Dennis Lee Bieber <[email protected]> wrote:
> On Sat, 12 May 2018 13:46:57 +0100, Chris Green
> <[email protected]> declaimed the following:
> 
> >I have an old BBB with a 2Gb eMMC (A5A) and inadvertently plugged a

(actually an A6A, misread the label)

> >microSD with a 4Gb IOT version of Debian on it.  What should happen?
> >
>         If the contents of the eMMC are really old, it likely doesn't even 
> look
> at the SD card unless you hold down the alternate boot button.
> 
>         If the contents are rather modern, it may run uBoot from the eMMC and
> then transition to the SD card (and that could fail if the eMMC uBoot
> expects late [kernel] loading of device tree overlays, but the SD card
> expects early [uBoot] device tree loading).
> 
They're both modern as I'd already (after some hassle due the above
things you've noted) getting a Debian 9.4 console installed into the
eMMC.  I was only trying to check whether the IOT image was good, I
didn't actually want it on the BBB.  It's just a spare BBB, not being
used for anything at the moment.
> >I *think* it's simply running from the microSD card which seems quite
> >sensible.  Is there an easy way of telling what memory it's running
> >from?
> >
>         Well, given the memory sizes, a quick test would just be to do "df"
> from a console connection, and seeing what the largest partition comes up
> as. Or try "uname -a" on the assumption that the SD card has a much newer
> OS.
> 
Yes, that's sort of how I concluded that it must be running from the
microSD but I wondered if there was a more definite way.


>         Or, maybe... closely observe the blinkenlights... One identifies mmc0
> activity, and another mmc1 activity (now -- which is considered 0 and 1 is
> an exercise for the user; I have a vague memory that at one point in the
> past, 0 and 1 depended upon which device was used for booting, and was not
> fixed to eMMC vs SD).
> 
Yes, I don't think the mmc0/mmc1 thing helps much, they seem not to
relate spcifically to eMMC and microSD - which is a pity.

Thanks for all the ideas.

-- 
Chris Green
ยท

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