Installing a cluster on oVirt in a restricted network

The following items are required to install an OKD cluster on a oVirt environment.

In OKD 4.8, you can perform an installation that does not require an active connection to the internet to obtain software components. Restricted network installations can be completed using installer-provisioned infrastructure or user-provisioned infrastructure, depending on the cloud platform to which you are installing the cluster.

If you choose to perform a restricted network installation on a cloud platform, you still require access to its cloud APIs. Some cloud functions, like Amazon Web Service’s Route 53 DNS and IAM services, require internet access. Depending on your network, you might require less internet access for an installation on bare metal hardware or on VMware vSphere.

To complete a restricted network installation, you must create a registry that mirrors the contents of the OKD registry and contains the installation media. You can create this registry on a mirror host, which can access both the internet and your closed network, or by using other methods that meet your restrictions.

To install and run an OKD version 4.8 cluster, the oVirt environment must meet the following requirements.

Not meeting these requirements can cause the installation or process to fail. Additionally, not meeting these requirements can cause the OKD cluster to fail days or weeks after installation.

The following requirements for CPU, memory, and storage resources are based on default values multiplied by the default number of virtual machines the installation program creates. These resources must be available in addition to what the oVirt environment uses for non-OKD operations.

By default, the installation program creates seven virtual machines during the installation process. First, it creates a bootstrap virtual machine to provide temporary services and a control plane while it creates the rest of the OKD cluster. When the installation program finishes creating the cluster, deleting the bootstrap machine frees up its resources.

If you increase the number of virtual machines in the oVirt environment, you must increase the resources accordingly.

Verify that the oVirt environment meets the requirements to install and run an OKD cluster. Not meeting these requirements can cause failures.

All the Fedora CoreOS (FCOS) machines require networking to be configured in initramfs during boot to fetch their Ignition config files.

During the initial boot, the machines require an IP address configuration that is set either through a DHCP server or statically by providing the required boot options. After a network connection is established, the machines download their Ignition config files from an HTTP or HTTPS server. The Ignition config files are then used to set the exact state of each machine. The Machine Config Operator completes more changes to the machines, such as the application of new certificates or keys, after installation.

It is recommended to use a DHCP server for long-term management of the cluster machines. Ensure that the DHCP server is configured to provide persistent IP addresses, DNS server information, and hostnames to the cluster machines.

The Kubernetes API server must be able to resolve the node names of the cluster machines. If the API servers and worker nodes are in different zones, you can configure a default DNS search zone to allow the API server to resolve the node names. Another supported approach is to always refer to hosts by their fully-qualified domain names in both the node objects and all DNS requests.

Configure your firewall so your cluster has access to required sites.

See also:

Configure infrastructure-provided DNS to allow the correct resolution of the main components and services. If you use only one load balancer, these DNS records can point to the same IP address.

In OKD deployments, DNS name resolution is required for the following components:

Reverse DNS resolution is also required for the Kubernetes API, the bootstrap machine, the control plane machines, and the compute machines.

DNS A/AAAA or CNAME records are used for name resolution and PTR records are used for reverse name resolution. The reverse records are important because Fedora CoreOS (FCOS) uses the reverse records to set the hostnames for all the nodes, unless the hostnames are provided by DHCP. Additionally, the reverse records are used to generate the certificate signing requests (CSR) that OKD needs to operate.

The following DNS records are required for a user-provisioned OKD cluster and they must be in place before installation. In each record, <cluster_name> is the cluster name and <base_domain> is the base domain that you specify in the install-config.yaml file. A complete DNS record takes the form: <component>.<cluster_name>.<base_domain>..

To run the binary openshift-install installation program and Ansible scripts, set up the oVirt Engine or an Fedora computer with network access to the oVirt environment and the REST API on the Engine.

Download the CA certificate from the oVirt Manager and set it up on the installation machine.

You can download the certificate from a webpage on the oVirt Engine or by using a curl command.

Later, you provide the certificate to the installation program.

During an OKD installation, you can provide an SSH public key to the installation program. The key is passed to the Fedora CoreOS (FCOS) nodes through their Ignition config files and is used to authenticate SSH access to the nodes. The key is added to the ~/.ssh/authorized_keys list for the core user on each node, which enables password-less authentication.

After the key is passed to the nodes, you can use the key pair to SSH in to the FCOS nodes as the user core. To access the nodes through SSH, the private key identity must be managed by SSH for your local user.

If you want to SSH in to your cluster nodes to perform installation debugging or disaster recovery, you must provide the SSH public key during the installation process. The ./openshift-install gather command also requires the SSH public key to be in place on the cluster nodes.

Download the Ansible playbooks for installing OKD version 4.8 on oVirt.

You use the inventory.yml file to define and create elements of the OKD cluster you are installing. This includes elements such as the Fedora CoreOS (FCOS) image, virtual machine templates, bootstrap machine, control plane nodes, and worker nodes. You also use inventory.yml to destroy the cluster.

The following inventory.yml example shows you the parameters and their default values. The quantities and numbers in these default values meet the requirements for running a production OKD cluster in a oVirt environment.

This section consists of two profiles:

These profiles have the following parameters. The default values of the parameters meet the minimum requirements for running a production cluster. You can increase or customize these values to meet your workload requirements.

