kubernetes - 无法从K8S Pod内部解析DNS

Question

在dnsutils Pod中执行ping stackoverflow.com

/ # ping stackoverflow.com
ping: bad address 'stackoverflow.com'

从pod内部看， /etc/resolve.conf文件看起来不错

/ # cat /etc/resolv.conf 
nameserver 10.96.0.10
search weika.svc.cluster.local svc.cluster.local cluster.local
options ndots:5

10.96.0.10是kube-dns服务ip:

[root@test3 k8s]# kubectl -n kube-system get service
NAME                        TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)                     AGE
kube-dns                    ClusterIP   10.96.0.10      <none>        53/UDP,53/TCP,9153/TCP      75d

core dns

[root@test3 k8s]# kubectl -n kube-system get  pod -o wide | grep core
coredns-6557d7f7d6-5nkv7                             1/1     Running   0          10d   10.244.0.14    test3.weikayuninternal.com   <none>           <none>
coredns-6557d7f7d6-gtrgc                             1/1     Running   0          10d   10.244.0.13    test3.weikayuninternal.com   <none>           <none>

当我将nameserver ip更改为coredns ip时。解决DNS是可以的。

/ # cat /etc/resolv.conf 
nameserver 10.244.0.14
#nameserver 10.96.0.10
search weika.svc.cluster.local svc.cluster.local cluster.local
options ndots:5
/ # ping stackoverflow.com
PING stackoverflow.com (151.101.65.69): 56 data bytes
64 bytes from 151.101.65.69: seq=0 ttl=49 time=100.497 ms
64 bytes from 151.101.65.69: seq=1 ttl=49 time=101.014 ms
64 bytes from 151.101.65.69: seq=2 ttl=49 time=100.462 ms
64 bytes from 151.101.65.69: seq=3 ttl=49 time=101.465 ms
64 bytes from 151.101.65.69: seq=4 ttl=49 time=100.318 ms
^C
--- stackoverflow.com ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 100.318/100.751/101.465 ms
/ # 

为什么会这样呢？

Answer 1

您还没有提到kubernetes的安装方式。您应该使用以下命令重新启动coredns pod。

kubectl -n kube-system rollout restart deployment coredns