[root@k8s k8s]# kubectl get pods --all-namespaces -o wide
NAMESPACE     NAME                                         READY   STATUS              RESTARTS         AGE     IP              NODE                 NOMINATED NODE   READINESS GATES
default       dnsutils                                     0/1     ContainerCreating   0                2m6s    <none>          k8s.node.worker.01   <none>           <none>
default       nginx-controller-gfdcs                       1/1     Running             0                20m     10.244.2.8      k8s.node.worker.02   <none>           <none>
default       nginx-controller-tph7m                       1/1     Running             0                20m     10.244.2.9      k8s.node.worker.02   <none>           <none>
kube-system   coredns-54d6774dfc-p7ln4                     0/1     CrashLoopBackOff    7 (2m44s ago)    46h     10.244.0.7      k8s.node.master.01   <none>           <none>
kube-system   coredns-54d6774dfc-zckts                     0/1     CrashLoopBackOff    7 (2m40s ago)    46h     10.244.0.6      k8s.node.master.01   <none>           <none>
kube-system   etcd-k8s.node.master.01                      1/1     Running             1 (5m55s ago)    46h     172.16.34.125   k8s.node.master.01   <none>           <none>
kube-system   kube-apiserver-k8s.node.master.01            1/1     Running             1 (5m45s ago)    132m    172.16.34.125   k8s.node.master.01   <none>           <none>
kube-system   kube-controller-manager-k8s.node.master.01   1/1     Running      

[root@k8s k8s]# kubectl logs coredns-54d6774dfc-p7ln4 -n kube-system
plugin/forward: no nameservers found

解决：
node节点
/etc/resolv.conf
nameserver 不得为空

##################

NetworkPlugin cni failed to set up pod "coredns-5c98db65d4-fr9nk_kube-system" network: failed to set bridge addr: "cni0" already has an IP address different from 172.21.0.1/24NetworkPlugin cni failed to set up pod "coredns-5c98db65d4-fr9nk_kube-system" network: failed to set bridge addr: "cni0" already has an IP address different from 172.21.0.1/24
###
[root@k8s flannel]# ifconfig  cni0 down
[root@k8s flannel]# brctl delbr cni0
bridge cni0 is still up; can't delete it
[root@k8s flannel]# brctl delbr cni0
bridge cni0 is still up; can't delete it
[root@k8s flannel]# brctl delbr cni0
bridge cni0 is still up; can't delete it
[root@k8s flannel]# ifconfig
cni0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1450
        inet 10.244.0.1  netmask 255.255.255.0  broadcast 10.244.0.255
        inet6 fe80::bc58:16ff:fe36:5bf7  prefixlen 64  scopeid 0x20<link>
        ether be:58:16:36:5b:f7  txqueuelen 1000  (Ethernet)
        RX packets 2496  bytes 126017 (123.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1662  bytes 121056 (118.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

解决：kubeadm reset | kubectl apply -f kube-flannel.yml

参考：https://blog.csdn.net/yujia_666/article/details/107719919