Web lists-archives.com

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




On Tue 18 Apr 2017 at 20:32:38 +0200, Pascal Hambourg wrote:

> Le 17/04/2017 à 21:05, Brian a écrit :
> >On Mon 17 Apr 2017 at 08:48:50 +0000, Curt wrote:
> >
> >>On 2017-04-17, David Wright <deblis@xxxxxxxxxxxxxxxxx> wrote:
> >>>
> >>>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.
> >>
> >>I have an Acer X1430 with an internal "Multi-in-1 Media Card Reader" for
> >>which an SD card inserted into the reader is recognized by the kernel as
> >>as a /dev/sdX disk.
> >
> >You have to be careful here to distinguish between what the OS can
> >recognise and what GRUB can see. The kernel will be using the Multimedia
> >Card device drivers to detect the device
> 
> Not always. If the card reader identifies itself as a generic USB mass
> storage device, then the kernel will use the same drivers as for USB drives
> and assign the same kind of name /dev/sd*. It seems that in this case, most
> BIOS recognize it and can boot from it.
> 
> I guess that the kernel will use MMC device drivers only if the card reader
> identifies itself as a native SD/MMC card reader.

Seems reasonable and sensible. However, my main point was that the kernel
identifying a card as a /dev/sdX disk does not imply it will necessarily
be visible to GRUB and bootable by it. 

-- 
Brian.