I am installing CentOS over the top of ubuntu on my Protectli 4-port Vault Mini PC.

Downloading

I downloaded a “minimal” ISO of centos from the CentOS Download page. The CentOS Wiki has these instructions that show I can copy this to my usb key with dd.

So, where is my USB key mounted?

lsblk -p

Mine is /dev/sdb.

sudo dd if=/home/nackjicholson/Downloads/CentOS-8.2.2004-x86_64-minimal.iso of=/dev/sdb

That takes a while, then you can eject it

sudo eject /dev/sdb

Shut down my vault, put the USB key in and follow the Protectli CentOS Install Docs.