Dns 库伯内特斯：豆荚可以'；无法解析主机名

我遇到了Kubernetes的问题，我的POD无法解析主机名（例如

google.com

或

Kubernetes.default

）

我目前在OpenStack的两个CentOS7实例上运行1个主节点和1个节点。我使用

kubeadm

进行部署

以下是已安装的版本：

kubeadm-1.7.3-1.x86_64
kubectl-1.7.3-1.x86_64
kubelet-1.7.3-1.x86_64
kubernetes-cni-0.5.1-0.x86_64

下面概述了一些验证步骤，也许可以让您对我的问题有一些了解

我定义了一个busybox pod：

apiVersion: v1
kind: Pod
metadata:
  name: busybox
  namespace: default
spec:
  containers:
  - image: busybox
    command:
      - sleep
      - "3600"
    imagePullPolicy: IfNotPresent
    name: busybox
  restartPolicy: Always

然后创建pod：

$ kubectl create -f busybox.yaml

尝试对名称

google.com

执行DNS查找：

$ kubectl exec -ti busybox -- nslookup google.com
Server:    10.96.0.10
Address 1: 10.96.0.10
nslookup: can't resolve 'google.com'

尝试对名称

kubernetes执行DNS查找。默认值
：

$ kubectl exec -ti busybox -- nslookup kubernetes.default
Server:    10.96.0.10
Address 1: 10.96.0.10
nslookup: can't resolve 'kubernetes.default'

检查我的DNS吊舱是否正在运行：

$ kubectl get pods --namespace=kube-system -l k8s-app=kube-dns
NAME                        READY     STATUS    RESTARTS   AGE
kube-dns-2425271678-k1nft   3/3       Running   9          5d

检查我的DNS服务是否已启动：

$ kubectl get svc --namespace=kube-system
NAME       CLUSTER-IP   EXTERNAL-IP   PORT(S)         AGE
kube-dns   10.96.0.10   <none>        53/UDP,53/TCP   5d

检查我的容器中
/etc/resolv.conf
的内容：

$ kubectl exec -ti busybox -- cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5

$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c kubedns
I0817 20:54:58.445280       1 dns.go:48] version: 1.14.3-4-gee838f6
I0817 20:54:58.452551       1 server.go:70] Using configuration read from directory: /kube-dns-config with period 10s
I0817 20:54:58.452616       1 server.go:113] FLAG: --alsologtostderr="false"
I0817 20:54:58.452628       1 server.go:113] FLAG: --config-dir="/kube-dns-config"
I0817 20:54:58.452638       1 server.go:113] FLAG: --config-map=""
I0817 20:54:58.452643       1 server.go:113] FLAG: --config-map-namespace="kube-system"
I0817 20:54:58.452650       1 server.go:113] FLAG: --config-period="10s"
I0817 20:54:58.452659       1 server.go:113] FLAG: --dns-bind-address="0.0.0.0"
I0817 20:54:58.452665       1 server.go:113] FLAG: --dns-port="10053"
I0817 20:54:58.452674       1 server.go:113] FLAG: --domain="cluster.local."
I0817 20:54:58.452683       1 server.go:113] FLAG: --federations=""
I0817 20:54:58.452692       1 server.go:113] FLAG: --healthz-port="8081"
I0817 20:54:58.452698       1 server.go:113] FLAG: --initial-sync-timeout="1m0s"
I0817 20:54:58.452704       1 server.go:113] FLAG: --kube-master-url=""
I0817 20:54:58.452713       1 server.go:113] FLAG: --kubecfg-file=""
I0817 20:54:58.452718       1 server.go:113] FLAG: --log-backtrace-at=":0"
I0817 20:54:58.452727       1 server.go:113] FLAG: --log-dir=""
I0817 20:54:58.452734       1 server.go:113] FLAG: --log-flush-frequency="5s"
I0817 20:54:58.452741       1 server.go:113] FLAG: --logtostderr="true"
I0817 20:54:58.452746       1 server.go:113] FLAG: --nameservers=""
I0817 20:54:58.452752       1 server.go:113] FLAG: --stderrthreshold="2"
I0817 20:54:58.452759       1 server.go:113] FLAG: --v="2"
I0817 20:54:58.452765       1 server.go:113] FLAG: --version="false"
I0817 20:54:58.452775       1 server.go:113] FLAG: --vmodule=""
I0817 20:54:58.452856       1 server.go:176] Starting SkyDNS server (0.0.0.0:10053)
I0817 20:54:58.453680       1 server.go:198] Skydns metrics enabled (/metrics:10055)
I0817 20:54:58.453692       1 dns.go:147] Starting endpointsController
I0817 20:54:58.453699       1 dns.go:150] Starting serviceController
I0817 20:54:58.453841       1 logs.go:41] skydns: ready for queries on cluster.local. for tcp://0.0.0.0:10053 [rcache 0]
I0817 20:54:58.453852       1 logs.go:41] skydns: ready for queries on cluster.local. for udp://0.0.0.0:10053 [rcache 0]
I0817 20:54:58.964468       1 dns.go:171] Initialized services and endpoints from apiserver
I0817 20:54:58.964523       1 server.go:129] Setting up Healthz Handler (/readiness)
I0817 20:54:58.964536       1 server.go:134] Setting up cache handler (/cache)
I0817 20:54:58.964545       1 server.go:120] Status HTTP port 8081

