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Install: z/VM User Provided Infrastructure

The steps for performing a UPI-based install are outlined here. Several Ansible Playbooks are provided as an example to help model your own.

Table of contents

  1. Minimum compute requirements

  2. Network topology requirements

  3. DNS requirements

  4. Getting Ignition configs for machines

  5. Getting OS related assets for machines

  6. Booting machines with RHCOS and Ignition configs

  7. Watching your installation (bootstrap complete, cluster available)

  8. Example Bare-Metal UPI deployment

Compute

The smallest OpenShift 4.x clusters require the following host:

  • 1 bootstrap machine.

  • 3 control plane machines.

  • at least 2 worker machines.

NOTE: The cluster requires the bootstrap machine to deploy the OpenShift cluster on to the 3 control plane machines, and you can remove the bootstrap machine.

The bootstrap and control plane machines must use Red Hat Enterprise Linux CoreOS (RHCOS) as the operating system.

Minimum resource requirements

Processing Memory Storage Networking

[todo-link-to-minimum-resource-requirements]

Network Topology Requirements

OpenShift 4.x on Z currently requires all nodes to have internet access to pull images for platform containers and provide telemetry data to Red Hat. OpenShift generally supports air-gapped installs, but this feature is not yet available for z/VM.

Load balancers

Before you install OpenShift, you must provision two load balancers.

  • A load balancer for the control plane and bootstrap machines that targets port 6443 (Kubernetes APIServer) and 22623(Machine Config server). Port 6443 must be accessible to both clients external to the cluster and nodes within the cluster, and port 22623 must be accessible to nodes within the cluster.

    NOTE: Bootstrap machine can be deleted as target after cluster installation is finished.

  • A load balancer for the machines that run the ingress router pods that balances ports 443 and 80. Both the ports must be accessible to both clients external to the cluster and nodes within the cluster.

    NOTE: A working configuration for the ingress router is required for an OpenShift 4.x cluster.

    NOTE: The default configuration for Cluster Ingress Operator deploys the ingress router to worker nodes in the cluster. The administrator needs to configure the ingress after the control plane has been bootstrapped.

Connectivity between machines

You must configure the network connectivity between machines to allow cluster components to communicate.

  • etcd

    As the etcd members are located on the control plane machines. Each control plane machine requires connectivity to etcd server, etcd peer and etcd-metrics on every other control plane machine.

  • OpenShift SDN

    All the machines require connectivity to certain reserved ports on every other machine to establish in-cluster networking. For more details refer doc.

  • Kubernetes NodePort

    All the machines require connectivity to Kubernetes NodePort range 30000-32767 on every other machine for OpenShift platform components.

  • OpenShift reserved

    All the machines require connectivity to reserved port ranges 10250-12252 and 9000-9999 on every other machine for OpenShift platform components.

DNS requirements

  • Kubernetes API

    OpenShift 4.x requires the DNS records api.$cluster_name.$base_domain and api-int.$cluster_name.$base_domain to point to the Load balancer targeting the control plane machines. Both records must be resolvable from all the nodes within the cluster. The api.$cluster_name.$base_domain must also be resolvable by clients external to the cluster.

  • etcd

    For each control plane machine, OpenShift 4.x requires DNS records etcd-$idx.$cluster_name.$base_domain to point to $idx'th control plane machine. The DNS record must resolve to an unicast IPV4 address for the control plane machine and the records must be resolvable from all the nodes in the cluster.

    For each control plane machine, OpenShift 4.x also requires a SRV DNS record for etcd server on that machine with priority 0, weight 10 and port 2380. For 3 control plane cluster, the records look like:

    # _service._proto.name.                            TTL   class SRV priority weight port target.
_etcd-server-ssl._tcp.$cluster_name.$base_domain   86400 IN    SRV 0        10     2380 etcd-0.$cluster_name.$base_domain.
_etcd-server-ssl._tcp.$cluster_name.$base_domain   86400 IN    SRV 0        10     2380 etcd-1.$cluster_name.$base_domain.
_etcd-server-ssl._tcp.$cluster_name.$base_domain   86400 IN    SRV 0        10     2380 etcd-2.$cluster_name.$base_domain.

