Agfdhyk

Just I am starting to learn Kubernetes. I've installed CentOS 7.5 with SELinux disabled kubectl, kubeadm and kubelet by Kubernetes YUM repository.

However, when I want to start a kubeadm init command. I get this error message:

[init] using Kubernetes version: v1.12.2

[preflight] running pre-flight checks

    [WARNING Firewalld]: firewalld is active, please ensure ports [6443 10250] are open or your cluster may not function correctly

[preflight/images] Pulling images required for setting up a Kubernetes cluster

[preflight/images] This might take a minute or two, depending on the speed of your internet connection

[preflight/images] You can also perform this action in beforehand using 'kubeadm config images pull'

[kubelet] Writing kubelet environment file with flags to file "/var/lib/kubelet/kubeadm-flags.env"

[kubelet] Writing kubelet configuration to file "/var/lib/kubelet/config.yaml"

[preflight] Activating the kubelet service

[certificates] Generated front-proxy-ca certificate and key.

[certificates] Generated front-proxy-client certificate and key.

[certificates] Generated etcd/ca certificate and key.

[certificates] Generated etcd/peer certificate and key.

[certificates] etcd/peer serving cert is signed for DNS names [vps604805.ovh.net localhost] and IPs [51.75.201.75 127.0.0.1 ::1]

[certificates] Generated apiserver-etcd-client certificate and key.

[certificates] Generated etcd/server certificate and key.

[certificates] etcd/server serving cert is signed for DNS names [vps604805.ovh.net localhost] and IPs [127.0.0.1 ::1]

[certificates] Generated etcd/healthcheck-client certificate and key.

[certificates] Generated ca certificate and key.

[certificates] Generated apiserver certificate and key.

[certificates] apiserver serving cert is signed for DNS names [vps604805.ovh.net kubernetes kubernetes.default kubernetes.default.svc kubernetes.default.svc.cluster.local] and IPs [10.96.0.1 51.75.201.75]

[certificates] Generated apiserver-kubelet-client certificate and key.

[certificates] valid certificates and keys now exist in "/etc/kubernetes/pki"

[certificates] Generated sa key and public key.

[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/admin.conf"

[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/kubelet.conf"

[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/controller-manager.conf"

[kubeconfig] Wrote KubeConfig file to disk: "/etc/kubernetes/scheduler.conf"

[controlplane] wrote Static Pod manifest for component kube-apiserver to "/etc/kubernetes/manifests/kube-apiserver.yaml"

[controlplane] wrote Static Pod manifest for component kube-controller-manager to "/etc/kubernetes/manifests/kube-controller-manager.yaml"

[controlplane] wrote Static Pod manifest for component kube-scheduler to "/etc/kubernetes/manifests/kube-scheduler.yaml"

[etcd] Wrote Static Pod manifest for a local etcd instance to "/etc/kubernetes/manifests/etcd.yaml"

[init] waiting for the kubelet to boot up the control plane as Static Pods from directory "/etc/kubernetes/manifests" 

[init] this might take a minute or longer if the control plane images have to be pulled

[apiclient] All control plane components are healthy after 26.003496 seconds

[uploadconfig] storing the configuration used in ConfigMap "kubeadm-config" in the "kube-system" Namespace

[kubelet] Creating a ConfigMap "kubelet-config-1.12" in namespace kube-system with the configuration for the kubelets in the cluster

[markmaster] Marking the node vps604805.ovh.net as master by adding the label "node-role.kubernetes.io/master=''"

[markmaster] Marking the node vps604805.ovh.net as master by adding the taints [node-role.kubernetes.io/master:NoSchedule]

error marking master: timed out waiting for the condition

According to Linux Foundation course, I don't need more command to execute to create my first start cluster into my VM.

Wrong?

Firewalld does have open ports into firewall. 6443/tcp and 10248-10252

I would recommend to bootstrap Kubernetes cluster as guided in the official documentation. I've proceeded with some steps to build cluster on the same CentOS version CentOS Linux release 7.5.1804 (Core) and will share them with you, hope it can be helpful to you to get rid of the issue during installation.

First wipe your current cluster installation:

# kubeadm reset -f && rm -rf /etc/kubernetes/

Add Kubernetes repo for further kubeadm, kubelet, kubectl installation:

[kubernetes]

name=Kubernetes

baseurl=https://packages.cloud.google.com/yum/repos/kubernetes-el7-x86_64

enabled=1

gpgcheck=1

repo_gpgcheck=1

gpgkey=https://packages.cloud.google.com/yum/doc/yum-key.gpg https://packages.cloud.google.com/yum/doc/rpm-package-key.gpg

exclude=kube*

EOF

Check whether SELinux is in permissive mode:

# getenforce

Permissive

Ensure net.bridge.bridge-nf-call-iptables is set to 1 in your sysctl:

# cat <<EOF >  /etc/sysctl.d/k8s.conf

net.bridge.bridge-nf-call-ip6tables = 1

net.bridge.bridge-nf-call-iptables = 1

EOF

sysctl --system

Install required Kubernetes components and start services:

# yum update && yum upgrade && yum install -y docker kubelet kubeadm kubectl --disableexcludes=kubernetes



# systemctl start docker kubelet && systemctl enable docker kubelet

Deploy the cluster via kubeadm:

kubeadm init --pod-network-cidr=10.244.0.0/16

I prefer to install Flannel as the main CNI in my cluster, although there are some prerequisites for proper Pod network installation, I've passed --pod-network-cidr=10.244.0.0/16 flag to kubeadm init command.

Create Kubernetes Home directory for your user and store config file:

$ mkdir -p $HOME/.kube

$ sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config

$ sudo chown $(id -u):$(id -g) $HOME/.kube/config

Install Pod network, in my case it was Flannel:

$ kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/bc79dd1505b0c8681ece4de4c0d86c5cd2643275/Documentation/kube-flannel.yml

Finally check Kubernetes core Pods status:

$ kubectl get pods --all-namespaces

NAMESPACE     NAME                                 READY   STATUS    RESTARTS   AGE

kube-system   coredns-576cbf47c7-4x7zq             1/1     Running   0          36m

kube-system   coredns-576cbf47c7-666jm             1/1     Running   0          36m

kube-system   etcd-centos-7-5                      1/1     Running   0          35m

kube-system   kube-apiserver-centos-7-5            1/1     Running   0          35m

kube-system   kube-controller-manager-centos-7-5   1/1     Running   0          35m

kube-system   kube-flannel-ds-amd64-2bmw9          1/1     Running   0          33m

kube-system   kube-proxy-pcgw8                     1/1     Running   0          36m

kube-system   kube-scheduler-centos-7-5            1/1     Running   0          35m

In case you still have any doubts, just write down a comment below this answer.

You are hitting the following issue in kubernetes

https://github.com/kubernetes/kubeadm/issues/1092

The workaround is to provide --node-name=<hostname> . Just go through the above ticket for more info. Hope this helps

EDIT:
I have the same issue in kubeadm-1.10.0
After removing --hostname-override from /etc/systemd/system/kubelet.service.d/10-kubeadm.conf file, atleast able to initialize cluster. Didn't give provide --node-name in my cluster