$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c sidecar
ERROR: logging before flag.Parse: I0817 20:55:04.488391       1 main.go:48] Version v1.14.3-4-gee838f6
ERROR: logging before flag.Parse: I0817 20:55:04.488612       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:1} {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}] PrometheusAddr:0.0.0.0 PrometheusPort:10054 PrometheusPath:/metrics PrometheusNamespace:kubedns})
ERROR: logging before flag.Parse: I0817 20:55:04.488667       1 dnsprobe.go:75] Starting dnsProbe {Label:kubedns Server:127.0.0.1:10053 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}
ERROR: logging before flag.Parse: I0817 20:55:04.488766       1 dnsprobe.go:75] Starting dnsProbe {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}

如果我理解正确，Kubernetes文档说明我的POD应该继承节点（或主节点？）的DNS配置。但是，即使只有一行（
nameserver 10.92.128.40
），我在旋转吊舱时也会收到以下警告：

Search Line limits were exceeded, some dns names have been omitted, the applied search line is: default.svc.cluster.local svc.cluster.local cluster.local mydomain.net anotherdomain.net yetanotherdomain.net

我知道存在一个已知问题，即在
/etc/resolv.conf
中只能列出这么多项目。但是，我的容器中的上述搜索行和名称服务器将从何处生成

最后，这里是来自
kube dns
容器的日志：

$ kubectl exec -ti busybox -- cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5

$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c kubedns
I0817 20:54:58.445280       1 dns.go:48] version: 1.14.3-4-gee838f6
I0817 20:54:58.452551       1 server.go:70] Using configuration read from directory: /kube-dns-config with period 10s
I0817 20:54:58.452616       1 server.go:113] FLAG: --alsologtostderr="false"
I0817 20:54:58.452628       1 server.go:113] FLAG: --config-dir="/kube-dns-config"
I0817 20:54:58.452638       1 server.go:113] FLAG: --config-map=""
I0817 20:54:58.452643       1 server.go:113] FLAG: --config-map-namespace="kube-system"
I0817 20:54:58.452650       1 server.go:113] FLAG: --config-period="10s"
I0817 20:54:58.452659       1 server.go:113] FLAG: --dns-bind-address="0.0.0.0"
I0817 20:54:58.452665       1 server.go:113] FLAG: --dns-port="10053"
I0817 20:54:58.452674       1 server.go:113] FLAG: --domain="cluster.local."
I0817 20:54:58.452683       1 server.go:113] FLAG: --federations=""
I0817 20:54:58.452692       1 server.go:113] FLAG: --healthz-port="8081"
I0817 20:54:58.452698       1 server.go:113] FLAG: --initial-sync-timeout="1m0s"
I0817 20:54:58.452704       1 server.go:113] FLAG: --kube-master-url=""
I0817 20:54:58.452713       1 server.go:113] FLAG: --kubecfg-file=""
I0817 20:54:58.452718       1 server.go:113] FLAG: --log-backtrace-at=":0"
I0817 20:54:58.452727       1 server.go:113] FLAG: --log-dir=""
I0817 20:54:58.452734       1 server.go:113] FLAG: --log-flush-frequency="5s"
I0817 20:54:58.452741       1 server.go:113] FLAG: --logtostderr="true"
I0817 20:54:58.452746       1 server.go:113] FLAG: --nameservers=""
I0817 20:54:58.452752       1 server.go:113] FLAG: --stderrthreshold="2"
I0817 20:54:58.452759       1 server.go:113] FLAG: --v="2"
I0817 20:54:58.452765       1 server.go:113] FLAG: --version="false"
I0817 20:54:58.452775       1 server.go:113] FLAG: --vmodule=""
I0817 20:54:58.452856       1 server.go:176] Starting SkyDNS server (0.0.0.0:10053)
I0817 20:54:58.453680       1 server.go:198] Skydns metrics enabled (/metrics:10055)
I0817 20:54:58.453692       1 dns.go:147] Starting endpointsController
I0817 20:54:58.453699       1 dns.go:150] Starting serviceController
I0817 20:54:58.453841       1 logs.go:41] skydns: ready for queries on cluster.local. for tcp://0.0.0.0:10053 [rcache 0]
I0817 20:54:58.453852       1 logs.go:41] skydns: ready for queries on cluster.local. for udp://0.0.0.0:10053 [rcache 0]
I0817 20:54:58.964468       1 dns.go:171] Initialized services and endpoints from apiserver
I0817 20:54:58.964523       1 server.go:129] Setting up Healthz Handler (/readiness)
I0817 20:54:58.964536       1 server.go:134] Setting up cache handler (/cache)
I0817 20:54:58.964545       1 server.go:120] Status HTTP port 8081

