Then burn this to a micro SD card. Upon first boot it will auto start and prompt for the necessary configuration info.
It will set up a static IP adress, change the SSH port, set up mount points for the data SSD and Backup SSD, if you want it will format the DATA SSD.
When finished, after a reboot, you have a complete headless server ready to go.
If you want to experiment with setting up your own rpi headless server, install the package from here.
sudo pacman -S eos-hooks
Pudge
EDIT:
I just checked my RPi headless server, and the eos-hooks package is not installed.
Here is the PKGBUILD for eos-hooks.
Thanks @Pudge. Do the EOS config scripts set any configs in the eeprom & config.txt file? I’ve got everything set up & working, but I set some params in the aforementioned as part of the setup (mostly because the Argon ONE manual told me to). I’m not sure it would have been able to boot from the SSD without them.