[clug] booting linux from SD card

Chris Smart clug at christophersmart.com
Sun Jan 26 20:38:55 MST 2014

On 27/01/14 13:26, Eyal Lebedinsky wrote:
> I can see the entry (actually the whole menu) in the output. So this
> whole thing
> is in an nvram on the mobo? This explains how the info survives the
> removal of
> the media. Is the info entered by the fedora installer or by the efi
> BIOS itself?

Yeah, those are entries in the nvram and would have been created by the
Fedora installer (in line with the UEFI spec). As I'm sure you know
BIOS/MBR machine can only execute the bootloader on a single drive (you
can specify which in the BIOS) and you then use that bootloader's
configuration (e.g. grub.conf) to boot any other operating systems
(sometimes chainloading to their bootloader on another partition).

EFI has a built-in bootloader and you can boot anything that's
registered in the nvram (well, in theory they don't need to be
registered as it will walk the ESP). Each OS has their own bootloader in
their own dir, like \EFI\Fedora or \EFI\Windows (yes, backslash, it's a
fat filesystem) on the (usually shared) ESP partition.

Most machines have a quick boot menu, like F12, where you can override
the default device and boot the CD or a different hard drive. On an EFI
machine you can use the same thing to switch between your nvram entries,
and therefore your installed operating systems.


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