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Re: Booting a CF or SD card from an internal card reader



On Fri 05 May 2017 at 13:53:00 -0400, Stefan Monnier wrote:

> >> Of course it all depends on what you mean by "booting from".  AFAICT in
> >> Leandro's situation, he's loading Grub from some other disk (probably
> >> the main HDD or SSD), so he's already "not booting from the SD card" in
> >> this sense.
> > By "booting from" I mean everything which is needed to bring the OS up
> > is located on the SD or CF card.
> 
> AFAIK in his case, Grub itself is already on another device because the
> BIOS can't boot directly from the SD card.  So, he can't "boot from" his
> SD card using your definition.

Indeed. I thought I had highlighted that a few times, but maybe not.
GRUB doesn't see a card reader on a PCI bus.
> 
> > In essence, the card can be transferred to to another machine and will
> > still boot. What you describe below I'd refer to as "booting into the
> > OS" ; it cannoot be done without the assistance of software on the
> > machine itself.  I hope this is not an artificial distinction.
> 
> I fully agree: I myself tried to setup a "rescue USB key" that could
> boot everywhere, but that simply can't work on those machines whose
> BIOS simply doesn't know how to boot from USB.

GRUB's nativedisk could help with this. It does on my machines which
don't know how to boot from USB.

> > In principle this is a viable booting method but there are issues to be
> > aware of.
> 
> Oh, yes.
> 
> > The kernel on the main HDD or SSD is unlikely to be the Tails
> > kernel so a third device would be needed to hold such a kernel;
> 
> You don't need a third device.  You need to consciously/carefully save
> your Tails kernel and initrd somewhere on the HDD/SSD.  You can use
> a separate "TAILS-BOOT" partition on that HDD/SSD for that, or you can
> place them in "the normal partition" but under a special name like
> "vmlinuz-tails" and "inird.img-tails".

Fair enough.
 
> > The OP in the original thread actually booted in this way from the hard
> > disk, but (as it fortuitously happened) kernel, initrd and OS on hard
> > disk and SD card were identical.
> 
> That must have been "beginner's luck", indeed.

I've done the same myself. It works. Great! Then I've discovered the
special circumstances in which the procedure was carried out. Usually
when something goes wrong.

(Totally off-topic: I use the dialog utility with a gauge widget. After
many years the script using it stopped working. I read the manual. It
has "integer" in it for the section on gauge. One word made all the
difference between a working and non-working script. The new input I
have now has no integer values. No wonder the script didn't work).

Aren't Debian computers wonderful? :)

-- 
Brian.


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