Am 25.08.2012 13:13, schrieb Florian Philipp:
> Hi list!
> 
> I've just completed migrating my system from one hard disk to another.
> Although the new disk reports 512 byte blocks just like the old one, I
> thought it would be a good idea to re-align the partitions anyway. I've
> done it this way:
> 
> 1. Create new partitions with gparted, at least as large as the old ones
> (rounded up to full MiB).
> 
> 2. `dd` from the old to the new disk.
> 
> 3. `resize2fs` to match the new sizes.
> 
> 4. Install grub ("root (hd1,4); setup (hd1); setup (hd1,4)")
> 
> 4. Swap disks and reboot.
> 
> Unfortunately, the system failed to find the boot loader. There was no
> grub error. The disk was simply skipped, as if it was unformatted.
> 
> The following steps were taken:
> 
> 1. Verified that the `dd`ed partitions were sane.
> 
> 2. Reinstalled grub from live-CD chroots several times.
> 
> 3. Installed grub on a memory stick and booted from that.
> 
> At this point, my partition table looked like this:
> 
> Number  Start   End     Size    Type      File system     Flags
>  1      1049kB  316MB   315MB   primary   ntfs
>  2      316MB   750GB   750GB   extended
>  5      317MB   424MB   107MB   logical   ext2            boot
>  6      425MB   22.4GB  22.0GB  logical   ext3
>  7      22.4GB  28.9GB  6441MB  logical   linux-swap(v1)
>  8      28.9GB  750GB   721GB   logical
> 
> The first logical partition was the boot partition. The first primary
> partition was a laptop-specific recovery partition. This setup was
> identical to the old one except that I removed a primary partition which
> resided /after/ the end of the extended partition.
> 
> At this point, I've reformatted the first primary partition as ext2 and
> moved boot to this partition. This solved my problem.
> 
> Now, my question is: Why does this work and the old solution doesn't?
> Why can't grub boot from a logical partition when it's MiB-aligned? I've
> changed nothing that should affect the MBR. Then why wasn't at least the
> stage 1 detected?
> 
> Thanks in advance!
> Florian Philipp



Turns out, I was wrong in thinking the immediate problem was solved. In
fact, the system just booted of the memory stick without me noticing.
I've now finally solved by re-creating the boot partition without
MiB-alignment, just good old cfdisk. So, the working partition scheme
looks like this:

Number  Start   End     Size    Type      File system     Flags
 1      32.3kB  316MB   316MB   primary   ext2            boot
 2      316MB   750GB   750GB   extended
 5      317MB   424MB   107MB   logical   ext2
 6      425MB   22.4GB  22.0GB  logical   ext3
 7      22.4GB  28.9GB  6441MB  logical   linux-swap(v1)
 8      28.9GB  750GB   721GB   logical

Is there an explanation for this?

Regards,
Florian Philipp

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