Boot modes for EKS Anywhere on Bare Metal

OS installation boot modes for EKS Anywhere on Bare Metal

In order to install an Operating System on a machine, the machine needs to boot into the EKS Anywhere Operating System Installation Environment (HookOS). This is accomplished in one of two ways. The first is via the network, also known as PXE boot. This is the default mode. The second is via a virtual CD/DVD device. In EKS Anywhere this is also known as ISO boot.

Network Boot

This is the default boot method used for machines in EKS Anywhere. This method requires the EKS Anywhere Bootstrap and Management Clusters to have layer 2 network access to the machines being booted. The network boot process hands out the initial bootloader location via DHCP. In EKS Anywhere this is the iPXE bootloader. The iPXE bootloader then downloads the EKS Anywhere OSIE image and boots into it. The following is a simplified sequence diagram of the network boot process:

network-boot

Cluster Spec Configuration - Network Boot

As this is the default method, no additional configuration is required. Follow the installation instructions as normal.

ISO Boot

This method does not require the EKS Anywhere Bootstrap and Management Clusters to have layer 2 network access to the machines being booted. It does not use DHCP or require layer 2 network access. Instead, the EKS Anywhere HookOS image is provided as a CD/DVD ISO file by the Tinkerbell stack. The HookOS ISO is then attached to the machine via the BMC as a virtual CD/DVD device. The machine is then booted into the virtual CD/DVD device and HookOS boots up. The following is a simplified sequence diagram of the ISO boot process:

iso-boot

Cluster Spec Configuration - ISO Boot

To enable the ISO boot method there is one required field and one optional field.

Required: TinkerbellDatacenterConfig.spec.isoBoot - Set this field to true to enable the ISO boot mode.
Optional: TinkerbellDatacenterConfig.spec.isoURL - This field is a string value that specifies the URL to the HookOS ISO file. If this field is not provided, the default HookOS ISO file will be used.

Important

In order to use the ISO boot mode all of the following must be true:

The BMC info for all machines must be provided in the hardware.csv file.
All BMCs must have virtual media mounting capabilities with remote HTTP(S) support.
All BMCs must have Redfish enabled and Redfish must have virtual media mounting capabilities.

spec:
  isoBoot: true
  hookIsoURL: "http://example.com/hookos.iso"

It is highly recommended that the HookOS ISO file is available locally in your environment and its location is specified in the hookIsoURL field. The default location for the HookOS ISO file is hosted in the cloud by AWS. This means that the Tinkerbell stack, and more specifically the Smee service, will need internet access to this location and Smee will need to pull from this location every time a machine is booted. This can lead to slow boot times and potential boot failures if the internet connection is slow, constrained, or lost.

Run the following commmand to download the HookOS ISO file:

BUNDLE_URL=$(eksctl anywhere version | grep "https://anywhere-assets.eks.amazonaws.com/releases/bundles" | tr -d ' ' | cut -d":" -f2,3)
IMAGE=$(curl -SsL $BUNDLE_URL | grep -E 'uri: .*hook-x86_64-efi-initrd.iso' | uniq | tr -d ' ' | cut -d":" -f2,3)
wget $IMAGE

Make this file available via a web server and put the full URL where this ISO is downloadable in the hookIsoURL field.