Set up High Availability (HA) Kubernetes on the service cluster

With Omnia, you can deploy a service Kubernetes cluster on the designated service nodes to efficiently distribute workload and manage resources for telemetry data collection. This setup reduces the processing load on the OIM node and enhances overall scalability. Each service_kube_node is responsible for collecting telemetry data from its assigned subset of compute nodes. Federated way of telemetry data collection improves efficiency for large-scale clusters.

Prerequisites

• To deploy Kubernetes on service cluster, ensure that service_k8s is added under softwares in the /opt/omnia/input/project_default/software_config.json. Refer the sample config file below:

  {
  
       "cluster_os_type": "rhel",
        "cluster_os_version": "10.0",
         "repo_config": "always",
         "softwares": [
              {"name": "default_packages", "arch": ["x86_64","aarch64"]}
              {"name": "nfs", "arch": ["x86_64","aarch64"]},
              {"name": "service_k8s","version": "1.31.4", "arch": ["x86_64"]}
          ],
  
       "service_k8s": [
              {"name": "service_kube_control_plane"},
              {"name": "service_etcd"},
              {"name": "service_kube_node"}
      ]
  
  }
  

• Omnia supports only Kubernetes version 1.31.4.

• If you want to install CSI PowerScale driver, ensure that you provide the required values. Click Deploy CSI drivers for Dell PowerScale storage solutions for more information.

• Ensure that there are a minimum of three kube_control_planes.

• Ensure that the kube_control_planes has a full-featured RHEL operating system (OS) installed.

• Ensure that a hostname is configured on all the kube_control_planes.

• The kube_control_planes has internet access to download necessary packages for cluster deployment and configuration.

• Ensure that the nfs server is reachable on all the diskless and diskfull nodes.

• The kube_control_planes must be equipped with two active Network Interface Cards (NICs):

  • One connected to the public network. It is used for accessing the internet.

  • One dedicated to internal cluster communication. It is used for internal cluster communication, Kubernetes deployment activities, and for accessing the Pulp repositories hosted on the OIM. The Admin interface must be assigned an IP address from the admin network range and must be reachable from the OIM.

• To use NFS for service Kubernetes cluster, ensure the following prerequisites are met:

  • The NFS share has 755 permissions and no_root_squash is enabled on the mounted NFS share.

  • Edit the /etc/exports file on the NFS server to include the no_root_squash option for the server_share_path.

    /<your_server_share_path>  *(rw,sync,no_root_squash,no_subtree_check)
    

• Ensure that the following kube_control_planes hostname prerequisites are met. See Prerequisites.

Steps

1. Run local_repo.yml playbook to download the artifacts required to set up Kubernetes on the service cluster nodes.

2. Fill in the service cluster details in the functional_groups_config.yml: Create groups and assign functional roles to the nodes.

3. Fill the omnia_config.yml, high_availability_config.yml (for service cluster HA), and storage_config.yml. The nfs_name mentioned in storage_config.yml should match the nfs_storage_name of the entries for the service_k8s_cluster in omnia_config.yml where deployment is set to true. See Input parameters for the cluster. See the following sample. The NFS share is utilized by the Kubernetes cluster to mount necessary resources.

   nfs_client_params:
   -{
      nfs_name: "nfs_storage_default"
      server_ip: "", # Provide the IP of the NFS server
      server_share_path: "", # Provide server share path of the NFS Server
      client_share_path: /opt/omnia,,
      client_mount_options: "nosuid,rw,sync,hard,intr",
      nfs_name: nfs_k8s
   }
   

4. Run ansible-playbook utils/connect_external_server.yml -i <inv>.

   This playbook is used to set up passwordless SSH to the kube_control_planes and updating the repositories and plup repository certificates. The Ansible inventory must be created using the Admin network IPs of the control plane nodes because these IPs are used for Kubernetes deployment. See the following sample:

   Sample for inv:

   [kube_control_plane]
   10.5.0.211  ansible_user=root ansible_ssh_pass=****
   10.5.0.212  ansible_user=root ansible_ssh_pass=****
   10.5.0.213  ansible_user=root ansible_ssh_pass=****
   

5. Run ansible-playbook service_k8s_cluster.yml -i <inv>.

   This playbook deploys the service_k8s cluster with diskfull kube controller nodes and also extracts the configuration required for diskless kube nodes. It generates the kubeadm token and cloud-init vars for diskless kube node. The token expires after 24 hours. The step 5 and step 6 need to be executed within 24 hours and pxe boot also needs to be completed. If the token gets expired , use the script ansible-playbook scheduler/generate_token_and_pod_status.yml -i <inv>  --tags kubeadm_token to generate the new token and run discovery.yml again and pxe boot the nodes.

Once all the required input files are filled up, use the below commands to set up Kubernetes on the service cluster:

ssh omnia_core
ansible-playbook omnia.yml - i <inv>

OR,

cd /omnia/scheduler
ansible-playbook service_k8s_cluster.yml - i <inv>


Sample for inv:


    [kube_control_plane]
    10.5.0.211
    10.5.0.212
    10.5.0.213
    [etcd]
    10.5.0.211
    10.5.0.212
    10.5.0.213

6. Run build.image.yml playbook to build diskless images for cluster nodes. See Build cluster node images.

7. Run discovery.yml playbook to discover the potential cluster nodes, configure the boot script, and cloud-init based on the functional groups. See Discover cluster nodes

   After successfully running the discovery.yml playbook, you can either manually PXE boot the nodes or use the set_pxe_boot.yml playbook. PXE booting allows the nodes to load diskless images from the Omnia Infrastructure Manager (OIM). For detailed steps on using set_pxe_boot.yml, see Set PXE Boot Order.

8. After all the diskless nodes are pxebooted, use the utility to check the status of service cluster nodes and pods: ansible-playbook scheduler/generate_token_and_pod_status.yml -i <inv>  --tags pod_status

Additional installations

After deploying Kubernetes, the following additional packages are installed on top of the Kubernetes stack on the service cluster:

1. nfs-client-provisioner

   • NFS subdir external provisioner is an automatic provisioner that use your existing and already configured external NFS server to support dynamic provisioning of Kubernetes Persistent Volumes via Persistent Volume Claims (PVC).

   • The nfs_name mentioned in storage_config.yml should match the nfs_storage_name of the entries for the service_k8s_cluster.

   • The path to PVC is mentioned under {{ nfs_server_share_path }}.

   Click here for more information.

Accessing Kubernetes Dashboard Using LoadBalancer and Token Authentication

1. Edit the Dashboard Service to Use LoadBalancer.

   kubectl edit svc kubernetes-dashboard -n kube-system
   

In the editor, modify type: ClusterIP to type: LoadBalancer and save.

2. Check for the External LoadBalancer IP.

   kubectl get svc kubernetes-dashboard -n kube-system
   

3. Create admin service account and role binding.

   kubectl create serviceaccount dashboard-admin-sa -n kube-system
   kubectl create clusterrolebinding dashboard-admin-sa \
      --clusterrole=cluster-admin \
      --serviceaccount=kube-system:dashboard-admin-sa
   

4. Generate the Admin Login Token.

   kubectl -n kube-system create token dashboard-admin-sa
   

Copy the resulting token string.

5. Access the Kubernetes Dashboard. In your web browser, go to <https://<EXTERNAL-IP>/> select Token authentication, and paste your token to log in.

Next step

To know how to deploy the iDRAC telemetry containers on the service cluster, click here.

If you have any feedback about Omnia documentation, please reach out at omnia.readme@dell.com.