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6.2.7. Creating Red Hat Enterprise Linux CoreOS (RHCOS) machines

Before you install a cluster on IBM Z infrastructure that you provision, you must install RHCOS on z/VM guest virtual machines for the cluster to use. Complete the following steps to create the machines.


  • An FTP server running on your provisioning machine that is accessible to the machines you create.


  1. Log in to Linux on your provisioning machine.
  2. Download the Red Hat Enterprise Linux CoreOS (RHCOS) installation files from the RHCOS image mirror.


    The RHCOS images might not change with every release of OpenShift Container Platform. You must download images with the highest version that is less than or equal to the OpenShift Container Platform version that you install. Use the image versions that match your OpenShift Container Platform version if they are available.

    Download the following files:

    • The initramfs: rhcos-<version>-installer-initramfs.img
    • The kernel: rhcos-<version>-installer-kernel
    • The operating system image for the disk on which you want to install RHCOS. This type can differ by virtual machine:

      rhcos-<version>-s390x-dasd.s390x.raw.gz for DASD

      rhcos-<version>-s390x-metal.s390x.raw.gz for FCP

  3. Create parameter files. The following parameters are specific for a particular virtual machine:

    • For coreos.inst.install_dev=, specify dasda for a DASD installation, or sda for FCP. Note that FCP requires zfcp.allow_lun_scan=0.
    • For rd.dasd=, specifys the DASD where RHCOS is to be installed.
    • rd.zfcp=<adapter>,<wwpn>,<lun> specifies the FCP disk to install RHCOS on.
    • For ip=, specify the following seven entries:

      1. The IP address for the machine.
      2. An empty string.
      3. The gateway.
      4. The netmask.
      5. The machine host and domain name in the form hostname.domainname. Omit this value to let RHCOS decide set it.
      6. The network interface name. Omit this value to let RHCOS decide set it.
      7. If you use static IP addresses, an empty string.
    • For coreos.inst.ignition_url=, specify the Ignition file for the machine role. Use bootstrap.ign, master.ign, or worker.ign.
    • All other parameters can stay as they are.

      Example parameter file, bootstrap-0.parm, for the bootstrap machine:

      rd.neednet=1 coreos.inst=yes coreos.inst.install_dev=dasda coreos.inst.image_url=ftp://
      ip= nameserver=
      rd.znet=qeth,0.0.bdf0,0.0.bdf1,0.0.bdf2,layer2=1,portno=0 zfcp.allow_lun_scan=0 cio_ignore=all,
      !condev rd.dasd=0.0.3490
  4. Transfer the initramfs, kernel, parameter files, and RHCOS images to z/VM, for example with FTP. For details about how to transfer the files with FTP and boot from the virtual reader, see Installing under Z/VM.
  5. Punch the files to the virtual reader of the z/VM guest virtual machine that is to become your bootstrap node.

    See PUNCH in the IBM Knowledge Center.


    You can use the CP PUNCH command or, if you use Linux, the vmur command to transfer files between two z/VM guest virtual machines.

  6. Log in to CMS on the bootstrap machine.
  7. IPL the bootstrap machine from the reader:

    $ ipl c

    See IPL in the IBM Knowledge Center.

  8. Repeat this procedure for the other machines in the cluster.