kubernetes installation and kube-dns: open /run/flannel/subnet.env: no such file or directory
Overview
kube-dns can't start (SetupNetworkError) after kubeadm init and network setup:
Error syncing pod, skipping: failed to "SetupNetwork" for
"kube-dns-654381707-w4mpg_kube-system" with SetupNetworkError:
"Failed to setup network for pod
\"kube-dns-654381707-w4mpg_kube-system(8ffe3172-a739-11e6-871f-000c2912631c)\"
using network plugins \"cni\": open /run/flannel/subnet.env:
no such file or directory; Skipping pod"
Kubernetes version
Client Version: version.Info{Major:"1", Minor:"4", GitVersion:"v1.4.4", GitCommit:"3b417cc4ccd1b8f38ff9ec96bb50a81ca0ea9d56", GitTreeState:"clean", BuildDate:"2016-10-21T02:48:38Z", GoVersion:"go1.6.3", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"4", GitVersion:"v1.4.4", GitCommit:"3b417cc4ccd1b8f38ff9ec96bb50a81ca0ea9d56", GitTreeState:"clean", BuildDate:"2016-10-21T02:42:39Z", GoVersion:"go1.6.3", Compiler:"gc", Platform:"linux/amd64"}
Environment
VMWare Fusion for Mac
OS
NAME="Ubuntu"
VERSION="16.04.1 LTS (Xenial Xerus)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 16.04.1 LTS"
VERSION_ID="16.04"
HOME_URL="http://www.ubuntu.com/"
SUPPORT_URL="http://help.ubuntu.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/ubuntu/"
VERSION_CODENAME=xenial
UBUNTU_CODENAME=xenial
Kernel (e.g. uname -a)
Linux ubuntu-master 4.4.0-47-generic #68-Ubuntu SMP Wed Oct 26 19:39:52 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux
What is the problem
kube-system kube-dns-654381707-w4mpg 0/3 ContainerCreating 0 2m
FirstSeen LastSeen Count From SubobjectPath Type Reason Message
--------- -------- ----- ---- ------------- -------- ------ -------
3m 3m 1 {default-scheduler } Normal Scheduled Successfully assigned kube-dns-654381707-w4mpg to ubuntu-master
2m 1s 177 {kubelet ubuntu-master} Warning FailedSync Error syncing pod, skipping: failed to "SetupNetwork" for "kube-dns-654381707-w4mpg_kube-system" with SetupNetworkError: "Failed to setup network for pod \"kube-dns-654381707-w4mpg_kube-system(8ffe3172-a739-11e6-871f-000c2912631c)\" using network plugins \"cni\": open /run/flannel/subnet.env: no such file or directory; Skipping pod"
What I expected to happen
kube-dns Running
How to reproduce it
root@ubuntu-master:~# kubeadm init
Running pre-flight checks
<master/tokens> generated token: "247a8e.b7c8c1a7685bf204"
<master/pki> generated Certificate Authority key and certificate:
Issuer: CN=kubernetes | Subject: CN=kubernetes | CA: true
Not before: 2016-11-10 11:40:21 +0000 UTC Not After: 2026-11-08 11:40:21 +0000 UTC
Public: /etc/kubernetes/pki/ca-pub.pem
Private: /etc/kubernetes/pki/ca-key.pem
Cert: /etc/kubernetes/pki/ca.pem
<master/pki> generated API Server key and certificate:
Issuer: CN=kubernetes | Subject: CN=kube-apiserver | CA: false
Not before: 2016-11-10 11:40:21 +0000 UTC Not After: 2017-11-10 11:40:21 +0000 UTC
Alternate Names: [172.20.10.4 10.96.0.1 kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local]
Public: /etc/kubernetes/pki/apiserver-pub.pem
Private: /etc/kubernetes/pki/apiserver-key.pem
Cert: /etc/kubernetes/pki/apiserver.pem
<master/pki> generated Service Account Signing keys:
Public: /etc/kubernetes/pki/sa-pub.pem
Private: /etc/kubernetes/pki/sa-key.pem
<master/pki> created keys and certificates in "/etc/kubernetes/pki"
<util/kubeconfig> created "/etc/kubernetes/kubelet.conf"
<util/kubeconfig> created "/etc/kubernetes/admin.conf"
<master/apiclient> created API client configuration
<master/apiclient> created API client, waiting for the control plane to become ready
<master/apiclient> all control plane components are healthy after 14.053453 seconds
<master/apiclient> waiting for at least one node to register and become ready
<master/apiclient> first node is ready after 0.508561 seconds
<master/apiclient> attempting a test deployment
<master/apiclient> test deployment succeeded
<master/discovery> created essential addon: kube-discovery, waiting for it to become ready
<master/discovery> kube-discovery is ready after 1.503838 seconds
<master/addons> created essential addon: kube-proxy
<master/addons> created essential addon: kube-dns
Kubernetes master initialised successfully!
You can now join any number of machines by running the following on each node:
kubeadm join --token=247a8e.b7c8c1a7685bf204 172.20.10.4
root@ubuntu-master:~#
root@ubuntu-master:~# kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system dummy-2088944543-eo1ua 1/1 Running 0 47s
kube-system etcd-ubuntu-master 1/1 Running 3 51s
kube-system kube-apiserver-ubuntu-master 1/1 Running 0 49s
kube-system kube-controller-manager-ubuntu-master 1/1 Running 3 51s
kube-system kube-discovery-1150918428-qmu0b 1/1 Running 0 46s
kube-system kube-dns-654381707-mv47d 0/3 ContainerCreating 0 44s
kube-system kube-proxy-k0k9q 1/1 Running 0 44s
kube-system kube-scheduler-ubuntu-master 1/1 Running 3 51s
root@ubuntu-master:~#
root@ubuntu-master:~# kubectl apply -f https://git.io/weave-kube
daemonset "weave-net" created
root@ubuntu-master:~#
root@ubuntu-master:~#
root@ubuntu-master:~# kubectl get pods --all-namespaces
NAMESPACE NAME READY STATUS RESTARTS AGE
kube-system dummy-2088944543-eo1ua 1/1 Running 0 47s
kube-system etcd-ubuntu-master 1/1 Running 3 51s
kube-system kube-apiserver-ubuntu-master 1/1 Running 0 49s
kube-system kube-controller-manager-ubuntu-master 1/1 Running 3 51s
kube-system kube-discovery-1150918428-qmu0b 1/1 Running 0 46s
kube-system kube-dns-654381707-mv47d 0/3 ContainerCreating 0 44s
kube-system kube-proxy-k0k9q 1/1 Running 0 44s
kube-system kube-scheduler-ubuntu-master 1/1 Running 3 51s
kube-system weave-net-ja736 2/2 Running 0 1h
Answer
It looks like you have configured flannel before running kubeadm init. You can try to fix this by removing flannel (it may be sufficient to remove config file rm -f /etc/cni/net.d/*flannel*), but it's best to start fresh.