Custom private domain name in kubernetes cluster

calendar Sep 3, 2020 ·  · kubernetes Coredons  ·
: linkedin copy

We use default service domain name ${servicename}.${namespace}.svc.cluster.localin kubernetes cluster, however the custom private domain name in private k8s networks frequently used. we can use coredns component reparse the private domain name to default CNAME.

change coredns configmap add custom domain name config to yaml

kubectl edit cm coredns -n kube-system

 1data:
 2    Corefile: |
 3      .:53 {
 4          errors
 5          health {
 6             lameduck 5s
 7          }
 8          ready
 9          kubernetes cluster.local in-addr.arpa ip6.arpa {
10             pods insecure
11             fallthrough in-addr.arpa ip6.arpa
12             ttl 30
13          }
14          file /etc/coredns/uat-env.db uat-env.com
15          prometheus :9153
16          forward . /etc/resolv.conf
17          cache 30
18          loop
19          reload
20          loadbalance
21      }      
22    uat-env.db: >-
23      uat-env.com.      IN      SOA     ns.dns.cluster.local. 
24      hostmaster.cluster.local. 1592362202 7200 1800 86400 30
25
26      uat-env.com.      IN    NS   
27      kube-dns.kube-system.svc.cluster.local.
28
29      db.uat-env.com.  IN  CNAME  
30      mysql.db.svc.cluster.local.
31
32      private-services.uat-env.com.  IN CNAME
33      internal-gateway.default.svc.cluster.local.
...
yaml

add file /etc/coredns/uat-env.db uat-env.com line to Corefile section add new section uat-env.db and add relative recordset

kubectl edit deployment coredns -n kube-system under config-volume section in volumes section add an item, looks like this

1items:
2    - key: Corefile
3      path: Corefile
4    - key: uat-env.db
5      path: uat-env.db
yaml

that’s all, enjoy it.

1# test it
2dig db.uat-env.com
3curl http://private-services.uat-env.com
bash