Deploying External OpenStack Cloud Provider with Kubeadm
This document describes how to install a single control-plane Kubernetes cluster v1.15 with kubeadm on CentOS, and then deploy an external OpenStack cloud provider and Cinder CSI plugin to use Cinder volumes as persistent volumes in Kubernetes.
Preparation in OpenStack
This cluster runs on OpenStack VMs, so let's create a few things in OpenStack first.
- A project/tenant for this Kubernetes cluster
- A user in this project for Kubernetes, to query node information and attach volumes etc
- A private network and subnet
- A router for this private network and connect it to a public network for floating IPs
- A security group for all Kubernetes VMs
- A VM as a control-plane node and a few VMs as worker nodes
The security group will have the following rules to open ports for Kubernetes.
Control-Plane Node
| Protocol | Port Number | Description |
|---|---|---|
| TCP | 6443 | Kubernetes API Server |
| TCP | 2379-2380 | etcd server client API |
| TCP | 10250 | Kubelet API |
| TCP | 10251 | kube-scheduler |
| TCP | 10252 | kube-controller-manager |
| TCP | 10255 | Read-only Kubelet API |
Worker Nodes
| Protocol | Port Number | Description |
|---|---|---|
| TCP | 10250 | Kubelet API |
| TCP | 10255 | Read-only Kubelet API |
| TCP | 30000-32767 | NodePort Services |
CNI ports on both control-plane and worker nodes
| Protocol | Port Number | Description |
|---|---|---|
| TCP | 179 | Calico BGP network |
| TCP | 9099 | Calico felix (health check) |
| UDP | 8285 | Flannel |
| UDP | 8472 | Flannel |
| TCP | 6781-6784 | Weave Net |
| UDP | 6783-6784 | Weave Net |
CNI specific ports are only required to be opened when that particular CNI plugin is used. In this guide, we will use Weave Net. Only the Weave Net ports (TCP 6781-6784 and UDP 6783-6784), will need to be opened in the security group.
The control-plane node needs at least 2 cores and 4GB RAM. After the VM is launched, verify its hostname and make sure it is the same as the node name in Nova.
If the hostname is not resolvable, add it to /etc/hosts.
For example, if the VM is called master1, and it has an internal IP 192.168.1.4. Add that to /etc/hosts and set hostname to master1.
echo "192.168.1.4 master1" >> /etc/hosts
hostnamectl set-hostname master1
Install Docker and Kubernetes
Next, we'll follow the official documents to install docker and Kubernetes using kubeadm.
Install Docker following the steps from the container runtime documentation.
Note that it is a best practice to use systemd as the cgroup driver for Kubernetes. If you use an internal container registry, add them to the docker config.
# Install Docker CE
## Set up the repository
### Install required packages.
yum install yum-utils device-mapper-persistent-data lvm2
### Add Docker repository.
yum-config-manager \
--add-repo \
https://download.docker.com/linux/centos/docker-ce.repo
## Install Docker CE.
yum update && yum install docker-ce-18.06.2.ce
## Create /etc/docker directory.
mkdir /etc/docker
# Configure the Docker daemon
cat > /etc/docker/daemon.json <<EOF
{
"exec-opts": ["native.cgroupdriver=systemd"],
"log-driver": "json-file",
"log-opts": {
"max-size": "100m"
},
"storage-driver": "overlay2",
"storage-opts": [
"overlay2.override_kernel_check=true"
]
}
EOF
mkdir -p /etc/systemd/system/docker.service.d
# Restart Docker
systemctl daemon-reload
systemctl restart docker
systemctl enable docker
Install kubeadm following the steps from the Installing Kubeadm documentation.
cat <<EOF > /etc/yum.repos.d/kubernetes.repo
[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
EOF
# Set SELinux in permissive mode (effectively disabling it)
# Caveat: In a production environment you may not want to disable SELinux, please refer to Kubernetes documents about SELinux
setenforce 0
sed -i 's/^SELINUX=enforcing$/SELINUX=permissive/' /etc/selinux/config
yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
systemctl enable --now kubelet
cat <<EOF > /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
EOF
sysctl --system
# check if br_netfilter module is loaded
lsmod | grep br_netfilter
# if not, load it explicitly with
modprobe br_netfilter
The official document about how to create a single control-plane cluster can be found from the Creating a single control-plane cluster with kubeadm documentation.
