[Tdog]

I have a dual boot system on a Dell Mini 10v, SL 10.6.6 & Ubuntu Netbook 10.10. The HD is partitioned like this:

sda1: System/Boot Partition
sda2: OS X (10.6.6)
sda3: Ubuntu partition. GRUB bootloader installed here.
sda4: Linux Swap
sda5: FAT32, for shared data

I've been using this about 6 months, but twice now I have selected the Linux partition from Chameleon & been unable to boot Ubuntu. I get this GRUB error instead:

error: no such partition.
grub rescue>

running the set command returns this, which seems correct:
prefix=(hd0,gpt3)/boot/grub
root=hd0,gpt3

If I run Ubuntu Live off a USB drive, I can see the partition, mount it & browse it. The file system looks intact. I've tried booting off the Ubuntu Alternate CD & running Rescue Mode to reinstall the GRUB boot loader, but this operation fails, saying: "Executing 'grub-install' /dev/sda3/' failed."

I ran the Boot Info Script & it reports this boot sector info for my Ubuntu partition: "Grub 2 is installed in the boot sector of sda3 and looks at sector 903373787 of the same hard drive for core.img, but core.img can not be found at this location."

Since I haven't figured out a way to repair this problem, I do a complete re-install of Ubuntu, but I'm wondering if others have found a solution. Maybe there is a problem with GRUB being installed on a partition. A note in the GRUB manual says:

If possible, it is generally best to avoid installing GRUB to a partition (unless it is a special partition for the use of GRUB alone, such as the BIOS Boot Partition used on GPT). Doing this means that GRUB may stop being able to read its core image due to a file system moving blocks around, such as while defragmenting, running checks, or even during normal operation.

Dell Mini 10v | Mac OS X 10.6.6 | Ubuntu Netbook 10.10 | 1.6 GHz | 1GB RAM | 500GB HDD | BIOS A06 | NBI 0.8.4 RC1

[pokenguyen]

I've got the same problem, I'm triple-boot Mac, Windows and Mint Linux and now I can't boot to Linux any more. I'm going to install Jolicloud over Linux mint for testing purpose.

[Oscar]

well, i had the same trouble... and was able to fix it all by following the instructions here: Re:Did you SCREW your Grub? Now stuck in Grub Rescue? - Linux.com: Linux Forums | Linux.com

just make sure you pick the right partition.

cheers.

[Tdog]

Well I gave those instructions a go. After running this command:

sudo grub-install --root-directory=/mnt/ /dev/sda

I get this error:

/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: if you really want blocklists, use --force.

The message makes sense, since I am using GPT, not MBR, for the partition table. I probably don't want to use blocklists, which is probably what caused the problem in the 1st place. According to one page I found:

Blocklists are the alternative used by GRUB when embedding is not possible. In this scheme, GRUB leaves core.img in the filesystem (in /boot/grub/). Then it makes a list of all blocks that compose this file. The list itself, much shorter than core.img, will be used during boot to recompose core.img and load it into memory. The problem with this scheme is that there are many situations in which it can break. Once a file is put in your filesystem, there's no guarantee the blocks won't ever be relocated. It can happen with some filesystem features (e.g. tail packing), or with some administration activities (e.g. resizing or copying a filesystem), or simply because of aggressive fsck techniques.

There's a thing called a BIOS Boot Partition, though, so I'm thinking that the next thing to try is to add yet another partition, tag it "bios_grub", & re-install Ubuntu. During the install, I'm hoping I can specify that the boot loader be installed on the new partition.

[Oscar]

Yes, if you re-install you can (and should) specify where to install grub. Not sure where that is in ubuntu in the current version. Ubuntu 9.04 had it in step #7, there was a button that said "Advanced."
Might still be in the same spot.

[Tdog]

I added a small EXT4 partition, tagged it "bios_grub" & ran the Ubuntu Desktop 10.10 install. Using the "specify partitions manually" option, I can specify where to put the boot loader. After the install ran without complaints, I booted up the machine, but the Chamelon boot loader did not offer me a choice of a Linux partition to boot anymore. It did not look like the Grub boot loader got installed properly. I attempted to install it manually again, but I seem to have goofed that up & the Grub loader may have wiped up Chameleon, making it everything inaccessible. At this point I may just start from scratch again.

[Tdog]

OK, after restoring my OS X boot, I again tried installing Ubuntu 10.10, using a small partition just for the GRUB boot loader. Before running the Ubuntu install, I added a 100MB partition, formatted it as ext4 & did not apply any special flags. During the installation process, I selected "specify partitions manually", which gave me the option to select this for the boot loader. After the install finished, I got to select a linux volume from the Chameleon boot, so this seems to have worked. According to GParted, less than 1MB of the Grub boot partition was used.

In the coming months of use, I'll see if this prevents the Grub error...

[Tdog]

Well, I was OK up until I upgraded my OS X to 10.6.7, after which was I back to the "error: no such partition." message when I selected the Linux icon from Chameleon. My guess is that running the upgrade process or running NBI hosed my Ubuntu boot. I re-installed Ubuntu Desktop 10.10 at this point.