  • OpenShift Routes

    OpenShift 4.x requires the DNS record *.apps.$cluster_name.$base_domain to point to the Load balancer targeting the machines running the ingress router pods. This record must be resolvable by both clients external to the cluster and from all the nodes within the cluster.

Getting Ignition configs for machines

The OpenShift Installer provides administrators various assets that are required to create an OpenShift cluster, namely:

  • Ignition configs: The OpenShift Installer provides Ignition configs that should be used to configure the RHCOS based bootstrap and control plane machines using bootstrap.ign and master.ign respectively. The OpenShift Installer also provides worker.ign that can be used to configure the RHCOS based worker machines, but also can be used as source for configuring RHEL based machines [todo-link-to-BYO-RHEL].

  • Admin Kubeconfig: The OpenShift Installer provides a kubeconfig with admin level privileges to Kubernetes APIServer.

    NOTE: This kubeconfig is configured to use api.$cluster_name.$base_domain DNS name to communicate with the Kubernetes APIServer.

Setting up install-config for installer

The OpenShift installer uses an Install Config to drive all install time configuration.

An example install config for bare-metal UPI is as follows:

apiVersion: v1
## The base domain of the cluster. All DNS records will be sub-domains of this base and will also include the cluster name.
baseDomain: example.com
compute:
- name: worker
  replicas: 3
controlPlane:
  name: master
  replicas: 2
metadata:
  ## The name for the cluster
  name: test
platform:
  none: {}
## The pull secret that provides components in the cluster access to images for OpenShift components.
pullSecret: ''
## The default SSH key that will be programmed for `core` user.
sshKey: ''

Create a directory that will be used by the OpenShift installer to provide all the assets. For example test-bare-metal,

$ mkdir test-bare-metal
$ tree test-bare-metal
test-bare-metal

0 directories, 0 files

Copy your install-config to the INSTALL_DIR. For example using the test-bare-metal as our INSTALL_DIR,

$ cp <your-instal-config> test-bare-metal/install-config.yaml
$ tree test-bare-metal
test-bare-metal
└── install-config.yaml

0 directories, 1 file

NOTE: The filename for install-config in the INSTALL_DIR must be install-config.yaml

Invoking the installer to get Ignition configs

Given that you have setup the INSTALL_DIR with the appropriate install-config, you can create the Ignition configs by using the create ignition-configs target. For example,

$ openshift-install --dir test-bare-metal create ignition-configs
INFO Consuming "Install Config" from target directory
$ tree test-bare-metal
test-bare-metal
├── auth
│   └── kubeconfig
├── bootstrap.ign
├── master.ign
└── worker.ign

1 directory, 4 files

The bootstrap.ign, master.ign, and worker.ign files must be made available as http/https file downloads resolvable by the RHCOS nodes.

Booting machines with RHCOS and Ignition configs

Required kernel parameters for IPL boot

A kernel parameter file must be created for each node with the following parameters:

  • rd.neednet=1: CoreOS Installer needs internet access to fetch the OS image that needs to be installed on the machine.

  • IP configuration arguments may be required to access the network.

  • CoreOS Installer arguments are required to be configured to install RHCOS and setup the Ignition config file for that machine.

  • console=ttysclp0 : Console TTY argument for s390x

  • rd.znet, rd.dasd, and/or rd.zfcp : IBM Z device ID arguments are required to access network and disk devices.

