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5.2.12.2. Creating Red Hat Enterprise Linux CoreOS (RHCOS) machines by PXE or iPXE booting

Before you install a cluster on bare metal infrastructure that you provision, you must create RHCOS machines for it to use. You can use PXE or iPXE booting to create the machines.

Prerequisites

  • Obtain the Ignition config files for your cluster.
  • Familiarity configuring the necessary DHCP, TFTP, and HTTP services for providing PXE or iPXE infrastructure.
  • Have access to an HTTP server and TFTP server that you can access from your computer.

Procedure

  1. Upload the master, worker, and bootstrap Ignition config files that the installation program created to your HTTP server. Note the URLs of these files.

    重要

    If you plan to add more compute machines to your cluster after you finish installation, do not delete these files.

  2. Obtain the compressed metal RAW image, kernel and initramfs files from the Product Downloads page on the Red Hat customer portal or the RHCOS image mirror page.

    重要

    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. Only use RAW images for this procedure. RHCOS qcow2 images are not supported for bare metal installs.

    The file names contain the OpenShift Container Platform version number. They resemble the following examples:

    • Compressed metal RAW image: rhcos-<version>-<architecture>-metal.<architecture>.raw.gz
    • kernel: rhcos-<version>-<architecture>-installer-kernel-<architecture>
    • initramfs: rhcos-<version>-<architecture>-installer-initramfs.<architecture>.img
  3. Upload the RAW image to your HTTP server.

  4. Upload the additional files that are required for your booting method:

    • For traditional PXE, upload the kernel and initramfs files to your TFTP server.
    • For iPXE, upload the kernel and initramfs files to your HTTP server.
    重要

    If you plan to add more compute machines to your cluster after you finish installation, do not delete these files.

  5. Configure the network boot infrastructure so that the machines boot from their local disks after RHCOS is installed on them.

  6. Configure PXE or iPXE installation for the RHCOS images.

    Modify one of the following example menu entries for your environment and verify that the image and Ignition files are properly accessible:

    • For PXE: 

      DEFAULT pxeboot
TIMEOUT 20
PROMPT 0
LABEL pxeboot
    KERNEL rhcos-<version>-<architecture>-installer-kernel-<architecture> 1
    APPEND ip=dhcp rd.neednet=1 initrd=rhcos-<version>-<architecture>-installer-initramfs.<architecture>.img coreos.inst=yes coreos.inst.install_dev=sda coreos.inst.image_url=http://<HTTP_server>/rhcos-<version>-<architecture>-metal.<architecture>.raw.gz coreos.inst.ignition_url=http://<HTTP_server>/bootstrap.ign 2 3
      1
      Specify the location of the kernel file available on your TFTP server.
      2
      If you use multiple NICs, specify a single interface in the ip option. For example, to use DHCP on a NIC that is named eno1, set ip=eno1:dhcp.
      3
      Specify locations of the RHCOS files that you uploaded to your HTTP or TFTP server. The initrd parameter value is the location of the initramfs file on your TFTP server. The coreos.inst.image_url parameter value is the location of the compressed metal RAW image on your HTTP server, and the coreos.inst.ignition_url parameter value is the location of the bootstrap Ignition config file on your HTTP server.
      注記

      This configuration does not enable serial console access on machines with a graphical console. To configure a different console, add one or more console= arguments to the APPEND line. For example, add console=tty0 console=ttyS0 to set the first PC serial port as the primary console and the graphical console as a secondary console. For more information, see How does one set up a serial terminal and/or console in Red Hat Enterprise Linux?.

    • For iPXE: 

      kernel  http://<HTTP_server>/rhcos-<version>-<architecture>-installer-kernel-<architecture> ip=dhcp rd.neednet=1 initrd=rhcos-<version>-<architecture>-installer-initramfs.<architecture>.img coreos.inst=yes coreos.inst.install_dev=sda coreos.inst.image_url=http://<HTTP_server>/rhcos-<version>-<architecture>-metal.<architecture>.raw.gz coreos.inst.ignition_url=http://<HTTP_server>/bootstrap.ign 1 2
initrd http://<HTTP_server>/rhcos-<version>-<architecture>-installer-initramfs.<architecture>.img 3
boot
      1
      Specify locations of the RHCOS files that you uploaded to your HTTP server. The kernel parameter value is the location of the kernel file, the initrd parameter value references the name of the initramfs file that is supplied on the following initrd line, the coreos.inst.image_url parameter value is the location of the compressed metal RAW image, and the coreos.inst.ignition_url parameter value is the location of the bootstrap Ignition config file.
      2
      If you use multiple NICs, specify a single interface in the ip option. For example, to use DHCP on a NIC that is named eno1, set ip=eno1:dhcp.
      3
      Specify the location of the initramfs file that you uploaded to your HTTP server.
      注記

      This configuration does not enable serial console access on machines with a graphical console. To configure a different console, add one or more console= arguments to the kernel line. For example, add console=tty0 console=ttyS0 to set the first PC serial port as the primary console and the graphical console as a secondary console. For more information, see How does one set up a serial terminal and/or console in Red Hat Enterprise Linux?.

  7. If you use UEFI, perform the following actions:

    1. Provide the EFI binaries and grub.cfg file that are required for booting the system. You need the shim.efi binary and the grubx64.efi binary.

      • Extract the necessary EFI binaries by mounting the RHCOS ISO on your host and then mounting the images/efiboot.img file to your host. From the efiboot.img mount point, you then copy the EFI/redhat/shimx64.efi and EFI/redhat/grubx64.efi files to your TFTP server. 

        # mkdir -p /mnt/{iso,efiboot}
# mount -o loop rhcos-installer.x86_64.iso /mnt/iso
# mount -o loop,ro /mnt/iso/images/efiboot.img /mnt/efiboot
# cp /mnt/efiboot/EFI/redhat/{shimx64.efi,grubx64.efi} .
# umount /mnt/{efiboot,iso}
    2. Copy the EFI/redhat/grub.cfg file that is included in the RHCOS ISO to your TFTP server.

    3. Edit the grub.cfg file to include the following arguments: 

      menuentry 'Install Red Hat Enterprise Linux CoreOS' --class fedora --class gnu-linux --class gnu --class os {
	linux rhcos-<version>-<architecture>-installer-kernel-<architecture> nomodeset rd.neednet=1 coreos.inst=yes coreos.inst.install_dev=sda coreos.inst.image_url=http://<HTTP_server>/rhcos-<version>-<architecture>-metal.<architecture>.raw.gz coreos.inst.ignition_url=http://<HTTP_server>/bootstrap.ign 1
	initrd rhcos-<version>-<architecture>-installer-initramfs.<architecture>.img 2
}
      1
      The first argument to the linux line item is the location of the kernel file that you uploaded to your TFTP server. For the coreos.inst.image_url parameter value, specify the location of the compressed metal RAW image that you uploaded to your HTTP server. For the coreos.inst.ignition_url paramter, specify the location of the bootstrap Ignition config file that you uploaded to your HTTP server.
      2
      Specify the location of the initramfs file that you uploaded to your TFTP server.

  8. Continue to create the machines for your cluster.

    重要

    You must create the bootstrap and control plane machines at this time. If the control plane machines are not made schedulable, which is the default, also create at least two compute machines before you install the cluster.