Recently I came by this article on HN: https://www.jeffgeerling.com/blog/2020/im-booting-my-raspberry-pi-4-usb-ssd
Nothing wrong with it or to criticize. It's of course easier and much more streamlined to be able to boot from the board bootloader directly to OS (without SD card), but with the kernel argument root= you basically could do this since forever(?): separating kernel (and initramfs) coming from µSDHC and running the rootFS on an actual harddrive or SSD. Running my owncloud/nextcloud from HD since a couple of years.
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