpenMetrics).
+* [forward](https://coredns.io/plugins/forward/): Any queries that are not within the Kubernetes
+  cluster domain are forwarded to predefined resolvers (/etc/resolv.conf).
+* [cache](https://coredns.io/plugins/cache/): This enables a frontend cache.
+* [loop](https://coredns.io/plugins/loop/): Detects simple forwarding loops and
+  halts the CoreDNS process if a loop is found.
+* [reload](https://coredns.io/plugins/reload): Allows automatic reload of a changed Corefile.
+  After you edit the ConfigMap configuration, allow two minutes for your changes to take effect.
+* [loadbalance](https://coredns.io/plugins/loadbalance): This is a round-robin DNS loadbalancer
+  that randomizes the order of A, AAAA, and MX records in the answer.
+
+You can modify the default CoreDNS behavior by modifying the ConfigMap.
+
+### Configuration of Stub-domain and upstream nameserver using CoreDNS
+
+CoreDNS has the ability to configure stub-domains and upstream nameservers
+using the [forward plugin](https://coredns.io/plugins/forward/).
+
+#### Example
+
+If a cluster operator has a [Consul](https://www.consul.io/) domain server located at "10.150.0.1",
+and all Consul names have the suffix ".consul.local". To configure it in CoreDNS,
+the cluster administrator creates the following stanza in the CoreDNS ConfigMap.
+
+```
+consul.local:53 {
+    errors
+    cache 30
+    forward . 10.150.0.1
+}
+```
+
+To explicitly force all non-cluster DNS lookups to go through a specific nameserver at 172.16.0.1,
+point the `forward` to the nameserver instead of `/etc/resolv.conf`
+
+```
+forward .  172.16.0.1
+```
+
+The final ConfigMap along with the default `Corefile` configuration looks like:
+
+```yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: coredns
+  namespace: kube-system
+data:
+  Corefile: |
+    .:53 {
+        errors
+        health
+        kubernetes cluster.local in-addr.arpa ip6.arpa {
+           pods insecure
+           fallthrough in-addr.arpa ip6.arpa
+        }
+        prometheus :9153
+        forward . 172.16.0.1
+        cache 30
+        loop
+        reload
+        loadbalance
+    }
+    consul.local:53 {
+        errors
+        cache 30
+        forward . 10.150.0.1
+    }
+```
+
+{{< note >}}
+CoreDNS does not support FQDNs for stub-domains and nameservers (eg: "ns.foo.com").
+During translation, all FQDN nameservers will be omitted from the CoreDNS config.
+{{< /note >}}
+
+## {{% heading "whatsnext" %}}
+
+- Read [Debugging DNS Resolution](/docs/tasks/administer-cluster/dns-debugging-resolution/)
+