[PLUG] Anyone can still remember Grub2 insides?

tomas.kuchta.lists at gmail.com tomas.kuchta.lists at gmail.com
Tue Jun 16 22:08:37 UTC 2020


Thanks Don, Bill

Strange evolution ate my email - will try again:

I completely missed grub2-set-default - I probable was not root when hitting tab
to list all grub2-* commands. Using it would probably made me realize that my
edits to /boot/grub/grub.cfg are not the issue.

I have since discovered that what I was looking at was not grub2 boot menu but
syslinux menu. Modifying syslinux isolinux.cfg config did what I intended. Or ..
was it syslinux? I am not 100% sure because the menu definitely looked like
grub2 config - it just seems to respond to isolinux.cfg config changes.

In any case - because this is installation media - it tries to present uniform
boot menu in different systems BIOS/EFI with different media CD/USB. grub2 and
EFI menus are definitely defined as well as syslinux. I guess that I have more
testing to do to understand what is being used and when.

The distro, in this case, is opensuse. The install media boot mechanics is not
described in great detail anywhere. Every time I had to dive into this - it was
pain - not many people understand this anymore - it was developed decades ago at
this point - so there is a lot of useless, garbage info on the web.

I asked on opensuse mailing list first, but you know, experts are busy doing,
not wandering around mailing lists - eager to describe this for the millionth
time since 1990s.

Tomas
 
On Tue, 2020-06-16 at 20:26 +0000, Don Buchholz wrote:
> Hi Tomas,
> 
> With regards to changing config file:
>   1) Which distro?
>   2)  "Legacy BIOS" or "EFI" boot mode?
> 
> With regards to setting default:
>    1)  See man page for grub2-set-default(8).
> 
> - Don
> 
> ________________________________
> From: plug-bounces at pdxlinux.org <plug-bounces at pdxlinux.org> on behalf of tomas
> .kuchta.lists at gmail.com <tomas.kuchta.lists at gmail.com>
> Sent: Monday, June 15, 2020 8:52 PM
> To: Portland Linux/Unix Group <plug at pdxlinux.org>
> Subject: Re: [PLUG] Anyone can still remember Grub2 insides?
> 
> Thanks Bill,
> 
> No, I did not try /boot/grub/custom.cfg - in my case - that would not help.
> 
> I did not say this in my original post - the changes I need to make are
> trivial,
> but involve changing current menu rather than adding to it:
> * changing default menu item and adding a few kernel boot options to it
> 
> I know - I am also a victim of - the whole world is about how to boot/install
> cloud instances or containers.
> 
> Tomas
> 
> On Mon, 2020-06-15 at 07:08 -0500, Bill Barry wrote:
> > On Mon, Jun 15, 2020 at 1:13 AM <tomas.kuchta.lists at gmail.com> wrote:
> > > 
> > > Hi,
> > > 
> > > I have forgotten grub2 internals since I needed them 5 years ago - Grub
> > > documentation is not great outside normal usage.
> > > 
> > > Can anyone give me a hand here.
> > > 
> > > I want to modify Grub2 menu in a linux installation media - under mounted
> > > /boot/grub.cfg
> > > The installation media does not have /etc/grub.d - so, I cannot make
> > > changes
> > > in
> > > /etc and use chroot grub2-mkconfig to apply the change.
> > > 
> > > Editing the /boot/grub.cfg has no effect.
> > > 
> > > Thanks,
> > > Tomas
> > > 
> > 
> > Have you tried making  the changes in /boot/grub/custom.cfg
> > https://wiki.archlinux.org/index.php/GRUB
> > 
> > Bill
> > _______________________________________________
> > PLUG mailing list
> > PLUG at pdxlinux.org
> > http://lists.pdxlinux.org/mailman/listinfo/plug
> 
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