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Re: Possibly erroneous "device not present" message during boot




On Sat 15 Apr 2017 at 23:52:30 (+0200), Pascal Hambourg wrote:
> Le 15/04/2017 à 22:50, David Wright a écrit :
> >On Sat 15 Apr 2017 at 19:14:24 (+0200), Pascal Hambourg wrote:
> >>Le 15/04/2017 à 16:28, David Wright a écrit :
> >>>On Sat 15 Apr 2017 at 11:05:12 (+0200), Pascal Hambourg wrote:
> >>>
> >>>>A SD card reader such as the one the OP has just exposes the SD card
> >>>>as what it is, a SD/MMC card (/dev/mmcblk*).
> >>>
> >>>I assumed that the OP, writing about a laptop, had no card reader,
> >>>and was inserting the SD card directly into the computer.
> >>
> >>How do you name that slot on the laptop or desktop where you insert
> >>the SD card, if not an embedded card reader ?
> >
> >A slot, or an SD slot (as on this Dell), or a micro SD slot.
> 
> Behind the slot is a SD card reader. Lenovo names it a card reader.

Ok, ok. You're angling for congratulations for guessing what
Amazon and I call a card reader is what you prefer to call a
USB-to-SD card adapter.

Congratulations.

> >You seem to have had some difficulty with this part of my post:
> >
> >| It's not clear to me why an SD is being used in this way as the OP
> >| has at last revealed that the computer is unable to boot from an SD
> >| plugged in directly.
> 
> IIUC, at first the OP did not know that the computer was unable to
> boot from the internal SD card reader and discovered it during this
> thread.

_I_ didn't know whether the OP knew, suspected, or guessed one way
or the other when taking the card on approval. The later assertion
could be correct or incorrect: the experiment and observations
aren't reported. Other people in other places have reported
difficulties booting with /dev/mmcblk-style devices so I'm not
optimistic.

I can't experiment with my own hardware because my mmcblk-style
Dell laptop has a fault (which will probably lead to its demise)
meaning that the screen is only occasionally readable for about
one second at a time, and its VGA output is only turned on after
the kernel has loaded. So no CMOS screens, no Boot Menu, and no
Grub menu, as I don't have photographic recall.

> >(Of course, an SD card can be made to look like a
> >| USB stick just by sticking it in a card reader. Then it will boot.)
> 
> Obviously not with the OP's laptop internal card reader, which does
> not make the SD card look like a USB mass storage class device.

In the laptop's slot, it would appear not. If the methodology I
outlined elsewhere in the thread fails, then it would seem that
whatever is behind this slot needs an OS to read the card, whereas
the BIOS can be persuaded to read a USB stick without the need
for any OS.

Oddly, this ancient laptop (Acer) has a slot that makes the SD card
look like a /dev/sdX disk, and the BIOS is happy to boot from it.

Cheers,
David.