IPL Boot RHCOS on z/VM

  • Using a 3270 console, connect to each guest and clear the z/VM virtual reader
logon <zvm_user> here
cp query rdr all
cp pur rdr all
  • For each z/VM guest, punch the RHCOS kernel, parameters file, and initramfs into the guest's virtual reader
    • example using vmur from another guest on the same z/VM hypervisor
# obtain the RHCOS images
$ curl -O <RHCOS kernel>
$ curl -O <RHCOS initramfs>

# load the virtual punch card devices
$ cio_ignore -r c-e
# activate the virtual punch card devices
$ chccwdev -e c-e

# punch the kernel into the virtual reader
$ vmur pun -r -u <z/vm guest id> -N kernel.img rhcos-<version>-installer-kernel
# punch the parameter file created in an earlier step
$ vmur pun -r -u <z/vm guest id> -N generic.parm <bootstrap,master,worker>.prm
# punch the initramfs into the virtual reader
$ vmur pun -r -u <z/vm guest id> -N initrd.img rhcos-<version>-installer-initramfs.img
  • Using a 3270 console, connect to each guest and boot from the virtual reader
cp ipl 00c
cp set run on

Watching your installation

Monitor for bootstrap-complete

The administrators can use the wait-for bootstrap-complete target of the OpenShift Installer to monitor cluster bootstrapping. The command succeeds when it notices bootstrap-complete event from Kubernetes APIServer. This event is generated by the bootstrap machine after the Kubernetes APIServer has been bootstrapped on the control plane machines. For example,

$ openshift-install --dir test-bare-metal wait-for bootstrap-complete
INFO Waiting up to 30m0s for the Kubernetes API at https://api.test.example.com:6443...
INFO API v1.12.4+c53f462 up
INFO Waiting up to 30m0s for the bootstrap-complete event...

Configure Image Registry Storage Provisioner

The Cluster Image Registry Operator does not pick an storage backend for None platform. Therefore, the cluster operator will be stuck in progressing because it is waiting for the administrator to configure a storage backend for the image-registry. NFS should be picked as a storage-backend.

Configuring NFS

NFS is currently the only supported persistent storage option for OpenShift on Z. To make an existing NFS share accessible for OpenShift to use as persistent storage, users must first attach it as a Persistent Volume. At least 100GB of NFS storage space must be available for the image registry claim.

apiVersion: v1
kind: PersistentVolume
spec:
  accessModes:
  - ReadWriteMany
  - ReadWriteOnce
  capacity:
    storage: 100Gi
  nfs:
    path: <NFS export path>
    server: <ip of NFS server>
  persistentVolumeReclaimPolicy: Recycle
  volumeMode: Filesystem
status: {}

Once the persistent volume is created, the image registry must be patched to use it.

oc patch configs.imageregistry.operator.openshift.io/cluster --type merge --patch '{"spec":{"storage":{"pvc":{"claim":""}}}}'

Configuring Local Storage (testing/development only)

Alternatively, for non-production clusters, emptyDir can be used for testing instead of NFS.

oc patch configs.imageregistry.operator.openshift.io cluster --type merge --patch '{"spec":{"storage":{"emptyDir":{}}}}'

Disabling Control Plane Schedulability

By default, when the OpenShift installer creates a cluster without any managed workers (as is the default in a UPI installation), it configures the scheduler to allow user-created application pods to be scheduled to the master nodes. In a production cluster, the master nodes should not be schedulable so that user-created applications can not consume resources dedicated to the control plane. Users should configure the cluster to disable master schedulability.

oc patch schedulers.config.openshift.io/cluster --type merge --patch '{"spec":{"mastersSchedulable": false}}'

Monitor for cluster completion

The administrators can use the wait-for install-complete target of the OpenShift Installer to monitor cluster completion. The command succeeds when it notices that Cluster Version Operator has completed rolling out the OpenShift cluster from Kubernetes APIServer.

$ openshift-install wait-for install-complete
INFO Waiting up to 30m0s for the cluster to initialize...

Example z/VM UPI configuration

An example ansible configuration for deploying a self-contained, development/testing cluster on z/VM is available. This example configuration demonstrates a minimal set of infrastructure services to bring up a running cluster. It is not a production-ready configuration.

The repository includes examples of the following user-provided components, which are intended to serve as a guide for designing a user's cluster topology.

  • DNS
  • Load Balancing
  • DHCP
  • File Server (for Ignition configs)