This final section, vms, defines the virtual machines you plan to create and deploy in the cluster. By default, it provides the minimum number of control plane and worker nodes for a production environment.

vms contains three required elements:

For virtual machines, metadata.infraID prepends the name of the virtual machine with the infrastructure ID from the metadata.json file you create when you build the Ignition files.

The playbooks use the following code to read infraID from the specific file located in the ocp.assets_dir.

Update the Fedora CoreOS (FCOS) image settings of the inventory.yml file. Later, when you run this file one of the playbooks, it downloads a compressed Fedora CoreOS (FCOS) image from the image_url URL to the local_cmp_image_path directory. The playbook then uncompresses the image to the local_image_path directory and uses it to create oVirt/oVirt templates.

You create an installation configuration file by running the installation program, openshift-install, and responding to its prompts with information you specified or gathered earlier.

When you finish responding to the prompts, the installation program creates an initial version of the install-config.yaml file in the assets directory you specified earlier, for example, ./wrk/install-config.yaml

The installation program also creates a file, $HOME/.ovirt/ovirt-config.yaml, that contains all the connection parameters that are required to reach the Engine and use its REST API.

NOTE: The installation process does not use values you supply for some parameters, such as Internal API virtual IP and Ingress virtual IP, because you have already configured them in your infrastructure DNS.

It also uses the values you supply for parameters in inventory.yml, like the ones for oVirt cluster, oVirt storage, and oVirt network. And uses a script to remove or replace these same values from install-config.yaml with the previously mentioned virtual IPs.

Together, the values you enter for the oVirt cluster and Base Domain prompts form the FQDN portion of URLs for the REST API and any applications you create, such as https://api.ocp4.example.org:6443/ and https://console-openshift-console.apps.ocp4.example.org.

You can get the pull secret from the Red Hat OpenShift Cluster Manager.

You can customize the install-config.yaml file to specify more details about your OKD cluster’s platform or modify the values of the required parameters.

Here, you use three Python scripts to override some of the installation program’s default behaviors:

Use the installation program to generate a set of manifest files in the assets directory.

The command to generate the manifest files displays a warning message before it consumes the install-config.yaml file.

If you plan to reuse the install-config.yaml file, create a backup copy of it before you back it up before you generate the manifest files.

Because you are manually creating and deploying the control plane machines, you must configure a manifest file to make the control plane nodes non-schedulable.

To build the Ignition files from the manifest files you just generated and modified, you run the installation program. This action creates a Fedora CoreOS (FCOS) machine, initramfs, which fetches the Ignition files and performs the configurations needed to create a node.

In addition to the Ignition files, the installation program generates the following:

The Ansible playbooks for this installation process use the value of infraID as a prefix for the virtual machines they create. This prevents naming conflicts when there are multiple installations in the same oVirt/oVirt cluster.

After confirming the variables in the inventory.yml, you run the first Ansible provisioning playbook, create-templates-and-vms.yml.

This playbook uses the connection parameters for the oVirt Engine from $HOME/.ovirt/ovirt-config.yaml and reads metadata.json in the assets directory.

If a local Fedora CoreOS (FCOS) image is not already present, the playbook downloads one from the URL you specified for image_url in inventory.yml. It extracts the image and uploads it to oVirt to create templates.

The playbook creates a template based on the control_plane and compute profiles in the inventory.yml file. If these profiles have different names, it creates two templates.

When the playbook finishes, the virtual machines it creates are stopped. You can get information from them to help configure other infrastructure elements. For example, you can get the virtual machines' MAC addresses to configure DHCP to assign permanent IP addresses to the virtual machines.

You create a bootstrap machine by running the bootstrap.yml playbook. This playbook starts the bootstrap virtual machine, and passes it the bootstrap.ign Ignition file from the assets directory. The bootstrap node configures itself so it can serve Ignition files to the control plane nodes.

To monitor the bootstrap process, you use the console in the oVirt Administration Portal or connect to the virtual machine by using SSH.

You create the control plane nodes by running the masters.yml playbook. This playbook passes the master.ign Ignition file to each of the virtual machines. The Ignition file contains a directive for the control plane node to get the Ignition from a URL such as https://api-int.ocp4.example.org:22623/config/master. The port number in this URL is managed by the load balancer, and is accessible only inside the cluster.

You can verify your OKD cluster’s status during or after installation.

After the wait-for command shows that the bootstrap process is complete, you must remove the bootstrap virtual machine to free up compute, memory, and storage resources. Also, remove settings for the bootstrap machine from the load balancer directives.

Creating worker nodes is similar to creating control plane nodes. However, worker nodes workers do not automatically join the cluster. To add them to the cluster, you review and approve the workers' pending CSRs (Certificate Signing Requests).

After approving the first requests, you continue approving CSR until all of the worker nodes are approved. When you complete this process, the worker nodes become Ready and can have pods scheduled to run on them.

Finally, monitor the command line to see when the installation process completes.

Operator catalogs that source content provided by Red Hat and community projects are configured for OperatorHub by default during an OKD installation. In a restricted network environment, you must disable the default catalogs as a cluster administrator.