Dan Hitt wrote:
> On Thu, Jan 21, 2021 at 3:33 AM Brian <ad44@cityscape.co.uk> wrote:
>
> >
> > menuentry 'Debian 10' {
> > linux /boot/vmlinuz
> > initrd /boot/initrd.gz
> > }
> >
> > --
> > Brian.
> >
> >
> Brian, thanks so much for your advice. Thank you also Felix, David, and
> Bastien --- i need to study what you have all written.
>
> However, Brian's final stanza is so simple that i can ask a question about
> it immediately.
>
> And that is: how can grub2 or any other software know what partition
> '/boot' refers to?
>
> So i presume that in this very very short stanza you provide, there will
> also have to be a search line like David has (search --no-floppy ......) to
> identify just where '/boot' is (???).
https://en.wikipedia.org/wiki/GNU_GRUB#Startup_on_systems_using_BIOS_firmware
stage 2: core.img loads /boot/grub/i386-pc/normal.mod from the
partition configured by grub-install. If the partition index has
changed, GRUB will be unable to find the normal.mod, and
presents the user with the GRUB Rescue prompt.
So the answer to your question is, it's been configured at
install time, not discovered at runtime.
-dsr-
Thanks Dan for your mail, and for the reference to the wikipedia article.
When you say 'configured at install time', does that refer to the time at which i run 'sudo update-grub' (on my mint host)?
(I presume that it is impossible that this refers to the time when grub itself was last installed on the box, several years ago.)
Anyhow, i added an entry to /etc/grub.d just to see what would happen if i took the simple menu entry quite literally:
menuentry "simple-test" {
linux /boot/vmlinuz
initrd /boot/initrd.gz
}
I ran 'sudo update-grub', and the entry was copied into /boot/grub/grub.cfg without modification. And then i tried booting into it, just to see what grub would do. And, it did what i think was the only thing it possibly could: it reported:
error: file `/boot/vmlinuz' not found.
error: you need to load the kernel first.
Press any key to continue...
Now, Brian said that "the installer's initrd does not contain a loop module", so that would indicate that if i want to use debian-10.7.0-amd64-xfce-CD-1.iso, i'll need to get it on the disk (presumably by just unpacking it somewhere --- prior to booting, i can loop mount it and copy it to a 'real' directory), and then modifying /boot/vmlinuz and /boot/initrd.gz to be paths that grub understands. Or, maybe the debootstrap method Bastien suggests would be good.
Anyhow, thanks for your message, and thanks everybody else for these important pieces of knowledge that i need to learn.
dan