CoreDNS访问

除了直接用cluster ip，以及上面说到的NodePort模式来访问Service，我们还可以用K8s的DNS来访问

# 我们前面装好的CoreDNS，来提供K8s集群的内部DNS访问
[root@master1 ~]# kubectl -n kube-system get deployment,pod|grep dns
deployment.apps/coredns                   1/1     1            1           6d16h
pod/coredns-5787695b7f-42754                  1/1     Running   0          2d18h
pod/node-local-dns-2k5jn                      1/1     Running   0          6d16h
pod/node-local-dns-5rkcg                      1/1     Running   0          6d16h
pod/node-local-dns-pwpb8                      1/1     Running   0          6d16h

# coredns是一个DNS服务器，每当有新的Service被创建的时候，coredns就会添加该Service的DNS记录，然后我们通过serviceName.namespaceName就可以来访问到对应的pod了，下面来演示下：
[root@master1 ~]#  kubectl run -it --rm busybox --image=busybox -- sh    # --rm代表等我退出这个pod后，它会被自动删除，当作一个临时pod在用
If you don't see a command prompt, try pressing enter.
/ # ping nginx.default
PING nginx.default (10.68.142.234): 56 data bytes
64 bytes from 10.68.142.234: seq=0 ttl=64 time=0.108 ms
64 bytes from 10.68.142.234: seq=1 ttl=64 time=0.199 ms
64 bytes from 10.68.142.234: seq=2 ttl=64 time=0.147 ms
^C
--- nginx.default ping statistics ---
7 packets transmitted, 7 packets received, 0% packet loss
round-trip min/avg/max = 0.108/0.143/0.199 ms
/ # wget nginx.default
Connecting to nginx.default (10.68.142.234:80)
saving to 'index.html'
index.html           100% |*****************************************************************************************************************************|   612  0:00:00 ETA
'index.html' saved
/ # cat index.html 
v11111