[Bug 998097] Re: Grub2 not recognise GPT when presence hybrid MBR
Stas Davydov
stas.davydov at gmail.com
Sun Sep 16 21:55:55 UTC 2012
>> Do you remember which choice you chose at this screen ( http://pix
.toile-libre.org/upload/original/1312973605.png ) when you installed
Ubuntu ?
I have performed manual partition of disk.
I do NOT tring to create dualboot - so it is not like Bug #1050940 .
The only I want is to load Ubuntu on GPT partition in legacy mode.
I have set of problems with it which I identify as limitations (bugs?) in GRUB2 and kernel:
1. ( in grub-install) Grub2 refuse to "grub-install /dev/sda" if protective GPT entry is NOT the first.
This bug could be workarounded with method described in bug 2.
2. ( in grub booting - core.img? )I could do grub-install IF protective GPT entry is the first, and to rearainge order of records in MBR so it become not first - but in this case GRUB failed to detect GPT during booting.
During boot shown:
error: no such partition
grub rescue> ls
(hd0)
3. ( in grub-install) IF I do protective record start from sector 2048 -
then I could install GRUB in "biosdisk" (?) mode but in this case it
installed it data (102 sectors) starting from sector 1 and so corrupt
GPT header. I assume that is stage1.5/core.img data ?
4. ( in kernel?) with setup when GPT protective record is NOT first and starts from sector 2048 kernel not able recognise hybrid partition table. in dmesg I see:
[sda]: unknown partition table
same time gdisk sees correct GPT and hybrid MBR
Most correct approach - will be to resolve bug 2. But guess that reqires re-working ASM code.
For now I am trying diferent approach - boot core.img in biosdisk mode and then load correct module (part_gpt) through (hd0,msdos2) and then perform father actions through (hd0,gptN).
For that I need to find way to force GRUB install it stage1.5 not to sector 1 (resolve bug 3) .
I guess for that needed to tweak (or hack) boot.img to point it to new place of core.img
I could easily migrate stage1.5/core.img to diferent place with "dd" - but I do not know how point that place for stage1/boot.img
I see that size of stage1.5 is 51kB(102 sectors) so if I place it
starting from sector 1901 it will be good enough. Another option is to
use partition gpt12 (EF02) but then either grub must recognise GPT
partition table (see bug 2) or point for stage 1 it location in biosdisk
mode.
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https://bugs.launchpad.net/bugs/998097
Title:
Grub2 not recognise GPT when presence hybrid MBR
Status in “grub2” package in Ubuntu:
New
Bug description:
Root issue:
grub ignore protective GPT record if that record is not the first one in MBR.
Need to correct:
If protective GPT record appears on any place in MBR - grub must consider system as GPT.
I have hybrid GPT/MBR. Hybrid MBR contains protective record 0xEE but that record is NOT first.
Here is output of gdisk (hybrid MBR):
Number Boot Start Sector End Sector Status Code
1 468992 101480447 primary 0x07
2 234375168 234569727 primary 0xEF
3 * 550782882 574927413 primary 0x83
4 1 468991 primary 0xEE
gdisk (GPT):
Number Start (sector) End (sector) Size Code Name
1 2048 206847 100.0 MiB EF00 EFI system partition
2 206848 468991 128.0 MiB 0C01 Microsoft reserved part
3 468992 101480447 48.2 GiB 0700 win7
4 101480448 138344447 17.6 GiB AF00 other
5 390625280 527343615 65.2 GiB 8301 copyfilesWIN7
6 527343616 550780927 11.2 GiB AF00 backupfile
7 581042176 625141759 21.0 GiB 2700 Samsung_diag
8 138344448 234375167 45.8 GiB 0700 DATA
11 574927414 581042175 2.9 GiB 8200
12 234375168 234569727 95.0 MiB EF02 grub
13 550782882 574927413 11.5 GiB 0700 linux
After that it result in such errors:
root at helena:~# grub-install /dev/sda
/usr/sbin/grub-setup: warn: This msdos-style partition label has no post-MBR gap; embedding won't be possible!.
/usr/sbin/grub-setup: warn: Embedding is not possible. GRUB can only be installed in this setup by using blocklists. However, blocklists are UNRELIABLE and their use is discouraged..
/usr/sbin/grub-setup: error: will not proceed with blocklists.
invoking grub-mkconfig manually gives:
root at helena:~# grub-mkconfig -o test.conf
Generating grub.cfg ...
Found linux image: /boot/vmlinuz-3.2.0-24-generic
Found initrd image: /boot/initrd.img-3.2.0-24-generic
Found linux image: /boot/vmlinuz-3.0.0-19-generic
Found initrd image: /boot/initrd.img-3.0.0-19-generic
Found linux image: /boot/vmlinuz-2.6.38-14-generic
Found initrd image: /boot/initrd.img-2.6.38-14-generic
Found linux image: /boot/vmlinuz-2.6.38-8-generic
Found initrd image: /boot/initrd.img-2.6.38-8-generic
Found memtest86+ image: /boot/memtest86+.bin
grub-probe: error: cannot find a GRUB drive for /dev/sda4. Check your device.map.
grub-probe: error: cannot find a GRUB drive for /dev/sda5. Check your device.map.
grub-probe: error: cannot find a GRUB drive for /dev/sda6. Check your device.map.
grub-probe: error: cannot find a GRUB drive for /dev/sda7. Check your device.map.
done
I have tried diferent approach - was removed hybrid MBR (retained only protective record). After that grub-install succeed. After that I have created hybrid MBR (the same as above).
But after reboot I have got "grub rescue" prompt and error: no such partition.
root at helena:~# lsb_release -rd
Description: Ubuntu 12.04 LTS
Release: 12.04
root at helena:~# apt-cache policy grub-pc
grub-pc:
Installed: 1.99-21ubuntu3
Candidate: 1.99-21ubuntu3
Version table:
*** 1.99-21ubuntu3 0
500 http://ua.archive.ubuntu.com/ubuntu/ precise/main amd64 Packages
100 /var/lib/dpkg/status
ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: grub-pc 1.99-21ubuntu3
ProcVersionSignature: Ubuntu 2.6.38-14.58-generic 2.6.38.8
Uname: Linux 2.6.38-14-generic x86_64
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
Date: Fri May 11 17:45:17 2012
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64+mac (20110426)
SourcePackage: grub2
UpgradeStatus: Upgraded to precise on 2012-05-07 (3 days ago)
---
ApportVersion: 2.0.1-0ubuntu13
Architecture: amd64
DistroRelease: Ubuntu 12.04
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed vga=788 initrd=/install/initrd.gz quiet -- debian-installer/language=ru keyboard-configuration/layoutcode=ru
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release amd64+mac (20110426)
Package: ubiquity 2.10.20
PackageArchitecture: amd64
ProcVersionSignature: Ubuntu 3.2.0-30.48-generic 3.2.27
Tags: precise
Uname: Linux 3.2.0-30-generic x86_64
UpgradeStatus: Upgraded to precise on 2012-05-07 (131 days ago)
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