问题：
Kubernetes不使用DNS-从pod到外部世界没有通信
姚俊材
我可能有kubernetes DNS问题，因为我的服务无法与外部世界通信（bitbucker.org）。实际上我找到了这个页面：https://kubernetes.io/docs/tasks/administer-cluster/dns-debugging-resolution/
并在我的集群上验证它（没有minikube）：
zordon@megazord:~$ kubectl exec busybox cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5
zordon@megazord:~$ kubectl exec -ti busybox -- nslookup kubernetes.default
Server: 10.96.0.10
Address 1: 10.96.0.10 kube-dns.kube-system.svc.cluster.local
nslookup: can't resolve 'kubernetes.default'
command terminated with exit code 1
args:
- --ip-masq
- --kube-subnet-mgr
args:
- --ip-masq
- --kube-subnet-mgr
- --iface=wlan0ec5
zordon@megazord:~$ kubectl get pods -n kube-system
NAME READY STATUS RESTARTS AGE
etcd-megazord 1/1 Running 1 21m
kube-apiserver-megazord 1/1 Running 1 21m
kube-controller-manager-megazord 1/1 Running 1 22m
kube-dns-86f4d74b45-8gh6q 3/3 Running 5 22m
kube-flannel-ds-2wqqr 1/1 Running 1 17m
kube-flannel-ds-59txb 1/1 Running 1 15m
kube-proxy-bdxb4 1/1 Running 1 15m
kube-proxy-mg44x 1/1 Running 1 22m
kube-scheduler-megazord 1/1 Running 1 22m
zordon@megazord:~$ kubectl get svc -n kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP 23m
zordon@megazord:~$ kubectl describe service kube-dns -n kube-system
Name: kube-dns
Namespace: kube-system
Labels: k8s-app=kube-dns
kubernetes.io/cluster-service=true
kubernetes.io/name=KubeDNS
Annotations: <none>
Selector: k8s-app=kube-dns
Type: ClusterIP
IP: 10.96.0.10
Port: dns 53/UDP
TargetPort: 53/UDP
Endpoints: 10.244.0.27:53
Port: dns-tcp 53/TCP
TargetPort: 53/TCP
Endpoints: 10.244.0.27:53
Session Affinity: None
Events: <none>
zordon@megazord:~$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c kubedns
I0419 17:40:11.473047 1 dns.go:48] version: 1.14.8
I0419 17:40:11.473975 1 server.go:71] Using configuration read from directory: /kube-dns-config with period 10s
I0419 17:40:11.474024 1 server.go:119] FLAG: --alsologtostderr="false"
I0419 17:40:11.474032 1 server.go:119] FLAG: --config-dir="/kube-dns-config"
I0419 17:40:11.474037 1 server.go:119] FLAG: --config-map=""
I0419 17:40:11.474041 1 server.go:119] FLAG: --config-map-namespace="kube-system"
I0419 17:40:11.474044 1 server.go:119] FLAG: --config-period="10s"
I0419 17:40:11.474049 1 server.go:119] FLAG: --dns-bind-address="0.0.0.0"
I0419 17:40:11.474053 1 server.go:119] FLAG: --dns-port="10053"
I0419 17:40:11.474058 1 server.go:119] FLAG: --domain="cluster.local."
I0419 17:40:11.474063 1 server.go:119] FLAG: --federations=""
I0419 17:40:11.474067 1 server.go:119] FLAG: --healthz-port="8081"
I0419 17:40:11.474071 1 server.go:119] FLAG: --initial-sync-timeout="1m0s"
I0419 17:40:11.474074 1 server.go:119] FLAG: --kube-master-url=""
I0419 17:40:11.474079 1 server.go:119] FLAG: --kubecfg-file=""
I0419 17:40:11.474082 1 server.go:119] FLAG: --log-backtrace-at=":0"
I0419 17:40:11.474087 1 server.go:119] FLAG: --log-dir=""
I0419 17:40:11.474091 1 server.go:119] FLAG: --log-flush-frequency="5s"
I0419 17:40:11.474094 1 server.go:119] FLAG: --logtostderr="true"
I0419 17:40:11.474098 1 server.go:119] FLAG: --nameservers=""
I0419 17:40:11.474101 1 server.go:119] FLAG: --stderrthreshold="2"
I0419 17:40:11.474104 1 server.go:119] FLAG: --v="2"
I0419 17:40:11.474107 1 server.go:119] FLAG: --version="false"
I0419 17:40:11.474113 1 server.go:119] FLAG: --vmodule=""
I0419 17:40:11.474190 1 server.go:201] Starting SkyDNS server (0.0.0.0:10053)
I0419 17:40:11.488125 1 server.go:220] Skydns metrics enabled (/metrics:10055)
I0419 17:40:11.488170 1 dns.go:146] Starting endpointsController
I0419 17:40:11.488180 1 dns.go:149] Starting serviceController
I0419 17:40:11.488348 1 logs.go:41] skydns: ready for queries on cluster.local. for tcp://0.0.0.0:10053 [rcache 0]
