newbie grub to root pratition

[jglen490]

Re: newbie grub to root pratition

Qqmike, as always, is correct in the observation of (hd0) being Grub notation for the MBR of the first bootable device. Grub's code (menu.lst, Stage 1, Stage1.5, etc.) is always loaded to whatever partition has been designated for /boot (quite often included under the / partition, but not always of course). The bootloader code is different and refers to the 512 bytes written (usually) to the MBR of the first bootable device, which must point to where Grub's code is stored so that the BIOS can find it, read it, store it to memory, and execute it. The same applies to Windows' bootloader code, or any other OS bootloader code, and is different from the data stored in a partition's first sector.

[ottosykora]

Re: newbie grub to root pratition

yes, but then when I tried the Xubuntu 8.10, there was dropdown menu connected to the place where otherwise the (hd0) stands.
The grubs nomeclatur is often confusing, so I probably did type it wrong, but the Xubuntu does in its drop down offer /dev/sda9 for my partition. It does not offer hd(0,8) as I assume it should be in the grubs language.

[jglen490]

Re: newbie grub to root pratition

Yes, sometimes it's necessary to translate between how Grub refers to a partition and how Linux referes to the same partition. That's unfortunate, but just part of the open source fun !

Anyway, we all learn from each other everyday.

[Qqmike]

Re: newbie grub to root pratition

In GRUB:
(hdx,y)
is hard drive x,
partition y.
Counting starts at zero.
So, the first hard drive is hd0, the second hard drive is hd1, etc.
The first partition is partition 0, the second partition is partition 1, etc.

Ex.:
(hd1,0) = the first partition of the second hard drive.
(hd0,1) = the second partition of the first hard drive.
(hd3,9) = the tenth partition of the 4th hard drive.

Usually, BUT NOT always,
sda1 = (hd0,0)
sda2 = (hd0,1)
sdb1 = (hd1,0)
sdb2 = (hd1,1)
sdc4 = (hd2,3)


Problems occur when the Linux installer tries to guess the BIOS/GRUB devices (the (hdx,y)'s), but makes the wrong guesses.

The guesses that your Linux system does (try to) make are stored in
/boot/grub/device.map, and they are the devices that the grub shell--an emulator--uses when you use GRUB from the grub shell; thus, things may go wrong that way. Read about it in Section 15 of the GRUB manual. However, if there's a problem, you can always edit device.map and put anything you want in there, even if you are also wrong (along with the Linux OS). adrian15 (Super Grub Disk owner) likes to use the device command to force the right correspondence and so he is always right (by force).

But if you use GRUB from the CLI, using the common and well-known front-end commands, root, setup, quit, geometry, find, etc., you will be OK, always

[ottosykora]

Re: newbie grub to root pratition

yes, the partition naming comes sometimes confused when there is extended partition and many other logical in it. In win we not used to count for that extended one, but here it does count it and so all gets mixed up.