Re: GRUB -- Debian overrides? Or maybe I just don't understand it well...
On Tue 19 Dec 2023 at 21:40:19 (-0500), Felix Miata wrote:
> Mark Fletcher composed on 2023-12-20 00:28 (UTC):
>
> > I am curious to know from Debian
> > GRUBbers (as it were) if the behaviour I am describing in this thread
> > is expected...
>
> I suspect few if any regulars here spend much time with Slackware. I think a more
> conventional approach would be to reconfigure Slackware to boot by UUID, with the
> result that Debian's os-prober should pick it up in the more reliable fashion. I
> don't have a bootloader installed on my only Slackware, and have no more
> familiarity with ELILO than that it seems to be the Slack user favorite
> bootloader. Whether or how well it or its Grub might pick up Debian, or any
> proclivity it may have to usurp boot control from Debian or include stanza(s) for
> Debian, I have no basis for guessing.
I can't see anywhere where the OP claims to have set up LFS for
booting itself, as opposed to being booted from a Debian Grub.
It only says "I have been able to get a grub.cfg including the
LFS system …", which seems to imply LFS has only been set up
as a "foreign" system by a Debian system.
When os-prober runs on my system, a lot of stuff gets logged in
messages, syslog and user.log. The lines that contain the string
"result:" (without the quotes) are interesting. It's evident from
those that have six fields following result: have had their root=
field copied from the foreign system's grub.cfg. (In my case,
"foreign" means a Debian system of the previous release.)
When os-prober writes several clauses into my new grub.cfg's
"### BEGIN /etc/grub.d/30_os-prober ###" section, the references
to the partition are constructed using UUIDs (not PARTUUIDs, because
there's an initrd). However, the kernel command line reads
"root=LABEL=toto04", so that string wasn't constructed by os-prober,
but copied from the foreign grub.cfg¹.
That suggests to me the probability that whereas +Grub constructs+
the root= strings for the "### BEGIN /etc/grub.d/10_linux ###"
section, +os-prober copies+ the root= strings into the
"### BEGIN /etc/grub.d/30_os-prober ###" section instead.
> If you can keep your Slack kernel (& initrd if using one) generically symlinked
> without much trouble, a stanza you put in /etc/grub.d/41_custom should be able to
> boot Slack from Debian's Grub using your custom stanza containing root=LABEL= or
> root=UUID= without trouble. Same would go for using 07_custom, or custom.cfg with
> 06_custom, to move your custom stanza to the Debian Grub menu's top.
In case it's not clear, "generically symlinked" means that
/vmlinuz is a symlink pointing to the most recent linux-image.
(Similarly for initrd.) I added the following to
/etc/grub.d/07_custom:
menuentry 'My bullseye' $menuentry_id_option 'custom' {
load_video
set gfxpayload=keep
insmod gzio
insmod part_gpt
insmod ext2
search --no-floppy --set=root --label noah03
echo 'Load /vmlinuz …'
linux /vmlinuz root=LABEL=noah03 ro systemd.show_status=true quiet
echo 'Load initial ramdisk /initrd.img …'
initrd /initrd.img
}
¹ After installing a system, upgrading the kernel, or upgrading
Grub, I run a script that converts /all/ the UUIDs in grub.cfg
into LABELs, in this little dance:
cp grub.cfg → grub.cfg-uuids
cp grub.cfg-edited → grub.cfg-old
< grub.cfg filter-script > grub.cfg-edited
cp grub.cfg-edited → grub.cfg
Cheers,
David.
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