If you are interested in booting your Raspberry Pi 4 without local storage, this guide can help you accomplish it. While most tutorials cover how to do this with NFS, this one uses iSCSI. Additionally, with the latest firmware update for the Pi 4 (as of 2020-04-16), setting up network booting is much simpler. Other guides require modifying the local DHCP server or spinning up a proxy DHCP server t