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Re: grub-mkrescue: Problem with MBR partition table at start of EFI part
From: |
Daniel Kiper |
Subject: |
Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition |
Date: |
Mon, 20 May 2019 14:35:55 +0200 |
User-agent: |
NeoMutt/20170113 (1.7.2) |
On Thu, May 16, 2019 at 02:18:51PM +0200, Thomas Schmitt wrote:
> Hi,
>
> i quoted mformat.c:
> > > /* install fake partition table pointing to itself */
>
> Daniel Kiper wrote:
> > OK, but why it is also done for FDD images?
>
> According to its man page, mformat formats floppies. So the question
> would be why it creates a partition table at all.
Yeah, could you ask mformat folks about that?
> > > Either mformat's result is ok or it is not.
>
> > I would say that in most cases it works but is some it does not. This
> > is difficult to say right now where is the bug
>
> Whoever is the culprit when stepping into a pitfall, grub-mkrescue should
> try to avoid known bug triggers.
Yep but on the other hand we have to not break anything which works right now.
> I understand from Vladimir's reply that he did not think of partition
> tables or floppies when employing mformat in grub-mkrescue.c. He wanted
> a FAT filesystem with usual entrails.
> Usual is to have no data in it which look like a partition table entry
> which describes a partition starting at block 0.
> (Microsoft hasn't. The larger Linux distros haven't.)
>
> So i propose the change as fine tuning of the original developer's
> intention. (Vladimir will correct me if i'm wrong.)
After some thinking I have an itching to add the "-k" option to the
mformat. However, I am not convinced that this should go into the
release. There is a chance that we will break other platforms and fix
the only one. So, I would suggest to make this as a known issue and fix
it after the release. Does it make sense?
> > So, first of all I would like to understand why somebody decided to do that
>
> As for the Macbook, my theory is that it tries to explore what it believes
> to be an extended partition. Newer Macbooks are said not to make this
> mistake any more.
>
> As for mtools, binary search on
> http://svn.savannah.gnu.org/viewvc/mtools/trunk/mformat.c?view=log
> yields that the comment came in with revision 4 in line 958
>
> http://svn.savannah.gnu.org/viewvc/mtools/trunk/mformat.c?revision=4&view=markup
> Revision 2, line 800 shows no trace of a partition table until in the
> end 0xaa55 is written.
> Revision 4 is from 2002 and has as commit message "3.9.8, modified files".
>
> Committer is "aknaf", probably the same as "alainknaff" who committed
> to mtools last year.
> https://savannah.gnu.org/users/alainknaff
> Maybe he still can remember why he added the partition entry.
Could you ask him about that? Please keep grub-devel in the loop.
> --------------------------------------------------------------------------
>
> > > After all it is quite easy to override the ideas of grub-mkrescue
> > > before the ISO gets packed up. In practice, it's preference for GPT
> > > makes more problems than its preference for mformat.
>
> > This is not good idea. I would like to see a fix or at least a kind of
> > workaround in GRUB upstream.
>
> I was not happy with Vladimir's decision to use GPT instead of MBR partition
> table. (Because of non-mountable partitions and the GPT backup, which needs
> to be relocated after copying the ISO onto USB stick.)
I am not sure I understand. Which GPT do you refer to?
Daniel
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, (continued)
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, pelzflorian (Florian Pelz), 2019/05/11
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/11
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, pelzflorian (Florian Pelz), 2019/05/11
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/11
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Daniel Kiper, 2019/05/13
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/14
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Daniel Kiper, 2019/05/15
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/15
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Daniel Kiper, 2019/05/16
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/16
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition,
Daniel Kiper <=
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/20
- Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Thomas Schmitt, 2019/05/14
Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Chris Murphy, 2019/05/09
Re: grub-mkrescue: Problem with MBR partition table at start of EFI partition, Michael Schierl, 2019/05/11