How to use network-kargs to deploy RHCOS Nodes with Static IPs in Openshift 4 on VMware

Resolution

Starting in OpenShift Container Platform 4.6, Red Hat CoreOS Enterprise Linux has the ability to utilize a static network configuration and override the automatic DHCP setup. Custom networking command-line ip= parameter can be configured via guestinfo.afterburn.initrd.network-kargs property.

Note: guestinfo.afterburn.initrd.network-kargs property must be set on the VM before the first boot and it does not affect subsequent boots.

The full syntax of the ip= parameter is documented in Dracut manpages.

ip=<client-IP>:[<peer>]:<gateway-IP>:<netmask>:<client_hostname>:<interface>:{none|off|dhcp|on|any|dhcp6|auto6|ibft}[:[<dns1>][:<dns2>]]
           explicit network configuration. If you want do define a IPv6
           address, put it in brackets (e.g. [2001:DB8::1]). This
           parameter can be specified multiple times.  <peer> is
           optional and is the address of the remote endpoint for
           pointopoint interfaces and it may be followed by a slash and
           a decimal number, encoding the network prefix length.

Utilizing the govc vSphere CLI you can use the following example to deploy a new node called Worker3 from the RHCOS46 Template to the raid0 Datastore with 4 vCPU, 16GB of RAM, on the 10.0.0.x-254 Network to the openshift-ctxdz folder.

WORKER_CONFIG=$(cat worker.ign | base64 -w0)
IPCFG="ip=10.0.0.103::10.0.0.254:255.255.255.0:worker3:ens192:off:10.0.0.1:10.0.0.2"
govc vm.clone -vm=RHCOS46 -ds=raid0 -c=4 -m=16384 -net=10.0.0.x-24 -folder=openshift-ctxdz -on=false worker3
govc vm.disk.change -vm worker3 -size 120G
govc vm.change -vm worker3 -e "guestinfo.ignition.config.data.encoding=base64"
govc vm.change -vm worker3 -e "guestinfo.ignition.config.data=${WORKER_CONFIG}"
govc vm.change -vm worker3 -e "guestinfo.afterburn.initrd.network-kargs=${IPCFG}"
govc vm.power -on worker3

In this example, using the Ansible along with the vmware_guest module, you will be deploying the same node Worker3 from the RHCOS46 Template to the raid0 Datastore with 4 vCPU, 16GB of RAM, on the 10.0.0.x-254 Network to the openshift-ctxdz folder.

NOTE - You will need to define the workerContent as a variable with the contents of worker.ign.

  - name: Create worker VMs from the template
    vmware_guest:
      hostname: vcenter.lab.int
      username: Administrator@vsphere.local
      password: ...
      datacenter: OCP4
      validate_certs: no
      folder: /vm/openshift-ctxdz/
      name: worker3
      state: PoweredOn
      template: RHCOS46
      disk:
      - size_gb: 120
        type: thin
        datastore: raid0
      hardware:
        memory_mb: 16384
        num_cpus: 4
        memory_reservation_lock: True
      networks:
      - name: 10.0.0.x-254
      wait_for_ip_address: no
      customvalues:
       - key: guestinfo.ignition.config.data
         value: "{{ workerContent }}"
       - key: guestinfo.ignition.config.data.encoding
         value: base64
       - key: guestinfo.afterburn.initrd.network-kargs
         value: "ip=10.0.0.103::10.0.0.254:255.255.255.0:worker3:ens192:off:10.0.0.1:10.0.0.2"

If you no longer have access to your Master or Worker Ignition files you can retrieve them by following KCS: How to retrieve Master or Worker Ignition Configuration?

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