I0419 17:40:11.488407 1 logs.go:41] skydns: ready for queries on cluster.local. for udp://0.0.0.0:10053 [rcache 0]
I0419 17:40:11.988549 1 dns.go:170] Initialized services and endpoints from apiserver
I0419 17:40:11.988609 1 server.go:135] Setting up Healthz Handler (/readiness)
I0419 17:40:11.988641 1 server.go:140] Setting up cache handler (/cache)
I0419 17:40:11.988649 1 server.go:126] Status HTTP port 8081
zordon@megazord:~$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c dnsmasq
I0419 17:44:35.785171 1 main.go:76] opts: {{/usr/sbin/dnsmasq [-k --cache-size=1000 --no-negcache --log-facility=- --server=/cluster.local/127.0.0.1#10053 --server=/in-addr.arpa/127.0.0.1#10053 --server=/ip6.arpa/127.0.0.1#10053] true} /etc/k8s/dns/dnsmasq-nanny 10000000000}
I0419 17:44:35.785336 1 nanny.go:94] Starting dnsmasq [-k --cache-size=1000 --no-negcache --log-facility=- --server=/cluster.local/127.0.0.1#10053 --server=/in-addr.arpa/127.0.0.1#10053 --server=/ip6.arpa/127.0.0.1#10053]
I0419 17:44:35.876534 1 nanny.go:119]
W0419 17:44:35.876572 1 nanny.go:120] Got EOF from stdout
I0419 17:44:35.876578 1 nanny.go:116] dnsmasq[26]: started, version 2.78 cachesize 1000
I0419 17:44:35.876615 1 nanny.go:116] dnsmasq[26]: compile time options: IPv6 GNU-getopt no-DBus no-i18n no-IDN DHCP DHCPv6 no-Lua TFTP no-conntrack ipset auth no-DNSSEC loop-detect inotify
I0419 17:44:35.876632 1 nanny.go:116] dnsmasq[26]: using nameserver 127.0.0.1#10053 for domain ip6.arpa
I0419 17:44:35.876642 1 nanny.go:116] dnsmasq[26]: using nameserver 127.0.0.1#10053 for domain in-addr.arpa
I0419 17:44:35.876653 1 nanny.go:116] dnsmasq[26]: using nameserver 127.0.0.1#10053 for domain cluster.local
I0419 17:44:35.876666 1 nanny.go:116] dnsmasq[26]: reading /etc/resolv.conf
I0419 17:44:35.876677 1 nanny.go:116] dnsmasq[26]: using nameserver 127.0.0.1#10053 for domain ip6.arpa
I0419 17:44:35.876691 1 nanny.go:116] dnsmasq[26]: using nameserver 127.0.0.1#10053 for domain in-addr.arpa
I0419 17:44:35.876701 1 nanny.go:116] dnsmasq[26]: using nameserver 127.0.0.1#10053 for domain cluster.local
I0419 17:44:35.876709 1 nanny.go:116] dnsmasq[26]: using nameserver 127.0.0.53#53
I0419 17:44:35.876717 1 nanny.go:116] dnsmasq[26]: read /etc/hosts - 7 addresses
**zordon@megazord:~$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c sidecar**
I0419 17:45:06.726670 1 main.go:51] Version v1.14.8
I0419 17:45:06.726781 1 server.go:45] Starting server (options {DnsMasqPort:53 DnsMasqAddr:127.0.0.1 DnsMasqPollIntervalMs:5000 Probes:[{Label:kubedns Server:127.0.0.1:10053 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:33} {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:33}] PrometheusAddr:0.0.0.0 PrometheusPort:10054 PrometheusPath:/metrics PrometheusNamespace:kubedns})
I0419 17:45:06.726842 1 dnsprobe.go:75] Starting dnsProbe {Label:kubedns Server:127.0.0.1:10053 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:33}
I0419 17:45:06.726927 1 dnsprobe.go:75] Starting dnsProbe {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:33}
主节点：
zordon@megazord:~$ ip -d route
unicast default via 192.168.1.1 dev wlp32s0 proto static scope global metric 600
unicast 10.244.0.0/24 dev cni0 proto kernel scope link src 10.244.0.1
unicast 10.244.1.0/24 via 10.244.1.0 dev flannel.1 proto boot scope global onlink
unicast 169.254.0.0/16 dev wlp32s0 proto boot scope link metric 1000
unicast 172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1
unicast 192.168.1.0/24 dev wlp32s0 proto kernel scope link src 192.168.1.110 metric 600
zordon@megazord:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp30s0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether 4c:cc:6a:f8:7e:4b brd ff:ff:ff:ff:ff:ff