$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c sidecar
ERROR: logging before flag.Parse: I0817 20:55:04.488391       1 main.go:48] Version v1.14.3-4-gee838f6
ERROR: logging before flag.Parse: I0817 20:55:04.488612       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:1} {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}] PrometheusAddr:0.0.0.0 PrometheusPort:10054 PrometheusPath:/metrics PrometheusNamespace:kubedns})
ERROR: logging before flag.Parse: I0817 20:55:04.488667       1 dnsprobe.go:75] Starting dnsProbe {Label:kubedns Server:127.0.0.1:10053 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}
ERROR: logging before flag.Parse: I0817 20:55:04.488766       1 dnsprobe.go:75] Starting dnsProbe {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}

dnsmasq
容器。不管它发现了多个名称服务器，而不仅仅是我在
resolv.conf
中提到的名称服务器，因为我在它们原来的名称服务器中找到了更多的名称服务器。我试图简单地通过删除附加项来实现：

$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c dnsmasq
I0817 20:55:03.295826       1 main.go:76] opts: {{/usr/sbin/dnsmasq [-k --cache-size=1000 --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}
I0817 20:55:03.298134       1 nanny.go:86] Starting dnsmasq [-k --cache-size=1000 --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]
I0817 20:55:03.731577       1 nanny.go:111] 
W0817 20:55:03.731609       1 nanny.go:112] Got EOF from stdout
I0817 20:55:03.731642       1 nanny.go:108] dnsmasq[9]: started, version 2.76 cachesize 1000
I0817 20:55:03.731656       1 nanny.go:108] dnsmasq[9]: 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
I0817 20:55:03.731681       1 nanny.go:108] dnsmasq[9]: using nameserver 127.0.0.1#10053 for domain ip6.arpa 
I0817 20:55:03.731689       1 nanny.go:108] dnsmasq[9]: using nameserver 127.0.0.1#10053 for domain in-addr.arpa 
I0817 20:55:03.731695       1 nanny.go:108] dnsmasq[9]: using nameserver 127.0.0.1#10053 for domain cluster.local 
I0817 20:55:03.731704       1 nanny.go:108] dnsmasq[9]: reading /etc/resolv.conf
I0817 20:55:03.731710       1 nanny.go:108] dnsmasq[9]: using nameserver 127.0.0.1#10053 for domain ip6.arpa 
I0817 20:55:03.731717       1 nanny.go:108] dnsmasq[9]: using nameserver 127.0.0.1#10053 for domain in-addr.arpa 
I0817 20:55:03.731723       1 nanny.go:108] dnsmasq[9]: using nameserver 127.0.0.1#10053 for domain cluster.local 
I0817 20:55:03.731729       1 nanny.go:108] dnsmasq[9]: using nameserver 10.92.128.40#53
I0817 20:55:03.731735       1 nanny.go:108] dnsmasq[9]: using nameserver 10.92.128.41#53
I0817 20:55:03.731741       1 nanny.go:108] dnsmasq[9]: using nameserver 10.95.207.66#53
I0817 20:55:03.731747       1 nanny.go:108] dnsmasq[9]: read /etc/hosts - 7 addresses

