This document describes how a new seed cluster can be added to an existing KKP master cluster.
For smaller scale setups it’s possible to use the existing master cluster as a seed cluster (a “shared” cluster installation). In this case both master and seed components will run on the same cluster and in the same namespace. It is however not possible to use the same cluster for multiple seeds.
Please refer to the architecture diagrams for more information about the cluster relationships.
The setup procedure for seed clusters happens in multiple stages:
Seed resource on the master cluster.Seed cluster is valid and installs the KKP components like the
seed-controller-manager. This is an automated process.KKP performs regular backups of user clusters by snapshotting the etcd of each cluster. The default configuration
uses in-cluster object storage provided by Minio. It can be installed using minio Helm chart
provided with the KKP installer.
If you wish to use a different S3-compatible solution for storage of backups, it can be configured within the
KubermaticConfiguration object. Refer to the
KubermaticConfiguration documentation for an example
of the .spec.backup fields and values. The following content assumes you’re using the provided minio Helm chart.
Minio requires a storage class which will be used as a backend for the exposed object storage. You can view the storage classes available on the cluster using the following command:
kubectl get storageclasses
#NAME PROVISIONER AGE
#kubermatic-fast kubernetes.io/aws-ebs 195d
#kubermatic-backup kubernetes.io/aws-ebs 195d
#standard (default) kubernetes.io/aws-ebs 2y43d
It’s recommended that Minio uses a separate storage class with a different location/security level, but you can also use the default one if you desire.
As Minio does not require any of the SSD’s advantages, we can use HDD-backed storage. It’s recommended that Minio uses a separate storage class with a different location/security level. For a cluster running on AWS, an example class could look as follows:
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: kubermatic-backup
provisioner: kubernetes.io/aws-ebs
parameters:
type: sc1
To configure the storage class to use and the size of backing storage, edit minio section in your values.yaml file.
For more information about the Minio options, take a look at
minio chart values.yaml and the
min.io documentation - S3 gateway.
minio:
storeSize: '200Gi'
# specified storageClass will be used as a storage provider for minio
# which will be used store the etcd backup of the seed hosted user clusters
storageClass: kubermatic-backup
# access key/secret for the exposed minio S3 gateway
credentials:
# generated access key length should be at least 3 characters
accessKey: "YOUR-ACCESS-KEY"
# generated secret key length should be at least 8 characters
secretKey: "YOUR-SECRET-KEY"
As a good practice, we also recommend installing the s3-exporter Helm chart, which provides metrics regarding user
cluster backups.
The Kubermatic Installler is the recommended way to setup new seed clusters. A manual installation is possible, however more work needs to be done.
Similar to how the master cluster can be installed with the installler, run the deploy command. You still need to
manually ensure that the StorageClass you configured for Minio exists already.
export KUBECONFIG=/path/to/seed-cluster/kubeconfig
./kubermatic-installer deploy kubermatic-seed --config kubermatic.yaml --helm-values values.yaml
The command above will take care of installing/updating the CRDs, setting up Minio and the S3-exporter and attempts to provide you with the necessary DNS settings after the installation has completed.
Once the installer has completed, check the kubermatic namespace on the seed cluster, where the new controller managers
should be deployed automatically. If the deployment gets stuck, check the kubermatic-operator logs on the master
cluster.
Once the preparation for the cluster backup are done (setting up the StorageClass), install the Kubermatic CRDs using kubectl. The charts directory is part of the download archive on GitHub. Run the following command on the seed cluster:
kubectl replace -f charts/kubermatic-operator/crd/
After configuring the required options, you can install the charts:
helm --namespace minio upgrade --install --wait --values /path/to/your/helm-values.yaml minio charts/minio/
helm --namespace kube-system upgrade --install --wait --values /path/to/your/helm-values.yaml s3-exporter charts/s3-exporter/
To connect the new seed cluster with the master, you need to create a kubeconfig Secret and a Seed resource on the master cluster. This allows the KKP components in the master cluster to communicate with the seed cluster and reconcile user-cluster control planes.
To make sure that the kubeconfig stays valid forever, it must not contain temporary login tokens. Depending on the
cloud provider, the default kubeconfig that is provided may not contain username+password / a client certificate, but instead
try to talk to local token helper programs like aws-iam-authenticator for AWS or gcloud for the Google Cloud (GKE).
These kubeconfig files will not work for setting up Seeds.
The kubermatic-installer tool provides a command convert-kubeconfig that can be used to prepare a kubeconfig for
usage in Kubermatic. The script will create a ServiceAccount in the seed cluster, bind it to the cluster-admin role
and then put the ServiceAccount’s token into the kubeconfig file. Afterwards the file can be used in KKP.
