Creating admin clusters in a multi-cluster setup

In GKE on Bare Metal, you set up admin clusters to manage other clusters securely. You can create, update, upgrade, or delete user clusters from admin clusters. The user clusters run workloads separately from administration, so sensitive information is protected.

Admin clusters managing multi-cluster workloads can provide highly available (HA) reliability. In a HA cluster, if one control plane node fails, other nodes will continue to work.

An admin cluster in a multi-cluster environment provides the best fundamental security. Because access to administration data is separated from workloads, those who access user workloads have no access to sensitive administrative data, like SSH keys and service account data. As a result, there is some trade-off between security and the resources required, since a separate admin cluster means you need dedicated resources for management and workloads.

You create an admin cluster using the bmctl command. After you create an admin cluster, you create user clusters to run workloads.

Prerequisites:

  • Download bmctl from gs://anthos-baremetal-release/bmctl/1.6.2/linux-amd64/bmctl
  • The workstation running bmctl should have network connectivity to all nodes in the target user clusters.
  • The workstation running bmctl should have network connectivity to the cluster API server (control plane VIP)
  • SSH key used to create the Admin cluster should be available as a root, or you should have SUDO user access on all nodes in the target admin cluster.

See the GKE on Bare Metal quickstart for expanded step-by-step instructions for creating a hybrid cluster. Creating an admin cluster is similar to creating a hybrid cluster, except you don't run workloads on the admin cluster.

Logging into gcloud and creating a admin cluster config file

  1. Login to gcloud as a user using gcloud auth application-default login:
    2. gcloud auth application-default login
    You need to have a Project Owner/Editor role to use the automatic API enablement and Service Account creation features, described below. You can also add the following IAM roles to the user:
    • Service Account Admin
    • Service Account Key Admin
    • Project IAM Admin
    • Compute Viewer
    • Service Usage Admin
    Alternatively, if you already have a service account with those roles, run: 
    export GOOGLE_APPLICATION_CREDENTIALS=JSON_KEY_FILE
    JSON_KEY_FILE specifies the path to your service account JSON key file.
  2. Get your Cloud project id to use with cluster creation:
    3. export CLOUD_PROJECT_ID=$(gcloud config get-value project)

Creating an admin cluster config with bmctl

After you've logged into gcloud and have your project set up, you can create the cluster config file with the bmctl command. Note that in this example, all service accounts are automatically created by the bmctl create config command:

bmctl create config -c ADMIN_CLUSTER_NAME --enable-apis \
    --create-service-accounts --project-id=CLOUD_PROJECT_ID

The ADMIN_CLUSTER_NAME is the name of the cluster, and the CLOUD_PROJECT_ID is your project ID.

Here's an example to create a config file for a admin cluster called admin1 associated with project ID my-gcp-project: 

bmctl create config -c admin1 --create-service-accounts --enable-apis --project-id=my-gcp-project

The file is written to bmctl-workspace/admin1/admin1.yaml.

As an alternative to automatically enabling APIs and creating service accounts, you can also provide your existing service accounts with proper IAM permissions. This means you can skip the automatic service account creation in the previous step in the bmctl command:

bmctl create config -c admin1

Edit the cluster config file

Now that you have a cluster config file, edit it to make the following changes:

  1. Provide the SSH private key to access the admin cluster nodes:
    2. 
# bmctl configuration variables. Because this section is valid YAML but not a valid Kubernetes
# resource, this section can only be included when using bmctl to
# create the initial admin/admin cluster. Afterwards, when creating user clusters by directly
# applying the cluster and node pool resources to the existing cluster, you must remove this
# section.
gcrKeyPath:
/bmctl/bmctl-workspace/.sa-keys/my-gcp-project-anthos-baremetal-gcr.json
sshPrivateKeyPath: /path/to/your/ssh_private_key
gkeConnectAgentServiceAccountKeyPath: /bmctl/bmctl-workspace/.sa-keys/my-gcp-project-anthos-baremetal-connect.json
gkeConnectRegisterServiceAccountKeyPath: /bmctl/bmctl-workspace/.sa-keys/my-gcp-project-anthos-baremetal-register.json
cloudOperationsServiceAccountKeyPath: /bmctl/bmctl-workspace/.sa-keys/my-gcp-project-anthos-baremetal-cloud-ops.json
  2. Check to make sure the config specifies a cluster type of admin (the default value):
    3. 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: admin
  3. Change the configuration file to specify a multi-node, high availability, control plane. Specify an odd number of nodes to have a majority quorum for HA:
    4.   # Control plane configuration
  controlPlane:
    nodePoolSpec:
      nodes:
      # Control plane node pools. Typically, this is either a single machine
      # or 3 machines if using a high availability deployment.
      - address: 10.200.0.4
      - address: 10.200.0.5
      - address: 10.200.0.6

Create the admin cluster with the cluster config

Use the bmctl command to deploy the cluster: 

bmctl create cluster -c ADMIN_CLUSTER_NAME

ADMIN_CLUSTER_NAME specifies the cluster name created in the previous section.

