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From: The Natural Philosopher <tnp@invalid.invalid>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: How to boot from SD but run from USB?
Date: Fri, 24 Jan 2025 14:11:11 +0000
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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.




-- 
Climate Change: Socialism wearing a lab coat.