Mise à jour de 'dns/README.md'

dns/README.md

@@ -1,8 +1,48 @@
 # Private DNS installation
 
+## Contexte
+
+We want to deploy an internal DNS to serve private domain and that will be able to forward any other requests to another DNS.
+
+## Architecture
+
+We will use CoreDNS (not the cluster internal) to serve those requests.
+A etcd cluster will be deployed in statefullset, with PVC, as CoreDNS' backend.
+We finally deploy external-dns to handle DNS entry creation and suppression, in Service or Ingress rules.
+
+## Deploy
+
+Pretty straitforward using manifests from 01\* to 04\*.
+The CoreDNS configuration is in 04-coredns.yaml :
+
+```
+data:
+  Corefile: |
+    open-it.intra {
+        errors
+        health
+        log
+        etcd {
+           endpoint http://etcd-dns:2379
+        }
+        cache 30
+        prometheus 0.0.0.0:9153
+    }
+    
+    . {
+        forward . 192.168.5.1
+        cache
+    }
+```
 
 
 
+## Testing 
+
+We will test by deploying a service type **LoadBalancer** with the annotation :
+**external-dns.alpha.kubernetes.io/hostname: "<url|fqdn>"**
+
+Let's try with that Service :
 
 ```
     apiVersion: v1
@@ -20,3 +60,23 @@
         app: nginx
       type: LoadBalancer
 ```
+
+First, let's retrieve DNS IP :
+
+```
+kubectl -n dns get svc coredns
+NAME      TYPE           CLUSTER-IP     EXTERNAL-IP     PORT(S)        AGE
+coredns   LoadBalancer   10.97.35.253   192.168.5.201   53:32585/UDP   1d
+```
+
+We can now try DNS resolution
+
+```
+$ dig @192.168.5.201 nginx.open-it.intra -short
+ ```
+
+or
+
+```
+nslookup nginx.open-it.intra 192.168.5.201
+```