The following shows an example of the command to create a cluster called admin1:

bmctl create cluster -c admin1

Sample complete admin cluster config

The following is a sample admin cluster config file created by the bmctl command. Note that in this sample config, placeholder cluster names, VIPs and addresses are used. They may not work for your network.


gcrKeyPath: /bmctl/bmctl-workspace/.sa-keys/my-gcp-project-anthos-baremetal-gcr.json
sshPrivateKeyPath: /bmctl/bmctl-workspace/.ssh/id_rsa
gkeConnectAgentServiceAccountKeyPath: /bmctl/bmctl-workspace/.sa-keys/my-gcp-project-anthos-baremetal-connect.json
gkeConnectRegisterServiceAccountKeyPath: /bmctl/bmctl-workspace/.sa-keys/my-gcp-project-anthos-baremetal-register.json
cloudOperationsServiceAccountKeyPath: /bmctl/bmctl-workspace/.sa-keys/my-gcp-project-anthos-baremetal-cloud-ops.json
---
apiVersion: v1
kind: Namespace
metadata:
  name: cluster-admin1
---
apiVersion: baremetal.cluster.gke.io/v1
kind: Cluster
metadata:
  name: admin1
  namespace: cluster-admin1
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: admin
  # Anthos cluster version.
  anthosBareMetalVersion: v1.6.2
  # GKE connect configuration
  gkeConnect:
    projectID: $GOOGLE_PROJECT_ID
  # Control plane configuration
  controlPlane:
    nodePoolSpec:
      nodes:
      # Control plane node pools. Typically, this is either a single machine
      # or 3 machines if using a high availability deployment.
      - address: 10.200.0.4
      - address: 10.200.0.5
      - address: 10.200.0.6
  # Cluster networking configuration
  clusterNetwork:
    # Pods specify the IP ranges from which Pod networks are allocated.
    pods:
      cidrBlocks:
      - 192.168.0.0/16
    # Services specify the network ranges from which service VIPs are allocated.
    # This can be any RFC 1918 range that does not conflict with any other IP range
    # in the cluster and node pool resources.
    services:
      cidrBlocks:
      - 10.96.0.0/12
  # Load balancer configuration
  loadBalancer:
    # Load balancer mode can be either 'bundled' or 'manual'.
    # In 'bundled' mode a load balancer will be installed on load balancer nodes during cluster creation.
    # In 'manual' mode the cluster relies on a manually-configured external load balancer.
    mode: bundled
    # Load balancer port configuration
    ports:
      # Specifies the port the LB serves the kubernetes control plane on.
      # In 'manual' mode the external load balancer must be listening on this port.
      controlPlaneLBPort: 443
    # There are two load balancer VIPs: one for the control plane and one for the L7 Ingress
    # service. The VIPs must be in the same subnet as the load balancer nodes.
    vips:
      # ControlPlaneVIP specifies the VIP to connect to the Kubernetes API server.
      # This address must not be in the address pools below.
      controlPlaneVIP: 10.200.0.71
      # IngressVIP specifies the VIP shared by all services for ingress traffic.
      # Allowed only in non-admin clusters.
      # This address must be in the address pools below.
      # ingressVIP: 10.0.0.2
    # AddressPools is a list of non-overlapping IP ranges for the data plane load balancer.
    # All addresses must be in the same subnet as the load balancer nodes.
    # Address pool configuration is only valid for 'bundled' LB mode in non-admin clusters.
    # addressPools:
    # - name: pool1
    #   addresses:
    #   # Each address must be either in the CIDR form (1.2.3.0/24)
    #   # or range form (1.2.3.1-1.2.3.5).
    #   - 10.0.0.1-10.0.0.4
    # A load balancer nodepool can be configured to specify nodes used for load balancing.
    # These nodes are part of the kubernetes cluster and run regular workloads as well as load balancers.
    # If the node pool config is absent then the control plane nodes are used.
    # Node pool configuration is only valid for 'bundled' LB mode.
    # nodePoolSpec:
    #  nodes:
    #  - address: <Machine 1 IP>
  # Proxy configuration
  # proxy:
  #   url: http://[username:password@]domain
  #   # A list of IPs, hostnames or domains that should not be proxied.
  #   noProxy:
  #   - 127.0.0.1
  #   - localhost
  # Logging and Monitoring
  clusterOperations:
    # Cloud project for logs and metrics.
    projectID: <Google Project ID>$GOOGLE_PROJECT_ID
    # Cloud location for logs and metrics.
