Version 1.12. This version is no longer supported. For information about how to upgrade to version 1.13, see Upgrading Anthos on bare metal in the 1.13 documentation. For more information about supported and unsupported versions, see the Version history page in the latest documentation.

Create user clusters in a multi-cluster setup

In Google Distributed Cloud, user clusters run your workloads, and in a multi-cluster architecture, user clusters are created and managed by an admin cluster.

Once you've created an admin cluster, calling the bmctl create config command creates a YAML file you can edit to define your user cluster. To apply the configuration and create the user cluster, use the bmctl create cluster command. Preflight checks are applicable to the user clusters created with bmctl create cluster command.

Keeping workloads off the admin cluster protects sensitive administrative data, like SSH keys stored in the admin cluster, from those who don't need access to that information. Additionally, keeping user clusters separate from each other provides good general security for your workloads.

Prerequisites

Latest bmctl is downloaded (gs://anthos-baremetal-release/bmctl/1.12.9/linux-amd64/bmctl) from Cloud Storage.
Working admin cluster with access to the cluster API server (the controlPlaneVIP).
Admin cluster nodes have network connectivity to all nodes on the target user cluster.
Workstation running bmctl has network connectivity to all nodes in the target user clusters.
SSH key used to create user cluster available to root or SUDO user on all nodes in the user cluster.
Connect-register service account is configured on the admin cluster for use with Connect.

Enable SELinux

If you want to enable SELinux to secure your containers, you must make sure that SELinux is enabled in Enforced mode on all your host machines. Starting with Google Distributed Cloud release 1.9.0 or later, you can enable or disable SELinux before or after cluster creation or cluster upgrades. SELinux is enabled by default on Red Hat Enterprise Linux (RHEL) and CentOS. If SELinux is disabled on your host machines or you aren't sure, see Securing your containers using SELinux for instructions on how to enable it.

Google Distributed Cloud supports SELinux in only RHEL and CentOS systems.

Create a user cluster config file

The config file for creating a user cluster is almost exactly the same as the one used for creating an admin cluster. The only difference is that you remove the local credentials configuration section to make the config a valid collection of Kubernetes resources. The configuration section is at the top of the file under the bmctl configuration variables section. For examples of user cluster configurations, see User clusters in the Cluster configuration samples.

By default, user clusters inherit their credentials from the admin cluster that manages them. You can selectively override some or all of these credentials.

Create a user cluster config file with the bmctl create config command:
```
bmctl create config -c USER_CLUSTER_NAME
```
For example, issue the following to create a config file for a user cluster called user1:
```
bmctl create config -c user1
```
The file is written to bmctl-workspace/user1/user1.yaml. The generic path to the file is bmctl-workspace/CLUSTER NAME/CLUSTER_NAME.yaml.

Edit the config file with the following changes:

Remove the local credentials file paths from the config:

....
  gcrKeyPath: (path to GCR service account key)
  sshPrivateKeyPath: (path to SSH private key, used for node access)
  gkeConnectAgentServiceAccountKeyPath: (path to Connect agent service account key)
  gkeConnectRegisterServiceAccountKeyPath: (path to Hub registration service account key)
  cloudOperationsServiceAccountKeyPath: (path to Cloud Operations service account key)
....

Change the config to specify a cluster type of user instead of admin:

....
spec:
  # Cluster type. This can be:
  #   1) admin:  to create an admin cluster. This can later be used to create
  #   user clusters.
  #   2) user:   to create a user cluster. Requires an existing admin cluster.
  #   3) hybrid: to create a hybrid cluster that runs admin cluster
  #   components and user workloads.
  #   4) standalone: to create a cluster that manages itself, runs user
  #   workloads, but does not manage other clusters.
  type: user
....

Ensure the admin and user cluster specifications for the load balancer VIPs and address pools are complementary, and do not overlap existing clusters. A sample pair of admin and user cluster configurations, specifying load balancing and address pools, is shown below:

....
# Sample admin cluster config for load balancer and address pools
  loadBalancer:
    vips:
      controlPlaneVIP: 10.200.0.49
      ingressVIP: 10.200.0.50
    addressPools:
    - name: pool1
      addresses:
      - 10.200.0.50-10.200.0.70
....
....
# Sample user cluster config for load balancer and address pools
loadBalancer:
    vips:
      controlPlaneVIP: 10.200.0.71
      ingressVIP: 10.200.0.72
    addressPools:
    - name: pool1
      addresses:
      - 10.200.0.72-10.200.0.90
....

The rest of the user cluster config files are the same as the admin cluster config.

Specify the pod density of cluster nodes and the container runtime:
```
....
# NodeConfig specifies the configuration that applies to all nodes in the cluster.
nodeConfig:
  # podDensity specifies the pod density configuration.
  podDensity:
    # maxPodsPerNode specifies at most how many pods can be run on a single node.
    maxPodsPerNode: 110
  # containerRuntime specifies which container runtime to use for scheduling containers on nodes.
  # containerd and docker are supported.
  containerRuntime: containerd
....
```
For user clusters, allowable values for maxPodsPerNode are 32-250. The default value if unspecified is 110. Once the cluster is created, this value cannot be updated.

The default container runtime is containerd. Alternatively, you can use Docker. For more information about changing your runtime, see our Change your container runtime guide.

Pod density is also limited by your cluster's available IP resources. For details, see Pod networking.

Create the user cluster

Issue the bmctl command to apply the user cluster config and create the cluster:

bmctl create cluster -c USER_CLUSTER_NAME --kubeconfig ADMIN_KUBECONFIG

Replace the following:

USER_CLUSTER_NAME: the cluster name created in the previous section.
ADMIN_KUBECONFIG: the path to the admin cluster kubeconfig file.

For example, for a user cluster named user1, and an admin cluster kubeconfig file with the path kubeconfig bmctl-workspace/admin/admin-kubeconfig, the command would be:

bmctl create cluster -c user1 --kubeconfig bmctl-workspace/admin/admin-kubeconfig

Sample user cluster configurations

For example user cluster configurations, see User clusters in the Cluster configuration samples.