Re: How to boot from SD but run from USB?

On 24/01/2025 13:43, Chris Green wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

On 24/01/2025 12:55, Chris Green wrote:

The Natural Philosopher <tnp@invalid.invalid> wrote:

>
But frankly its almost always easier to install everything on the USB
drive and remove the SDcard altogether.
>

As I understand it that's not possible with Pi before Pi 2 version 1.2
or something like that.  Basically Pi 3 and onwards can simply boot
from USB, earlier ones can't.
>

>
Yes, that is my understanding also. I think there was a time when you
had to boot from SD and run a comm,and to change a flag in the firmware
to allow USB only boot.
>
I have a Pi 4B and its supremely ecstatic booting from USB. And it's a
totally simple setup
>

Yes, but my original question was (intended anyway) about booting an
early Pi such that it actually runs from USB after booting from the SD
card so that SD card wear isn't an issue.
 

Well I think that has been covered adequately  as well.
Hack the boot partition on the SD card to tell it to use the USB for booting and hack the fstab entry to tell it to remount the USB as root after booting. Or a combination thereof
The SD card VFAT partition will remain mounted on /boot/firmware and so can be upgraded automagically
If it has bootcode.bin it should look at the USB to boot from.
Which works with middle aged pis.
Late models I believe don't need bootcode.bin. Very early models cant boot USB.
There  you have no option but to boot onto the SDcard and edit the SDCARD /etc/fstab to remount the USB drive as root.
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Climate Change: Socialism wearing a lab coat.