ramroot VS zfsUnlocker

Now I can use ramroot and run the whole OS on RAM.

Anyway, I wrote and maintain a guide to make this setup: https://mags.zone/help/arch-usb.html. I also made a package to optionally load everything to RAM during boot: https://github.com/arcmags/ramroot.

I wrote a tool to load root entirely into RAM on Arch. It checks available RAM and prompts on boot.

You could also use the Arch Linux guide above and install Arch Linux on the USB drive, making sure the boot and root partition sizes are less than the amount of ram in the machine you are booting on. Then install ramroot which will load up your system into ram on boot. This will mean the system runs off ram and not USB. If you need to make changes, install applications or update, you could boot it normally so it runs off USB as any changes won't be saved if it is booted into ram. If your home folder is on another partition on the USB, I don't think that is loaded into ram on boot so you can still save files to it and any personalisations should also be kept between boots.

Personally I hate keyfiles and any form of zfs unlocking automation which stores things locally (I suppose TPM cryptography is a good exception). While I use a traditional EFI /boot with systemd-boot (bootctl) I made this initramfs hook so that my machines can dynamically unlock themselves from my vault cluster with a revokable token. Not quite the same approach and if there's no networking a machine could get caught dead in the water for booting back to a password prompt, but it's good enough right now that I use it on everything.

This is my Vault solution for an mkinitcpio-powered initramfs. I use it on my router as well which is a zfs root Arch install handling a good 20 static routes with a stateful firewall.