./kubermatic-installer convert-kubeconfig <ORIGINAL-KUBECONFIG-FILE> > my-kubeconfig-file
The Seed resource itself needs to be called kubermatic (for the Community Edition) and needs to reference the new
kubeconfig Secret like so:
apiVersion: v1
kind: Secret
metadata:
name: kubeconfig-kubermatic
namespace: kubermatic
type: Opaque
data:
# You can use `base64 -w0 my-kubeconfig-file` to encode the
# kubeconfig properly for inserting into this Secret.
kubeconfig: <base64 encoded kubeconfig>
---
apiVersion: kubermatic.k8c.io/v1
kind: Seed
metadata:
# The Seed *must* be named "kubermatic".
name: kubermatic
namespace: kubermatic
spec:
# these two fields are only informational
country: DE
location: Hamburg
# list of datacenters where this seed cluster is allowed to create clusters in
datacenters: {}
# reference to the kubeconfig to use when connecting to this seed cluster
kubeconfig:
name: kubeconfig-kubermatic
namespace: kubermatic
Refer to the Seed CRD documentation for a complete example of the Seed CustomResource and all possible datacenters. ¹ You can override the global Expose Strategy at Seed level if you wish to.
Apply the manifest above in the master cluster and KKP will pick up the new Seed and begin to reconcile it by installing the
required KKP components. You can watch the progress by using kubectl and watch:
kubectl apply -f seed-with-secret.yaml
#Secret/kubeconfig-kubermatic created.
#Seed/kubermatic created.
watch kubectl -n kubermatic get pods
#NAME READY STATUS RESTARTS AGE
#kubermatic-api-55765568f7-br9jl 1/1 Running 0 5m4s
#kubermatic-api-55765568f7-xbvz2 1/1 Running 0 5m13s
#kubermatic-dashboard-5d784d586b-f46f8 1/1 Running 0 35m
#kubermatic-dashboard-5d784d586b-rgl29 1/1 Running 0 35m
#kubermatic-master-controller-manager-f58d4df59-w7rkz 1/1 Running 0 5m13s
#kubermatic-operator-7f6957869d-89g55 1/1 Running 0 5m37s
#nodeport-proxy-envoy-6d8bb6fbff-9z57l 2/2 Running 0 5m6s
#nodeport-proxy-envoy-6d8bb6fbff-dl58l 2/2 Running 0 4m54s
#nodeport-proxy-envoy-6d8bb6fbff-k4gp8 2/2 Running 0 4m44s
#nodeport-proxy-updater-7fd55f948-cll8n 1/1 Running 0 4m44s
#seed-proxy-kubermatic-6dd5cc95cf-r6wvb 1/1 Running 0 80m
If you experience issues with the seed cluster setup, for example nothing happening in the kubermatic namespace,
check the Kubermatic Operator’s logs on the master cluster, for example via kubectl --namespace kubermatic logs -f kubermatic-operator-7f6957869d-89g55.
Depending on the chosen Expose Strategy, the control planes of all user clusters
running in the Seed cluster will be exposed by the nodeport-proxy or using services of type NodePort directly.
By default each user cluster gets a virtual domain name like [cluster-id].[seed-name].[kubermatic-domain], e.g.
hdu328tr.kubermatic.kubermatic.example.com for the Seed from the previous step with kubermatic.example.com being the main domain
where the KKP dashboard/API are available.
A wildcard DNS record *.[seed-name].[kubermatic-domain] must be created. The target of the DNS wildcard record should be the
EXTERNAL-IP of the nodeport-proxy service in the kubermatic namespace or a set of seed nodes IPs.
When your cloud provider supports LoadBalancers, you can find the target IP / hostname by looking at the
nodeport-proxy Service:
kubectl -n kubermatic get services
#NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
#nodeport-proxy LoadBalancer 10.47.248.232 8.7.6.5 80:32014/TCP,443:30772/TCP 449d
The EXTERNAL-IP is what we need to put into the DNS record.
Without a LoadBalancer, you will need to point to one or many of the seed cluster’s nodes. You can get a list of external IPs like so:
kubectl get nodes -o wide
#NAME STATUS ROLES AGE VERSION INTERNAL-IP EXTERNAL-IP
#worker-node-cbd686cd-50nx Ready <none> 3h36m v1.15.8-gke.3 10.156.0.36 8.7.6.4
#worker-node-cbd686cd-59s2 Ready <none> 21m v1.15.8-gke.3 10.156.0.14 8.7.6.3
#worker-node-cbd686cd-90j3 Ready <none> 45m v1.15.8-gke.3 10.156.0.22 8.7.6.2
Create an A or CNAME record as needed pointing to the target:
*.kubermatic.kubermatic.example.com. IN A 8.7.6.5
or, for a CNAME:
*.kubermatic.kubermatic.example.com. IN CNAME myloadbalancer.example.com.