Re: Set a bootdrive environment variable.

[Andrei Borzenkov <arvidjaar@gmail.com>]

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В Thu, 04 Jun 2015 17:40:01 +0200
Vladimir 'φ-coder/phcoder' Serbinenko <phcoder@gmail.com> пишет:

> What's the problem with extracting this from $prefix ? This seems to be
> a better match if what you want is location of GRUB.

The original problem was that this information was needed to set
$prefix so it cannot be extracted from it :)

It can be extracted from $cmdpath but then it requires regexp in early
config and feels backwards in general.

> On 31.05.2015 08:42, Andrei Borzenkov wrote:
> > В Wed, 27 May 2015 08:55:09 -0400
> > Mathieu Trudel-Lapierre <mathieu.tl@gmail.com> пишет:
> > 
> >> On Wed, May 27, 2015 at 12:04 AM, Andrei Borzenkov <arvidjaar@gmail.com>
> >> wrote:
> >>
> >>> В Tue, 26 May 2015 12:46:07 -0400
> >>> Mathieu Trudel-Lapierre <mathieu.tl@gmail.com> пишет:
> >>>
> >>>> I've been playing with fixing Ubuntu bug 1097570; trying to debug a
> >>> script we
> >>>> use for the EFI images which detects where to boot from based on the
> >>> location
> >>>> of a .disk/info file.
> >>>>
> >>>> Turns out this mostly works, except for the fact that grub appears to
> >>> always
> >>>> list devices in a specific order, which interferes with the detection if
> >>> more
> >>>> than one device contains that file.
> >>>>
> >>>> I think I can make this work appropriately provided we:
> >>>>   - Use hints for search --file;
> >>>>   - Have some value to pass to --hint= designating the boot drive.
> >>>>
> >>>
> >>> If you always want to use the same device GRUB was booted from why do
> >>> you need to search for anything at all?
> >>>
> >>
> >> My understanding from why the search was used is that $root may not have
> >> been set for all types of devices (i.e. CDs), and the same built grub
> >> images (for EFI) were used on bootable USB and CDs since they are both
> >> built from a single ISO.
> >>
> > 
> > That depends on your image. If image defines prefix and drive and/or
> > partition is missing (e.g. (,msdos1)) missing parts are derived from
> > whatever firmware provides (effectively what ends up in $cmdpath) and
> > should be set for any boot media.
> > 
> > Although I just hit a system (Fujitsu Lifebook S761) which passes bogus
> > device path to image that does not match any existing handle, so both
> > $cmdpath and $root are not set.
> > 
> >> In retrospect, having a properly set $cmdpath (or $grub_bootdev or
> >> whatever), probably makes this unnecessary.
> >>
> >>
> >>>> Included is a patch that adds a "bootdrive" variable alongside cmdpath;
> >>> which
> >>>> contains just the drive designation for the boot device, to be used as
> >>> such:
> >>>>
> >>>> search --set=root --hint=$bootdrive --file .disk/info
> >>>>
> >>>> I'd much appreciate review on that patch :)
> >>>>
> >>>
> >>> You can extract it from $cmdpath using regexp already. In retrospect
> >>> having separate variables for device and path would be more flexible;
> >>> but $drive is not appropriate name as it can refer to network as well.
> >>> Something like $grub_bootdev and $grub_bootpath.
> >>>
> >>
> >> That was one of the reasons I wanted review on it, so thanks!
> >>
> >> I'm happy to change it to $grub_bootdev or whatever else if we feel having
> >> separate variable for this in indeed a good idea (and I'll add what's
> >> needed to get $grub_bootpath).
> >>
> > 
> > The problem is that $cmdpath had been around for long enough. If
> > $cmdpath is used only after loading normal (that are cases I'm aware
> > of) we can make it compatibility variable set by normal without causing
> > more core bloat.
> > 
> >>
> >> Mathieu Trudel-Lapierre <mathieu.tl@gmail.com>
> >> Freenode: cyphermox, Jabber: mathieu.tl@gmail.com
> >> 4096R/EE018C93 1967 8F7D 03A1 8F38 732E  FF82 C126 33E1 EE01 8C93
> > 
> > 
> > _______________________________________________
> > Grub-devel mailing list
> > Grub-devel@gnu.org
> > https://lists.gnu.org/mailman/listinfo/grub-devel
> > 
> 
> 


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