We'll largely follow that document but also add additional things for the cloud provider.
To make things more clear, we'll use a kubeadm-config.yml for the control-plane node.
In this config we specify to use an external OpenStack cloud provider, and where to find its config.
We also enable storage API in API server's runtime config so we can use OpenStack volumes as persistent volumes in Kubernetes.
apiVersion: kubeadm.k8s.io/v1beta1
kind: InitConfiguration
nodeRegistration:
kubeletExtraArgs:
cloud-provider: "external"
---
apiVersion: kubeadm.k8s.io/v1beta2
kind: ClusterConfiguration
kubernetesVersion: "v1.15.1"
apiServer:
extraArgs:
enable-admission-plugins: NodeRestriction
runtime-config: "storage.k8s.io/v1=true"
controllerManager:
extraArgs:
external-cloud-volume-plugin: openstack
extraVolumes:
- name: "cloud-config"
hostPath: "/etc/kubernetes/cloud-config"
mountPath: "/etc/kubernetes/cloud-config"
readOnly: true
pathType: File
networking:
serviceSubnet: "10.96.0.0/12"
podSubnet: "10.224.0.0/16"
dnsDomain: "cluster.local"
Now we'll create the cloud config, /etc/kubernetes/cloud-config, for OpenStack.
Note that the tenant here is the one we created for all Kubernetes VMs in the beginning.
All VMs should be launched in this project/tenant.
In addition you need to create a user in this tenant for Kubernetes to do queries.
The ca-file is the CA root certificate for OpenStack's API endpoint, for example https://openstack.cloud:5000/v3
At the time of writing the cloud provider doesn't allow insecure connections (skip CA check).
[Global]
region=RegionOne
username=username
password=password
auth-url=https://openstack.cloud:5000/v3
tenant-id=14ba698c0aec4fd6b7dc8c310f664009
domain-id=default
ca-file=/etc/kubernetes/ca.pem
[LoadBalancer]
subnet-id=b4a9a292-ea48-4125-9fb2-8be2628cb7a1
floating-network-id=bc8a590a-5d65-4525-98f3-f7ef29c727d5
[BlockStorage]
bs-version=v2
[Networking]
public-network-name=public
ipv6-support-disabled=false
Next run kubeadm to initiate the control-plane node
kubeadm init --config=kubeadm-config.yml
With the initialization completed, copy admin config to .kube
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
At this stage, the control-plane node is created but not ready. All the nodes have the taint node.cloudprovider.kubernetes.io/uninitialized=true:NoSchedule and are waiting to be initialized by the cloud-controller-manager.
# kubectl describe no master1
Name: master1
Roles: master
......
Taints: node-role.kubernetes.io/master:NoSchedule
node.cloudprovider.kubernetes.io/uninitialized=true:NoSchedule
node.kubernetes.io/not-ready:NoSchedule
......
Now deploy the OpenStack cloud controller manager into the cluster, following .
Create a secret with the cloud-config for the openstack cloud provider.
kubectl create secret -n kube-system generic cloud-config --from-literal=cloud.conf="$(cat /etc/kubernetes/cloud-config)" --dry-run -o yaml > cloud-config-secret.yaml
kubectl apply -f cloud-config-secret.yaml
Get the CA certificate for OpenStack API endpoints and put that into /etc/kubernetes/ca.pem.
Create RBAC resources.
kubectl apply -f https://github.com/kubernetes/cloud-provider-openstack/raw/release-1.15/cluster/addons/rbac/cloud-controller-manager-roles.yaml
kubectl apply -f https://github.com/kubernetes/cloud-provider-openstack/raw/release-1.15/cluster/addons/rbac/cloud-controller-manager-role-bindings.yaml
We'll run the OpenStack cloud controller manager as a DaemonSet rather than a pod.
The manager will only run on the control-plane node, so if there are multiple control-plane nodes, multiple pods will be run for high availability.
Create openstack-cloud-controller-manager-ds.yaml containing the following manifests, then apply it.
