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I am setting up a cluster that is meant to run CentOS 8 on each node. I know that I have to define the xcat osimage that will be deployed to each node. The xcat osimage is created from the CentOS iso file. Yet, I do not know which image to choose: DVD image will be bloated for my cluster, but boot image will not install until a mirror and a group of rpms are selected to install (this is based on what I see when installing these images on VirtualBox)

Is there a way to select the RPMs that I want to install from the DVD iso from xcat ? Do I have to create my own iso? If so, how?

Alejandro Arcila
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On xCAT you must always import the full DVD image. This does not means that you'll add everything to the compute nodes. xCAT only preloads the content so it can relies on those files to deploy your compute nodes.

You decide what will be installed or not on each image. It will depend if you run your cluster with centos8-x86_64-install-compute or centos8-x86_64-netboot-compute. The first one is stateful where everything is installed on the disk of the compute node while the last one is stateless, where the compute node will always boot from network to fetch it's image and run it from RAM.

Customization is done on /install directory and changing what you want to on osimage definitions.

On the xCAT manual you can read how to add packages to the installation, as stated here: https://xcat-docs.readthedocs.io/en/stable/guides/admin-guides/manage_clusters/common/deployment/additionalpkg/nonubuntu_os_pkg.html

What I can recommend to you, if you're lost, is just following the OpenHPC guidelines for xCAT: http://openhpc.community

You'll end up with a proper HPC cluster up and running.

Vinícius Ferrão
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