我使用 kubeadm 在带有 flannel 的 Ubuntu 16.04 LTS 上设置了一个单节点 Kubernetes 集群。
大多数情况下一切正常，但每隔几天，集群就会进入无法调度新 Pod 的状态——Pod 卡在“Pending”状态，当我kubectl describe pod在这些 Pod 中时，我会收到类似这样的错误消息：
Events:
FirstSeen LastSeen Count From SubObjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
2m 2m 1 {default-scheduler } Normal Scheduled Successfully assigned dex-1939802596-zt1r3 to superserver-03
1m 2s 21 {kubelet superserver-03} Warning FailedSync Error syncing pod, skipping: failed to "SetupNetwork" for "somepod-1939802596-zt1r3_somenamespace" with SetupNetworkError: "Failed to setup network for pod \"somepod-1939802596-zt1r3_somenamespace(167f8345-faeb-11e6-94f3-0cc47a9a5cf2)\" using network plugins \"cni\": no IP addresses available in network: cbr0; Skipping pod"
我发现了这个stackoverflow 问题和他建议的解决方法。它确实有助于恢复（虽然需要几分钟），但问题会在一段时间后再次出现......
我也遇到了这个未解决的问题，并且使用建议的解决方法也恢复了问题，但问题又回来了。另外，这不完全是我的情况，在找到解决方法后问题就解决了......：\
技术细节：
kubeadm version: version.Info{Major:"1", Minor:"6+", GitVersion:"v1.6.0-alpha.0.2074+a092d8e0f95f52", GitCommit:"a092d8e0f95f5200f7ae2cba45c75ab42da36537", GitTreeState:"clean", BuildDate:"2016-12-13T17:03:18Z", GoVersion:"go1.7.4", Compiler:"gc", Platform:"linux/amd64"}
Kubernetes Version: version.Info{Major:"1", Minor:"5", GitVersion:"v1.5.3", GitCommit:"029c3a408176b55c30846f0faedf56aae5992e9b", GitTreeState:"clean", BuildDate:"2017-02-15T06:34:56Z", GoVersion:"go1.7.4", Compiler:"gc", Platform:"linux/amd64"}
使用以下命令启动集群：
kubeadm init --pod-network-cidr 10.244.0.0/16 --api-advertise-addresses 192.168.1.200
kubectl taint nodes --all dedicated-
kubectl -n kube-system apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml
一些可能相关的 syslog 日志（我有很多）：
Feb 23 11:07:49 server-03 kernel: [ 155.480669] IPv6: ADDRCONF(NETDEV_UP): eth0: link is not ready
Feb 23 11:07:49 server-03 dockerd[1414]: time="2017-02-23T11:07:49.735590817+02:00" level=warning msg="Couldn't run auplink before unmount /var/lib/docker/aufs/mnt/89bb7abdb946d858e175d80d6e1d2fdce0262af8c7afa9c6ad9d776f1f5028c4-init: exec: \"auplink\": executable file not found in $PATH"
Feb 23 11:07:49 server-03 kernel: [ 155.496599] aufs au_opts_verify:1597:dockerd[24704]: dirperm1 breaks the protection by the permission bits on the lower branch
Feb 23 11:07:49 server-03 systemd-udevd[29313]: Could not generate persistent MAC address for vethd4d85eac: No such file or directory
Feb 23 11:07:49 server-03 kubelet[1228]: E0223 11:07:49.756976 1228 cni.go:255] Error adding network: no IP addresses available in network: cbr0
Feb 23 11:07:49 server-03 kernel: [ 155.514994] IPv6: eth0: IPv6 duplicate address fe80::835:deff:fe4f:c74d detected!
Feb 23 11:07:49 server-03 kernel: [ 155.515380] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
Feb 23 11:07:49 server-03 kernel: [ 155.515588] device vethd4d85eac entered promiscuous mode
Feb 23 11:07:49 server-03 kernel: [ 155.515643] cni0: port 34(vethd4d85eac) entered forwarding state
Feb 23 11:07:49 server-03 kernel: [ 155.515663] cni0: port 34(vethd4d85eac) entered forwarding state
Feb 23 11:07:49 server-03 kubelet[1228]: E0223 11:07:49.757001 1228 cni.go:209] Error while adding to cni network: no IP addresses available in network: cbr0
Feb 23 11:07:49 server-03 kubelet[1228]: E0223 11:07:49.757056 1228 docker_manager.go:2201] Failed to setup network for pod "somepod-752955044-58g59_somenamespace(5d6c28e1-f8dd-11e6-9843-0cc47a9a5cf2)" using network plugins "cni": no IP addresses available in network: cbr0; Skipping pod
非常感谢！
编辑：
我能够重现它。这似乎是 kubelet CIDR 中 IP 地址的耗尽。发现：
首先，节点的 podCIDR 是（通过
kubectl get node -o yaml）：（podCIDR: 10.244.0.0/24顺便说一句，为什么不 /16 作为我在 kubeadm commnad 中设置的集群 CIDR？）。第二：
$ sudo ls -la /var/lib/cni/networks/cbr0 | wc -l256（也就是分配了256个IP吧？）但是，尽管我目前运行的 Kubernetes pod 和服务不超过 256 个，但还是会发生这种情况：
$ kubectl get all --all-namespaces | wc -l180### (Yes, this includes not only pods and services, but also jobs, deployments and replicasets)
那么，家里来的IP地址都用完了吗？如何解决？不可能这些解决方法是唯一的方法......
再次感谢。
编辑 (2)
另一个相关问题：https ://github.com/containernetworking/cni/issues/306