flannel pods in CrashLoopBackoff Error in kubernetes - kubernetes

Question

Using flannel as a CNI in kubernetes i am trying to implement a network for pod to pod communication spread on different vagrant vms. I am using this https://raw.githubusercontent.com/coreos/flannel/v0.9.0/Documentation/kube-flannel.yml to create flannel pods. But the kube-flannel pods go in CrashLoopBackOff error and do not start.
[root#flnode-04 ~]# kubectl get pods -o wide --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE IP NODE
diamanti-system collectd-v0.5-flnode-04 1/1 Running 0 3h 192.168.30.14 flnode-04
diamanti-system collectd-v0.5-flnode-05 1/1 Running 0 3h 192.168.30.15 flnode-05
diamanti-system collectd-v0.5-flnode-06 1/1 Running 0 3h 192.168.30.16 flnode-06
diamanti-system provisioner-d4kvf 1/1 Running 0 3h 192.168.30.16 flnode-06
kube-system kube-flannel-ds-2kqpv 0/1 CrashLoopBackOff 1 18m 192.168.30.14 flnode-04
kube-system kube-flannel-ds-xgqdm 0/1 CrashLoopBackOff 1 18m 192.168.30.16 flnode-06
kube-system kube-flannel-ds-z59jz 0/1 CrashLoopBackOff 1 18m 192.168.30.15 flnode-05
here are the logs of one pod
[root#flnode-04 ~]# kubectl logs kube-flannel-ds-2kqpv --namespace=kube-system
I0327 10:28:44.103425 1 main.go:483] Using interface with name mgmt0 and address 192.168.30.14
I0327 10:28:44.105609 1 main.go:500] Defaulting external address to interface address (192.168.30.14)
I0327 10:28:44.138132 1 kube.go:130] Waiting 10m0s for node controller to sync
I0327 10:28:44.138213 1 kube.go:283] Starting kube subnet manager
I0327 10:28:45.138509 1 kube.go:137] Node controller sync successful
I0327 10:28:45.138588 1 main.go:235] Created subnet manager: Kubernetes Subnet Manager - flnode-04
I0327 10:28:45.138596 1 main.go:238] Installing signal handlers
I0327 10:28:45.138690 1 main.go:348] Found network config - Backend type: vxlan
I0327 10:28:45.138767 1 vxlan.go:119] VXLAN config: VNI=1 Port=0 GBP=false DirectRouting=false
panic: assignment to entry in nil map
goroutine 1 [running]:
github.com/coreos/flannel/subnet/kube.(*kubeSubnetManager).AcquireLease(0xc420010cd0, 0x7f5314399bd0, 0xc420347880, 0xc4202213e0, 0x6, 0xf54, 0xc4202213e0)
/go/src/github.com/coreos/flannel/subnet/kube/kube.go:239 +0x1f7
github.com/coreos/flannel/backend/vxlan.(*VXLANBackend).RegisterNetwork(0xc4200b3480, 0x7f5314399bd0, 0xc420347880, 0xc420010c30, 0xc4200b3480, 0x0, 0x0, 0x4d0181)
/go/src/github.com/coreos/flannel/backend/vxlan/vxlan.go:141 +0x44e
main.main()
/go/src/github.com/coreos/flannel/main.go:278 +0x8ae
What exactly is the reason for flannel pods going into CrashLoopBackoff and what is the solution ?

Answer 1

I was able to solve the problem by running the command
kubectl annotate node appserv9 flannel.alpha.coreos.com/public-ip=10.10.10.10 --overwrite=true
Reason for bug : nil map in the code(no key available)
it doesn't matter what ip you give but this command has to be run individually on all the nodes so that the above error does not have to assign to a nil map.

Answer 2

If you deploy cluster with kubeadm init --pod-network-cidr network/mask, this network/mask should match the ConfigMap in kube-flannel.yaml
My ConfigMap looks like:
kind: ConfigMap
apiVersion: v1
metadata:
name: kube-flannel-cfg
namespace: kube-system
data:
...
net-conf.json: |
{
"Network": "10.244.0.0/16",
"Backend": {
"Type": "vxlan"
}
}
So the network/mask should equal 10.244.0.0/16