---
apiVersion: v1
kind: ServiceAccount
metadata:
name: cloud-controller-manager
namespace: kube-system
---
apiVersion: apps/v1
kind: DaemonSet
metadata:
name: openstack-cloud-controller-manager
namespace: kube-system
labels:
k8s-app: openstack-cloud-controller-manager
spec:
selector:
matchLabels:
k8s-app: openstack-cloud-controller-manager
updateStrategy:
type: RollingUpdate
template:
metadata:
labels:
k8s-app: openstack-cloud-controller-manager
spec:
nodeSelector:
node-role.kubernetes.io/master: ""
securityContext:
runAsUser: 1001
tolerations:
- key: node.cloudprovider.kubernetes.io/uninitialized
value: "true"
effect: NoSchedule
- key: node-role.kubernetes.io/master
effect: NoSchedule
- effect: NoSchedule
key: node.kubernetes.io/not-ready
serviceAccountName: cloud-controller-manager
containers:
- name: openstack-cloud-controller-manager
image: docker.io/k8scloudprovider/openstack-cloud-controller-manager:v1.15.0
args:
- /bin/openstack-cloud-controller-manager
- --v=1
- --cloud-config=$(CLOUD_CONFIG)
- --cloud-provider=openstack
- --use-service-account-credentials=true
- --address=127.0.0.1
volumeMounts:
- mountPath: /etc/kubernetes/pki
name: k8s-certs
readOnly: true
- mountPath: /etc/ssl/certs
name: ca-certs
readOnly: true
- mountPath: /etc/config
name: cloud-config-volume
readOnly: true
- mountPath: /usr/libexec/kubernetes/kubelet-plugins/volume/exec
name: flexvolume-dir
- mountPath: /etc/kubernetes
name: ca-cert
readOnly: true
resources:
requests:
cpu: 200m
env:
- name: CLOUD_CONFIG
value: /etc/config/cloud.conf
hostNetwork: true
volumes:
- hostPath:
path: /usr/libexec/kubernetes/kubelet-plugins/volume/exec
type: DirectoryOrCreate
name: flexvolume-dir
- hostPath:
path: /etc/kubernetes/pki
type: DirectoryOrCreate
name: k8s-certs
- hostPath:
path: /etc/ssl/certs
type: DirectoryOrCreate
name: ca-certs
- name: cloud-config-volume
secret:
secretName: cloud-config
- name: ca-cert
secret:
secretName: openstack-ca-cert
When the controller manager is running, it will query OpenStack to get information about the nodes and remove the taint. In the node info you'll see the VM's UUID in OpenStack.
# kubectl describe no master1
Name: master1
Roles: master
......
Taints: node-role.kubernetes.io/master:NoSchedule
node.kubernetes.io/not-ready:NoSchedule
......
sage:docker: network plugin is not ready: cni config uninitialized
......
PodCIDR: 10.224.0.0/24
ProviderID: openstack:///548e3c46-2477-4ce2-968b-3de1314560a5
Now install your favourite CNI and the control-plane node will become ready.
For example, to install Weave Net, run this command:
kubectl apply -f "https://cloud.weave.works/k8s/net?k8s-version=$(kubectl version | base64 | tr -d '\n')"
Next we'll set up worker nodes.
Firstly, install docker and kubeadm in the same way as how they were installed in the control-plane node. To join them to the cluster we need a token and ca cert hash from the output of control-plane node installation. If it is expired or lost we can recreate it using these commands.
# check if token is expired
kubeadm token list
# re-create token and show join command
kubeadm token create --print-join-command
Create kubeadm-config.yml for worker nodes with the above token and ca cert hash.
apiVersion: kubeadm.k8s.io/v1beta2
discovery:
bootstrapToken:
apiServerEndpoint: 192.168.1.7:6443
token: 0c0z4p.dnafh6vnmouus569
caCertHashes: ["sha256:fcb3e956a6880c05fc9d09714424b827f57a6fdc8afc44497180905946527adf"]
kind: JoinConfiguration
nodeRegistration:
kubeletExtraArgs:
cloud-provider: "external"
apiServerEndpoint is the control-plane node, token and caCertHashes can be taken from the join command printed in the output of 'kubeadm token create' command.
Run kubeadm and the worker nodes will be joined to the cluster.
kubeadm join --config kubeadm-config.yml
At this stage we'll have a working Kubernetes cluster with an external OpenStack cloud provider. The provider tells Kubernetes about the mapping between Kubernetes nodes and OpenStack VMs. If Kubernetes wants to attach a persistent volume to a pod, it can find out which OpenStack VM the pod is running on from the mapping, and attach the underlying OpenStack volume to the VM accordingly.