I have 60+ nearly identical machines that I need to convert to PXE booting. Each has 6 elderly 3TB hard disks. To mitigate the risk of disk drive loss, I need to build a RAID 6 using mdadm. Building the RAID is not a problem, but I need some clues as to how to build the PXE boot image.
I want to boot all the machines off of PXE on a CentOS 7 server using a single image. I have already set up DHCP and DNSMASQ on the server. What I need now is to build a Linux kernel, and OS image that each machine will load into its own RAMDISK. Once booted, the machine will build a RAID 6 using all 6 of its onboard disk drives.
The application is Hadoop, so Ambari needs to be part of the install. I have found that the default CentOS install also needs a bunch of yum updates, so I would like have all these built into the OS image.
All the websites I am finding are about installing a new OS on a local hard disk after PXE booting. I want PXE to build a RAMDISK and load the OS into that. Once its up, I can do the rest.
Where to start?

Hello and welcome to LQ.

There is quite a lot of ways to do this. Not sure which way to suggest.

This is one example using kickstart. https://www.server-world.info/en/not...OS_7&p=pxe&f=3

Might look at backula also and other backup schemes that work with pxe.

Making each system unique may require other changes. Sometimes RH based distros don't fully clone correctly. May have to watch out for unique naming.

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I know that Amazon and all the big cloud hosting providers use PXE to boot their servers. I can't seem to find out exactly how they do that. Those server farms consist of diskless machines, with nice fiber HBA's and some gigEther connections.

My architect tells me that we need not be terribly concerned for which applications reside on which host, hence naming is important but not THAT important. Each host should get its name and IP address from the DHCP server. This should be sufficient so that each host will run a configure_me script at startup.

I don't know Kickstart, but it looks interesting to me. I tried looking at some "Introduction to Kickstart" web pages but I will need to know a lot more than just the introductory stuff. Somebody, someplace has done this and is doing it. I just need some clues as to where to look.