[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: ISO installer image: GPT versus MBR partitions
From: |
Thomas Schmitt |
Subject: |
Re: ISO installer image: GPT versus MBR partitions |
Date: |
Sun, 21 Apr 2019 14:27:10 +0200 |
Hi,
i wrote:
> > ... 3f 0b
> > ... 40 0b
> > ... == ==
Florian Pelz wrote:
> Why is 0b underlined?
Too much enthusiasm on my side.
> OK, so I just wrote the Guix git master with ludo’s reproducibility
> patches to a USB drive (boot gets stuck again) and then did:
> sudo dd if=/dev/sdc2 of=mysdc2.img
> When I open it with ghex, I find at position 446:
> 80 00 00 04 01 24 4f 00 00 00 00 80 16 00 00 00
Pinching eyes ...
Bootable flag is set.
Start C/H/S is 4/0/0. (x/y/1 is usual)
Partition type is 1.
End C/H/S is 1/36/15.
Start LBA is 0x80000000 = 2,147,483,648.
Block count is 0x16 = 22.
So what ever did you do to this mysdc2.img ?
> I change it to
> 80 00 02 00 01 01 12 4f 01 00 00 00 3f 0b 00 00
> I dd the changed mysdc2.img back to /dev/sdc2.
>
> Now it boots. :)
Start C/H/S is 0/0/2.
Partition type is 1.
End C/H/S ... i'm getting too old for decoding MBR C/H/S bit fields.
Start LBA is 1.
Block count is 0x0b3f = 2879.
So Start LBA 0 is indeed the trigger of the problem.
As soon as the partition entry does not point to its hosting block any
more, the (now very probable) loop in EFI cannot happen.
> Strangely, I now have only one entry “GRUB 2.02” in
> the boot selection, but “EFI Boot” (or what it was called) is gone.
What do you see if the partition entry is zeroized entirely ?
(Elsewise i refer to the Futurama quote in my previous mail.)
> Is it a good
> idea to add -k to mformat in grub-mkrescue for the upcoming Guix 1.0
> release (even though you don’t like it)?
We need to ask at grub-devel. I have begun to compose a mail.
You will be Cc-ed.
Does guix-devel want to be Cc-ed ?
New mail:
> MacBook Pro (13-inch, Mid 2010)
> Model Name: MacBook Pro
> Model Identifier: MacBookPro7,1
> Boot ROM Version: MBP71.003F.B00
> SMC Version (system): 1.62f7
I will put this into my mail to grub-devel.
> Serial Number ...
... but this only if asked for.
Back to old mail:
> Or should mformat be patched instead? Could any of
> this be upstreamed?
That's why i asked Ludovic about our chances with mtools upstream.
I would propose an option to write the usual pseudo-MBR but without that
partition entry.
(Well, maybe somebody there can even remember why a partition entry
is made by default.)
> What about your MBR repacking?
I will create an option for zeroizing bytes 446 to 461 of the EFI image.
When the dust has settled here, i will ask Ludovic for preparing the
ISO production code for a run with libisoburn's wrapper script
frontend/grub-mkrescue-sed.sh for MBR-only.
At that occasion, the EFI image repairer could be tested, too.
The script has a mode "original" which does not change the xorriso
options submitted by grub-mkrescue. So it produces original GPT.
(It's original purpose is spying on grub-mkrescue's xorriso options.)
> I just doing what I’m told, but I
> don’t quite understand what I’m doing here.
We had a wild ride over boot sectors and partition tables.
I collect my knowledge in libisofs file doc/boot_sectors.txt .
At days when our web certificates are valid, it is available at
https://dev.lovelyhq.com/libburnia/libisofs/raw/master/doc/boot_sectors.txt
Hah. Bug #4. No doc/boot_sectors.txt in libisofs tarball.
But it is in GNU xorriso's tarball:
https://fossies.org/linux/misc/xorriso-1.5.1.tar.gz/xorriso-1.5.1/doc/boot_sectors.txt
For completeness, a reserve address for my grub-mkrescue-xorriso wrapper:
https://sources.debian.org/src/libisoburn/1.5.0-1/frontend/grub-mkrescue-sed.sh
Have a nice day :)
Thomas
- Re: ISO installer image: GPT versus MBR partitions, (continued)
- Re: ISO installer image: GPT versus MBR partitions, Thomas Schmitt, 2019/04/20
- Re: ISO installer image: GPT versus MBR partitions, pelzflorian (Florian Pelz), 2019/04/20
- Re: ISO installer image: GPT versus MBR partitions, pelzflorian (Florian Pelz), 2019/04/20
- Re: ISO installer image: GPT versus MBR partitions, pelzflorian (Florian Pelz), 2019/04/20
- Re: ISO installer image: GPT versus MBR partitions, Thomas Schmitt, 2019/04/20
- Re: ISO installer image: GPT versus MBR partitions, pelzflorian (Florian Pelz), 2019/04/21
- Re: ISO installer image: GPT versus MBR partitions, Thomas Schmitt, 2019/04/21
- Re: ISO installer image: GPT versus MBR partitions, pelzflorian (Florian Pelz), 2019/04/21
- Re: ISO installer image: GPT versus MBR partitions, Thomas Schmitt, 2019/04/21
- Re: ISO installer image: GPT versus MBR partitions, pelzflorian (Florian Pelz), 2019/04/21
- Re: ISO installer image: GPT versus MBR partitions,
Thomas Schmitt <=
- Re: ISO installer image: GPT versus MBR partitions, pelzflorian (Florian Pelz), 2019/04/21
- Re: ISO installer image: GPT versus MBR partitions, Thomas Schmitt, 2019/04/21
- Re: ISO installer image: GPT versus MBR partitions, Thomas Schmitt, 2019/04/22
- Re: ISO installer image: GPT versus MBR partitions, pelzflorian (Florian Pelz), 2019/04/23
- Re: ISO installer image: GPT versus MBR partitions, Thomas Schmitt, 2019/04/23
- Re: ISO installer image: GPT versus MBR partitions, Ludovic Courtès, 2019/04/17
- Re: ISO installer image: GPT versus MBR partitions, pelzflorian (Florian Pelz), 2019/04/17
Re: ISO installer image: GPT versus MBR partitions, Thomas Schmitt, 2019/04/23