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FastTurtle
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PostPosted: Tue Apr 30, 2013 4:53 pm    Post subject: grub2 questions Reply with quote

Due to issues with grub and lilo not handling the PARTUUID= for kernel options, I'm having to deal with grub2, yet grub2 is giving me issues about finding /dev/sdd with a grub bios_boot flag.

I've read the all of the wiki on grub2 along with using the online grub manual at http://www.gnu.org/software/grub/manual/grub.html#Top and am a bit confused

To setup the flash drive, I've used Gpart 0.14 (stable from portage)

I've also used gdisk (gptfdisk 0.84 stable from portage) to examine things

What's happening is that Gparted is presenting GUID info that doesn't match what's being shown by gdisk

Gparted = xxxx-xxxx (It's labeled as the GUID)
gdisk = yyyy-yyyy (it's labeld as the Partition UUID)

Another difference I'm seeing is that although I've set disklabels in Gparted, gptfdisk (gdisk) is not showing them; indicating that they're not showing the same information, causing problems with grub2 probing the drive for it's information.

Gdisk allows me to set a label but they're not the same as what Gparted sets (mke2fs -L). The dif seems to be a GPT Parttitio Labe while Gparted is setting a filesystem label.
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Randy Andy
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PostPosted: Tue Apr 30, 2013 7:33 pm    Post subject: Re: grub2 questions Reply with quote

FastTurtle wrote:
Due to issues with grub and lilo not handling the PARTUUID= for kernel options, I'm having to deal with grub2, yet grub2 is giving me issues about finding /dev/sdd with a grub bios_boot flag.


Hi FastTurtle.

Grub-Legacy could handle this fine, booting from an GPT partitioned drive via the root=PARTUUID= kernel command line parameter.
This works also without involving a initrd, I already tried this successfully the first time on Jul 24, 2011, as you could see in this post here, If you're able to read german: http://forums.gentoo.org/viewtopic-t-882303.html?sid=e562682ec98d48fa214d75a44145df38

Here's a short outcome of this long thread regarding your question:

Some facts how my drive is partitioned:
Code:

gdisk /dev/sdb
GPT fdisk (gdisk) version 0.8.6

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: present

Found valid GPT with protective MBR; using GPT.

Command (? for help): i
Partition number (1-4): 1
Partition GUID code: C12A7328-F81F-11D2-BA4B-00A0C93EC93B (EFI System)
Partition unique GUID: 29884E5A-69FF-42E8-AB7B-0DEB95FB6EA9
First sector: 63 (at 31.5 KiB)
Last sector: 81915434 (at 39.1 GiB)
Partition size: 81915372 sectors (39.1 GiB)
Attribute flags: 0000000000000000
Partition name: 'Linux/Windows data'

Command (? for help): p
Disk /dev/sdb: 976773168 sectors, 465.8 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 0F7425A1-EB79-4B6A-A7F2-1F98F8E7D8A9
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 976773134
Partitions will be aligned on 8-sector boundaries
Total free space is 5099 sectors (2.5 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1              63        81915434   39.1 GiB    EF00  Linux/Windows data
   2        81915435       163830869   39.1 GiB    0700  Linux/Windows data
   3       163830870       245746304   39.1 GiB    0700  Linux/Windows data
   4       245746305       976768064   348.6 GiB   0700  Linux/Windows data

Command (? for help): q

The important fact from above, there are two GUIDs shown, depending on the way you look at.
Possibly that program A shows the Disk identifier (GUID) and program B the Partition GUID which is different and may confuse someone.

The Disk identifier (GUID) or Partition unique GUID is needed for the gub parameter in this way e.g.:
Code:
title=Gentoo Linux (kernel-3.0.0-gentoo-r1 boot-Test über PartUUID mit gdisk unique guid)
root (hd1,0)
kernel /boot/kernel-x86_64-3.0.0-gentoo vga=791 root=PARTUUID=29884E5A-69FF-42E8-AB7B-0DEB95FB6EA9


The Partition unique GUID instead, is for mounting the partion into your fstab, if your prefer this over LABEL or PATH naming.
As you could see from my partition scheme above, for a successful grub-legacy boot, there is no FAT formatted EFI System Partion necessary.

Please don't ask me about GRUB2 related questions. I don't like it and so I don't use it as long as there is no need for me.

Nevertheless much success,

Andy.
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FastTurtle
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PostPosted: Wed May 01, 2013 12:10 am    Post subject: Reply with quote

Randy Andy:

Thanks for showing me exactly what info grub needed/wanted to use for PARTUUID

I'm wondering what I need in place of the root (hd0,0) since this is a live-usb build that'll be plugged into many different systems w/o knowing how the bios will designate the drive.
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