Re: grub2 doesn't know of eSATA on some computers?

[Jordan Uggla]

On Wed, Sep 3, 2014 at 12:39 AM, Zhang Weiwu <address@hidden> wrote:
> grub> root (hd1
>
> Result: nothing. In fact, if I do tab-completion at
> grub> root (hd
>
> without typing '1', it autocompletes to hd0, meaning grub2 consider only one
> hdd in existance.

The standard way to list devices at the grub shell is to simply run "ls".
>
> My question:
>
> Is it by design some laptops won't let grub2 boot from eSATA - a dead-end,
> or merely a configuration issue? The laptop is Toshiba Portégé R600 with
> very limited BIOS options (no config option about eSATA at all and harddisk
> does not show up in BOIS once installed or connected).

By default grub accesses disks through your boot firmware's interfaces
rather than directly, what this means is that (by default) grub can
only access the disks that your BIOS can access.

GRUB does have native drivers for some types of hardware but 1: I
don't think (though I have not checked) that eSATA is among the
supported hardware interfaces. 2: If using grub's native drivers you
cannot chainload, and it is only possible to boot Windows by
chainloading its bootoader. and 3: Even if you were able to chainload
Windows' bootloader, and had proper int13 hooks to allow Windows'
bootloader to access your eSATA disk, Windows itself would still need
to support booting via eSATA (I don't know what is involved in setting
this up for Windows).

So it can't easily be done, but you do have some options that *may* work.

1: Find a boot manager that can add support for additional hardware
types via int13 hooks, like Plop, but with eSATA support (as far as I
can tell, Plop does *not* have eSATA support). I don't know if such a
boot manager even exists.

2: Keep just your (very small) Windows "System" partition on your SSD,
while leaving the Windows "Boot" partition on the eSATA drive. Note
that Microsoft's terminology is opposite of what you probably expect
for "System" and "Boot", see
http://en.wikipedia.org/wiki/System_partition_and_boot_partition . I
don't know if Windows allows the System and Boot partitions to be on
different drives, and you still need to configure Windows properly to
boot via eSATA. Accomplishing this is likely not straightforward. Just
copying the file contents of the System partition to another ntfs
filesystem in a partition on your SSD certainly won't work. Using dd
or GParted to copy the partition's contents to a partition on your SSD
probably won't either. You'll need to ask Windows support for
instructions on how to accomplish this, if it's possible at all. The
good news is that once Windows is configured properly, all you have to
do from grub's side is re-run update-grub or "grub-mkconfig -o
/boot/grub/grub.cfg".

Good luck.

-- 
Jordan Uggla (Jordan_U on irc.freenode.net)