On Fri, Apr 12, 2013 at 12:39:47AM -0500, g wrote:
> 
> as for your writing grub to the usb memory stick, how is grub installer
> being called?
> 

There is an eternal confusion.

The BIOS order disk is 0x80, 0x81, etc. (0x0, 0x1 are the A: and B: floppies if I remember right).

This is all that GRUB can know about, *and* they get it right - by referring to (hd0), (hd1), etc.

The BIOS order is best treated as magical, but usually the disks on built-in sata
interaces go before the disks on add-on cards. For built-in interfaces, the order
may or may not be the same as the labels on the mobo. (if the mobo is labeled correctly
and the bios is in agreement with the labeling).

Then you boot linux and it assigns the names /dev/sda, sdb, etc in the detection order
which is roughly the same as the relevant kernel modules are loaded. The AHCI driver
module is usually loaded first and it probably detects the interfaces in the "lspci" order.
The order of the ports on each interface is again magical. For example, the ASUS A8N-E mobo
with 4 disks on the 4 built-in SATA ports will have this order:
sda=(hd2), sdb=(hd3), sdc=(hd0), sdd=(hd1).

Then you start the SL installer anaconda and it tries to make sense of this. The
result is best described as "we tried for the better, but got the same as ever".

The bottom line is that it the installer cannot "guess" the ordering of the disks
and it cannot "guess" the intent of the user. Instead of "guessing" it should ask.

Instead of asking it brings even more confusion:

For the single disk case, it always guesses right.

For dual mirrored disks (mdadm raid), it says "install bootloader on /dev/sda",
then installs the boot loader on both disks (as it should), but sometimes
it gets the disks cross-referenced - load GRUB from hd0, load vmlinuz and initramfs from hd1.

For three disks (USB installer + dual mirrored disks), it usually installs the boot loader
on the USB disk.

Of 3 common use cases, they get 1 right, 1 almost right and 1 completely wrong.

Then they have a button to select the disk for the boot loader. The offered
menu looks like this: "USB disk, 3TB disk, 3TB disk" - impossible to tell
which 3TB disk is which. (They could should the sda/sdb identification,
the disk serial number, etc).

To improve on this situation, I think the installer should have one more button -
install the bootloader on the same disk where it just installed the OS.

P.S. I do not know if the EFI boot standard makes things any better...


-- 
Konstantin Olchanski
Data Acquisition Systems: The Bytes Must Flow!
Email: olchansk-at-triumf-dot-ca
Snail mail: 4004 Wesbrook Mall, TRIUMF, Vancouver, B.C., V6T 2A3, Canada