我已经构建了一个新的Kubernetes集群v1.20.1，它有单个主节点和单个工作节点，并使用Calico CNI。
我在默认命名空间中部署了busybox pod。
# kubectl get pods busybox -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
busybox 1/1 Running 0 12m 10.203.0.129 node02 <none> <none>
nslookup无法工作
kubectl exec -ti busybox -- nslookup kubernetes.default
Server: 10.96.0.10
Address 1: 10.96.0.10
nslookup: can't resolve 'kubernetes.default'
集群正在运行最新更新的RHEL 8操作系统。
按照以下步骤：https://kubernetes.io/docs/tasks/administer-cluster/dns-debugging-resolution/
nslookup命令无法连接到域名解析服务器。
# kubectl exec -i -t dnsutils -- nslookup kubernetes.default
;; connection timed out; no servers could be reached
command terminated with exit code 1
resolve.conf 文件
# kubectl exec -ti dnsutils -- cat /etc/resolv.conf
search default.svc.cluster.local svc.cluster.local cluster.local
nameserver 10.96.0.10
options ndots:5
DNS pod正在运行。
# kubectl get pods --namespace=kube-system -l k8s-app=kube-dns
NAME READY STATUS RESTARTS AGE
coredns-74ff55c5b-472vx 1/1 Running 1 85m
coredns-74ff55c5b-c75bq 1/1 Running 1 85m
DNS Pod 日志
kubectl logs --namespace=kube-system -l k8s-app=kube-dns
.:53
[INFO] plugin/reload: Running configuration MD5 = db32ca3650231d74073ff4cf814959a7
CoreDNS-1.7.0
linux/amd64, go1.14.4, f59c03d
.:53
[INFO] plugin/reload: Running configuration MD5 = db32ca3650231d74073ff4cf814959a7
CoreDNS-1.7.0
linux/amd64, go1.14.4, f59c03d
Service的定义
# kubectl get svc --namespace=kube-system
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
kube-dns ClusterIP 10.96.0.10 <none> 53/UDP,53/TCP,9153/TCP 86m
**I can see the endpoints of DNS pod**
# kubectl get endpoints kube-dns --namespace=kube-system
NAME ENDPOINTS AGE
kube-dns 10.203.0.5:53,10.203.0.6:53,10.203.0.5:53 + 3 more... 86m
已启用日志记录，但未看到流量传输到 DNS pod
# kubectl logs --namespace=kube-system -l k8s-app=kube-dns
.:53
[INFO] plugin/reload: Running configuration MD5 = db32ca3650231d74073ff4cf814959a7
CoreDNS-1.7.0
linux/amd64, go1.14.4, f59c03d
.:53
[INFO] plugin/reload: Running configuration MD5 = db32ca3650231d74073ff4cf814959a7
CoreDNS-1.7.0
linux/amd64, go1.14.4, f59c03d
我可以ping通DNS POD
# kubectl exec -i -t dnsutils -- ping 10.203.0.5
PING 10.203.0.5 (10.203.0.5): 56 data bytes
64 bytes from 10.203.0.5: seq=0 ttl=62 time=6.024 ms
64 bytes from 10.203.0.5: seq=1 ttl=62 time=6.052 ms
64 bytes from 10.203.0.5: seq=2 ttl=62 time=6.175 ms
64 bytes from 10.203.0.5: seq=3 ttl=62 time=6.000 ms
^C
--- 10.203.0.5 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 6.000/6.062/6.175 ms
nmap显示端口过滤
# ke netshoot-6f677d4fdf-5t5cb -- nmap 10.203.0.5
Starting Nmap 7.80 ( https://nmap.org ) at 2021-01-15 22:29 UTC
Nmap scan report for 10.203.0.5
Host is up (0.0060s latency).
Not shown: 997 closed ports
PORT STATE SERVICE
53/tcp filtered domain
8080/tcp filtered http-proxy
8181/tcp filtered intermapper
Nmap done: 1 IP address (1 host up) scanned in 14.33 seconds
如果我在主节点上安排POD，nslookup工作并且nmap显示端口打开吗？
# ke netshoot -- bash
bash-5.0# nslookup kubernetes.default
Server: 10.96.0.10
Address: 10.96.0.10#53
Name: kubernetes.default.svc.cluster.local
Address: 10.96.0.1
nmap -p 53 10.96.0.10
Starting Nmap 7.80 ( https://nmap.org ) at 2021-01-15 22:46 UTC
Nmap scan report for kube-dns.kube-system.svc.cluster.local (10.96.0.10)
Host is up (0.000098s latency).
PORT STATE SERVICE
53/tcp open domain
Nmap done: 1 IP address (1 host up) scanned in 0.14 seconds
为什么在工作节点上运行的 POD 上执行 nslookup 无法正常工作？如何排除这个问题？
我已经重新构建了服务器两次，但问题依旧存在。
谢谢
SR
更新，添加 kubeadm 配置文件
# cat kubeadm-config.yaml
---
apiVersion: kubeadm.k8s.io/v1beta2
bootstrapTokens:
- groups:
- system:bootstrappers:kubeadm:default-node-token
token: abcdef.0123456789abcdef
ttl: 24h0m0s
usages:
- signing
- authentication
kind: InitConfiguration
nodeRegistration:
criSocket: unix:///run/containerd/containerd.sock
taints:
- effect: NoSchedule
key: node-role.kubernetes.io/master
kubeletExtraArgs:
cgroup-driver: "systemd"
---
apiVersion: kubeadm.k8s.io/v1beta2
kind: ClusterConfiguration
kubernetesVersion: stable
controlPlaneEndpoint: "master01:6443"
networking:
dnsDomain: cluster.local
podSubnet: 10.0.0.0/14
serviceSubnet: 10.96.0.0/12
---
apiVersion: kubeproxy.config.k8s.io/v1alpha1
kind: KubeProxyConfiguration
mode: "ipvs
"
busybox:1.28，但仍然出现相同的错误nslookup: can't resolve 'kubernetes.default'。如果我在主节点上运行 busybox，则 nslookup 可以正常工作，但从工作节点上无法正常工作。 - sfgroupsCalico Pods的状态和日志吗（特别是来自你的工作节点的那个）？ - matt_j53用于DNS访问？ 您是否禁用了SELinux？ 您是否使用默认设置+自定义pod-network cidr通过kubeadm引导了k8s？ 您能否分享您的确切pod-network-cidr和service-cidr？ 您是否有任何其他集群配置，例如k8s网络策略、calico网络策略？ 您是否符合这些要求？ 您是否遵循了关于在rhel 8上安装和配置k8s的官方文档？ - matt_j