3: wlp32s0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether ec:08:6b:0c:9c:27 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.110/24 brd 192.168.1.255 scope global wlp32s0
valid_lft forever preferred_lft forever
inet6 fe80::f632:2f08:9caa:2c82/64 scope link
valid_lft forever preferred_lft forever
4: docker0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default
link/ether 02:42:32:19:f7:5a brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::42:32ff:fe19:f75a/64 scope link
valid_lft forever preferred_lft forever
6: vethf9de74d@if5: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master docker0 state UP group default
link/ether ba:af:58:a0:4a:74 brd ff:ff:ff:ff:ff:ff link-netnsid 0
inet6 fe80::b8af:58ff:fea0:4a74/64 scope link
valid_lft forever preferred_lft forever
7: flannel.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UNKNOWN group default
link/ether a6:d1:45:73:c3:31 brd ff:ff:ff:ff:ff:ff
inet 10.244.0.0/32 scope global flannel.1
valid_lft forever preferred_lft forever
inet6 fe80::a4d1:45ff:fe73:c331/64 scope link
valid_lft forever preferred_lft forever
8: cni0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UP group default qlen 1000
link/ether 0a:58:0a:f4:00:01 brd ff:ff:ff:ff:ff:ff
inet 10.244.0.1/24 scope global cni0
valid_lft forever preferred_lft forever
inet6 fe80::24f5:4cff:fee9:a32d/64 scope link
valid_lft forever preferred_lft forever
9: veth58367f89@if3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue master cni0 state UP group default
link/ether 7a:29:e9:c8:bf:3f brd ff:ff:ff:ff:ff:ff link-netnsid 1
inet6 fe80::7829:e9ff:fec8:bf3f/64 scope link
valid_lft forever preferred_lft forever
节点工作者：
zordon@k8s-minion-one:~$ ip -d route
unicast default via 192.168.1.1 dev enp0s25 proto dhcp scope global src 192.168.1.111 metric 100
unicast 10.244.0.0/24 via 10.244.0.0 dev flannel.1 proto boot scope global onlink
unicast 10.244.1.0/24 dev cni0 proto kernel scope link src 10.244.1.1 linkdown
unicast 172.17.0.0/16 dev docker0 proto kernel scope link src 172.17.0.1 linkdown
unicast 192.168.1.0/24 dev enp0s25 proto kernel scope link src 192.168.1.111
unicast 192.168.1.1 dev enp0s25 proto dhcp scope link src 192.168.1.111 metric 100
zordon@k8s-minion-one:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: enp0s25: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 18:03:73:45:75:71 brd ff:ff:ff:ff:ff:ff
inet 192.168.1.111/24 brd 192.168.1.255 scope global enp0s25
valid_lft forever preferred_lft forever
inet6 fe80::1a03:73ff:fe45:7571/64 scope link
valid_lft forever preferred_lft forever
3: docker0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default
link/ether 02:42:38:3e:a3:94 brd ff:ff:ff:ff:ff:ff
inet 172.17.0.1/16 brd 172.17.255.255 scope global docker0
valid_lft forever preferred_lft forever
inet6 fe80::42:38ff:fe3e:a394/64 scope link
valid_lft forever preferred_lft forever
4: flannel.1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc noqueue state UNKNOWN group default
link/ether 7a:d0:2a:b4:73:43 brd ff:ff:ff:ff:ff:ff
inet 10.244.1.0/32 scope global flannel.1
valid_lft forever preferred_lft forever
inet6 fe80::78d0:2aff:feb4:7343/64 scope link
valid_lft forever preferred_lft forever
5: cni0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
link/ether 0a:58:0a:f4:01:01 brd ff:ff:ff:ff:ff:ff
inet 10.244.1.1/24 scope global cni0
valid_lft forever preferred_lft forever
inet6 fe80::7440:12ff:fefa:f55/64 scope link
valid_lft forever preferred_lft forever
共有1个答案
华易安
我发现了问题所在。当我部署busybox并尝试用name ping外部服务器时会出现问题。当我使用IP地址时问题不存在。因此DNS和名称解析中存在的问题。在ping过程中，我查看dns日志并查看问题。帮助我配置了DN的映射：
apiVersion: v1
kind: ConfigMap
metadata:
name: kube-dns
namespace: kube-system
labels:
addonmanager.kubernetes.io/mode: EnsureExists
data:
upstreamNameservers: |-
["8.8.8.8", "8.8.4.4"]
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