和
侧车
集装箱：

$ kubectl exec -ti busybox -- cat /etc/resolv.conf
nameserver 10.96.0.10
search default.svc.cluster.local svc.cluster.local cluster.local
options ndots:5

$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c kubedns
I0817 20:54:58.445280       1 dns.go:48] version: 1.14.3-4-gee838f6
I0817 20:54:58.452551       1 server.go:70] Using configuration read from directory: /kube-dns-config with period 10s
I0817 20:54:58.452616       1 server.go:113] FLAG: --alsologtostderr="false"
I0817 20:54:58.452628       1 server.go:113] FLAG: --config-dir="/kube-dns-config"
I0817 20:54:58.452638       1 server.go:113] FLAG: --config-map=""
I0817 20:54:58.452643       1 server.go:113] FLAG: --config-map-namespace="kube-system"
I0817 20:54:58.452650       1 server.go:113] FLAG: --config-period="10s"
I0817 20:54:58.452659       1 server.go:113] FLAG: --dns-bind-address="0.0.0.0"
I0817 20:54:58.452665       1 server.go:113] FLAG: --dns-port="10053"
I0817 20:54:58.452674       1 server.go:113] FLAG: --domain="cluster.local."
I0817 20:54:58.452683       1 server.go:113] FLAG: --federations=""
I0817 20:54:58.452692       1 server.go:113] FLAG: --healthz-port="8081"
I0817 20:54:58.452698       1 server.go:113] FLAG: --initial-sync-timeout="1m0s"
I0817 20:54:58.452704       1 server.go:113] FLAG: --kube-master-url=""
I0817 20:54:58.452713       1 server.go:113] FLAG: --kubecfg-file=""
I0817 20:54:58.452718       1 server.go:113] FLAG: --log-backtrace-at=":0"
I0817 20:54:58.452727       1 server.go:113] FLAG: --log-dir=""
I0817 20:54:58.452734       1 server.go:113] FLAG: --log-flush-frequency="5s"
I0817 20:54:58.452741       1 server.go:113] FLAG: --logtostderr="true"
I0817 20:54:58.452746       1 server.go:113] FLAG: --nameservers=""
I0817 20:54:58.452752       1 server.go:113] FLAG: --stderrthreshold="2"
I0817 20:54:58.452759       1 server.go:113] FLAG: --v="2"
I0817 20:54:58.452765       1 server.go:113] FLAG: --version="false"
I0817 20:54:58.452775       1 server.go:113] FLAG: --vmodule=""
I0817 20:54:58.452856       1 server.go:176] Starting SkyDNS server (0.0.0.0:10053)
I0817 20:54:58.453680       1 server.go:198] Skydns metrics enabled (/metrics:10055)
I0817 20:54:58.453692       1 dns.go:147] Starting endpointsController
I0817 20:54:58.453699       1 dns.go:150] Starting serviceController
I0817 20:54:58.453841       1 logs.go:41] skydns: ready for queries on cluster.local. for tcp://0.0.0.0:10053 [rcache 0]
I0817 20:54:58.453852       1 logs.go:41] skydns: ready for queries on cluster.local. for udp://0.0.0.0:10053 [rcache 0]
I0817 20:54:58.964468       1 dns.go:171] Initialized services and endpoints from apiserver
I0817 20:54:58.964523       1 server.go:129] Setting up Healthz Handler (/readiness)
I0817 20:54:58.964536       1 server.go:134] Setting up cache handler (/cache)
I0817 20:54:58.964545       1 server.go:120] Status HTTP port 8081

$ kubectl logs --namespace=kube-system $(kubectl get pods --namespace=kube-system -l k8s-app=kube-dns -o name) -c sidecar
ERROR: logging before flag.Parse: I0817 20:55:04.488391       1 main.go:48] Version v1.14.3-4-gee838f6
ERROR: logging before flag.Parse: I0817 20:55:04.488612       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:1} {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}] PrometheusAddr:0.0.0.0 PrometheusPort:10054 PrometheusPath:/metrics PrometheusNamespace:kubedns})
ERROR: logging before flag.Parse: I0817 20:55:04.488667       1 dnsprobe.go:75] Starting dnsProbe {Label:kubedns Server:127.0.0.1:10053 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}
ERROR: logging before flag.Parse: I0817 20:55:04.488766       1 dnsprobe.go:75] Starting dnsProbe {Label:dnsmasq Server:127.0.0.1:53 Name:kubernetes.default.svc.cluster.local. Interval:5s Type:1}

