OK, not the "minutiae" post yet. That will be one more below (I think). I guess things "roll out", as they develop (evolve?), as some of these boot methods are not very old (about a year and a half). R-pi.org has this documentation for possible boot sequences, but it still seems a bit abstruse and arcane to me. About six months ago I was sniffing around some githubs that were working (5 years ago) on freeing up the VPU/QPU/GPU stuff. I am not sure if it ever became FOSS (to Stallman's standards!). Luckily, as a biologist, nobody holds me to the standards of a FOSS purist, so I can "feel" my way through the ethical morass. (I'll probably end up close to the "purists" perspective, anyway!). Anyway, these guys were "bare metal" and I was feeling bare metal just reading them. I guess I forgot most of it, though, and I certainly didn't get to read all the official documentation on boot modes, since I have just found those, yesterday.
Anyhoo,
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/ and
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/bootflow.md are useful, here.
So, here is an interesting notion :
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/device.md"
USB device boot mode : When this boot mode is activated (usually after a failure to boot from the SD card), the Raspberry Pi puts its USB port into device mode and awaits a USB reset from the host.".
So, all my r-pi zeros (slave/devices) could be "sd-boot failed", then wait for the one that is host, to USB-reset them?
USB Host Bootmode, is unavailable to pi zero, as far as I know?
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bootmodes/host.md .
So, since I ruled out one official method, and identified a possible suitability for another official method, let us focus on the latter:
"Example code showing how the host needs to talk to the Pi can be found here." . Here goes here =>
https://github.com/raspberrypi/usbboot , which is, exactly where I went yesterday, when I got my pi booted to the large-raspberry-black-screen.
Not quite CLI, which, if I am smart enough, I might find today!
So, in the read-me file of usb-boot utility, there is a section "
Running your own (not MSD) build[/u]". I think this is what I want to do. Now, how much do I remember about tinycore initramfs, or for that matter, any initramfs? 6 months ago I read, but definitely forgot by now. Can't remember if arms have an init?
Anyway, perhaps this website will help; seems to deal with the issue of setting up a filesystem for the usb-boot device?
https://dev.webonomic.nl/how-to-run-or-boot-raspbian-on-a-raspberry-pi-zero-without-an-sd-card"March 22nd, 2018 : Then you could burn the image to an USB flash drive, but we gonna do something clever, we gonna setup a loop device.
cd ~
sudo losetup -P /dev/loop0 Downloads/2018-03-13-raspbian-stretch-lite.imgThen we need two mountpoints for the boot and rootfs directories. Let’s create them.
sudo mkdir -p /pi/{boot,root} "
I don't know. I guess I have to read the rest of that post? Unless anybody else out there knows more about what I am doing than I do? If so, please let me know, so I don't break anything.
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