Booting a Raspberry Pi from USB (was: Re: Is it a brick?)

[Gene Heskett]

On Monday 11 October 2021 14:28:24 Liam Proven wrote:

> On Mon, 11 Oct 2021 at 18:48, Gene Heskett <gheskett at shentel.net> 
wrote:
> > > Balena Etcher is big but it does the job, it's current and it's
> > > totally free.
> >
> > And so far for me Liam, on rpi3-4 micro-sd's, has been a total it
> > won't boot failure. Makeing usb bootable keys has not been tried,
> > the pi's I have, have ignored the command to make them boot from
> > anything but the micro-sd. Asking questions about it on their forum
> > is verboten and is ignored. Asking again gets your ipv4 address
> > blocked.
>
> I found that a bit hard to follow due to lack of trimming (are you
> using a phone?)... You mean Balena Etcher has failed to write bootable
> USB keys for a RasPi 3?

Never tried. It was originally, when the pi3b was relatively new yet, 
recommended I write the sd card with it, which upchucked before it was 
done, and never made a bootable u-sd.  DD just worked, that got me 
booted into raspbian. But the stock raspbian kernel's latency was 
millisecond plus. Totally unusable. And you could watch the screen being 
redrawn.  This was on a pi3. Eventually a new enough preempt-rt kernal 
came out that did support its video, so I stripped it to armv7 stuff and 
built it on the pi, took around 10 hours. By then I had been banned from 
their forum so I was on my own, so I took the boot stuff apart to see 
what I needed to run the preempt-rt kernel. Made a partition on an SSD, 
and populated it with the stuff it needed, and made a tarball of it, 
just under 30 megs uncompressed. Wash, rinse, and repeat from wheezy, 
jessie, stretch and now buster versions of raspbian.

Exported that tarball, generated on the pi, to one of my linux pc's where 
I had a card writer. Extracted the u-sd from the pi and plugged it into 
the card reader, unpacked that tarball to it, overwriting anything that 
was in the way. Sync'd the card and ejected it, took it back to the pi3, 
booted flawlessly. Decent latency in the sub 50 microsecond category. 
Ran my lathe with it that way for a couple years. But the pi3b was 
dragging its tongue on the floor doing it.

Then the pi4b came out so I ordered a 2g version. Changed the kernel for 
the new gpio setup, and repeated that install. That was February last 
year. pi4 is a hell of a lot faster, and it all Just Works. I know you 
can make debs that will install a new kernel, but despite asking how to 
do that, I was banned for asking.

But on the pi4b with usb3 interfaces to the SSD's, I can build a new 
kernel in about an hour.

And its latency, running overnight to collect the absolute worst case is 
around 50 microseconds unless I start firefox, normal is about 12 
microseconds. Not too shabby for a computer that according to a 
kilawatt, is running on 8 watts.  The monitor draws 11 watts.

Take care Liam. I Hope I haven't bored you too much. ;o)

Cheers, Gene Heskett.
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author, 1940)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>