我一直在阅读提供的文档。任何方向、见解或尝试的东西都将不胜感激
 我想到了一些想法：


可能kube代理服务工作不正常，因此无法访问kube dns服务。你能检查一下它是否工作吗
您没有正确安装网络覆盖，例如Calico:。您安装了它并且它正在工作吗
遇到了同样的问题。我遵循这个文档，检查了与DNS相关的POD、服务、端点，所有这些都在运行，没有错误消息。最后，我发现我的印花布服务已经失效。在我启动calico服务并等待了几分钟后，它开始工作。
如果您看到以下错误，请检查coredns pods日志：

# kubectl logs --namespace=kube-system coredns-XXX
  ...
  [ERROR] plugin/errors ... HINFO: read udp ... read: no route to host

然后确保主机上已启用firewalld伪装：

# firewall-cmd --list-all
  ... 
  masquerade: yes

Enable if it's "no":
# firewall-cmd --add-masquerade --permanent
# firewall-cmd --reload

*在此之后，您可能需要重新启动/重新启动。我遇到了类似的问题。重新启动coredns部署为我解决了这一问题：

kubectl -n kube-system rollout restart deployment coredns

您好，kube代理正在运行：
/usr/local/bin/kube proxy--kubeconfig=/var/lib/kube proxy/kubeconfig.conf--cluster cidr=10.244.0.0/16
。根据，代理正在节点上创建所需的iptables规则。奇怪的是，对服务运行
curl10.111.133.184:80
有时会返回一个pod名称，其他时候我会得到“没有到主机的路由”。在进行
kubeadm
设置时，我确实选择了法兰绒。你能指出如何测试它的方向吗？好的，如果我理解正确的话，Flannel提供了一个覆盖网络，这样吊舱可以跨不同的节点相互通信。My
kube-dns-2425271678-k1nft
pod的IP为
10.244.0.5
。这是一个由Flannel处理的IP（在
/run/Flannel/subnet.env
中定义）。此DNS吊舱位于节点
kubemaster
上。现在，我创建的pod位于节点
kubenode01
上。我可以从
kubemaster
中ping
10.244.0.5
，但不能从
kubenode01
中ping。我认为这可能是法兰绒的问题，对吗？我的耳朵后面湿透了，所以为愚蠢的问题道歉。再补充一点关于测试代理。。我可以创建两个运行nginx的pod，将它们添加到一个服务中，该服务的
端口为
80'，节点端口为
31746
。然后，我可以使用该节点的外部IP地址和上述端口从外部访问该服务。这是否证明kube代理至少可以正常工作，因为它似乎成功地将流量转发到pods？我几乎100%确定这个问题与覆盖有关。运行
kubectl exec--namespace kube系统-it kube-dns-2425271678-k1nft--container kubedns--ping google.com
效果很好，因为kube dns在主机上运行。它也适用于在主机上运行的任何其他pod，如kube flannel、kube proxy等。。但是，在worker上创建的任何pod都无法解析DNS，这可能是因为它们无法访问DNS服务，因为Flannel出现了一些问题。我将开始研究如何缩小范围，但任何建议都将不胜感激！因此，我在我的主节点和节点上重新启动了docker和kubelet服务，您知道什么。。一切都开始起作用了。。我不知道我做了什么，也不知道为什么它不起作用，但全面刷新这两项服务不知怎么解决了问题。我希望我一开始就这么做了！谢谢你帮了我一把。我肯定要进一步了解Kubernetes的工作原理：）k8s运行的节点的名称解析了吗？应该重新启动什么？@cryptoparty restart network like
systemctl restart network
coredns正在运行，我认为它一定很好，但重新启动它很有魅力，谢谢。我的coredns运行良好，没有错误，但是这个命令很好地解决了我的问题。我非常感谢，我决定登录并按下向上投票。这解决了我的问题。谢谢你的命令！这可以解决我的问题。不知道为什么。