    location: us-central1
    # Whether collection of application logs/metrics should be enabled (in addition to
    # collection of system logs/metrics which correspond to system components such as
    # Kubernetes control plane or cluster management agents).
    # enableApplication: false
  # Storage configuration
  storage:
    # lvpNodeMounts specifies the config for local PersistentVolumes backed by mounted disks.
    # These disks need to be formatted and mounted by the user, which can be done before or after
    # cluster creation.
    lvpNodeMounts:
      # path specifies the host machine path where mounted disks will be discovered and a local PV
      # will be created for each mount.
      path: /mnt/localpv-disk
      # storageClassName specifies the StorageClass that PVs will be created with. The StorageClass
      # is created during cluster creation.
      storageClassName: local-disks
    # lvpShare specifies the config for local PersistentVolumes backed by subdirectories in a shared filesystem.
    # These subdirectories are automatically created during cluster creation.
    lvpShare:
      # path specifies the host machine path where subdirectories will be created on each host. A local PV
      # will be created for each subdirectory.
      path: /mnt/localpv-share
      # storageClassName specifies the StorageClass that PVs will be created with. The StorageClass
      # is created during cluster creation.
      storageClassName: local-shared
      # numPVUnderSharedPath specifies the number of subdirectories to create under path.
      numPVUnderSharedPath: 5
  # Authentication; uncomment this section if you wish to enable authentication to the cluster with OpenID Connect.
  # authentication:
  #   oidc:
  #     # issuerURL specifies the URL of your OpenID provider, such as "https://accounts.google.com". The Kubernetes API
  #     # server uses this URL to discover public keys for verifying tokens. Must use HTTPS.
  #     issuerURL: <URL for OIDC Provider; required>
  #     # clientID specifies the ID for the client application that makes authentication requests to the OpenID
  #     # provider.
  #     clientID: <ID for OIDC client application; required>
  #     # clientSecret specifies the secret for the client application.
  #     clientSecret: <Secret for OIDC client application; optional>
  #     # kubectlRedirectURL specifies the redirect URL (required) for the gcloud CLI, such as
  #     # "http://localhost:[PORT]/callback".
  #     kubectlRedirectURL: <Redirect URL for the gcloud CLI; optional default is             "http://kubectl.redirect.invalid"
  #     # username specifies the JWT claim to use as the username. The default is "sub", which is expected to be a
  #     # unique identifier of the end user.
  #     username: <JWT claim to use as the username; optional, default is "sub">
  #     # usernamePrefix specifies the prefix prepended to username claims to prevent clashes with existing names.
  #     usernamePrefix: <Prefix prepended to username claims; optional>
  #     # group specifies the JWT claim that the provider will use to return your security groups.
  #     group: <JWT claim to use as the group name; optional>
  #     # groupPrefix specifies the prefix prepended to group claims to prevent clashes with existing names.
  #     groupPrefix: <Prefix prepended to group claims; optional>
  #     # scopes specifies additional scopes to send to the OpenID provider as a comma-delimited list.
  #     scopes: Additional scopes to send to OIDC provider as a comma-separated list; optional>
  #     # extraParams specifies additional key-value parameters to send to the OpenID provider as a comma-delimited
  #     # list.
  #     extraParams: Additional key-value parameters to send to OIDC provider as a comma-separated list; optional>
  #     # certificateAuthorityData specifies a Base64 PEM-encoded certificate authority certificate of your identity
  #     # provider. It's not needed if your identity provider's certificate was issued by a well-known public CA.
  #     certificateAuthorityData: Base64 PEM-encoded certificate authority certificate of your OIDC provider; optional>
  # Node access configuration; uncomment this section if you wish to use a non-root user
  # with passwordless sudo capability for machine login.
  # nodeAccess:
  #   loginUser: login user name