Mailinglist Archive: opensuse (1523 mails)

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Re: [opensuse] Confused by hard drive naming/position /dev/sda vs hd0 etc,
  • From: Felix Miata <mrmazda@xxxxxxxxxxxxx>
  • Date: Fri, 12 Mar 2010 15:36:39 -0500
  • Message-id: <4B9AA5D7.8060206@xxxxxxxxxxxxx>
On 2010/03/12 19:25 (GMT+0100) C composed:

Does anyone have any hints or clues for me here?

You have a complex configuration. Few answers will be simple. I certainly
don't have them all, but hopefully here's some help:

*buntu 9.10 uses Grub 2. No version of openSUSE uses that yet, although it is
an option in Factory. Grub 2 (actually 1.9x) is more complex, and possesses
some significant differences from Grub 1 used by openSUSE.

hd3 has different meanings to the kernel, to Grub 1, and to Grub 2. What hd3
means to Grub 1 depends on the content of /boot/grub/ Grub 1
counts from 0, while Grub 2 counts from 1. More differences than that I won't
get into. Grub 1 is good enough for me that I haven't yet been compelled to
learn Grub 2.

A modern PC BIOS has several settings options that affect which HD gets
priority. Commonly there's one to assign two SATA ports to a separate group
from four other SATA ports, and an ability to switch the priority between the
two groups, as in earlier BIOS with both SATA and PATA support. Also whether
AHCI, by whatever name the BIOS assigns it, is enabled, affects which devices
can have priority, priority which won't necessarily agree with what either
Grub or the kernel thinks. On top of those and any other normal BIOS
settings, most have a boot time menu option to boot from, which IOW means
assign top priority regardless of other settings. The results possible from
this matrix for any particular BIOS can only be learned through trial and
error. In your case of using so many devices, you probably need to spend some
time experimenting and documenting the possibilities.

The foregoing is why device names for boot and mount purposes have had to be
deprecated, replaced by UUID, label, path and ID as optional ways around the
problems of unstable and unpredictable device priority.

I suggest attempting to master either or both Grubs, create a boot partition
as host for one Grub and a master Grub menu, but once initially configured,
never mount that personal boot partition as /boot. It'll be up to you to
maintain it with configfile and/or chainloader stanzas for your various
distros, and if you want, graft in stanzas from your various distros' boot
menus. Each distro in turn should have its own Grub installed to its / (or to
a separate /boot dedicated to use exclusively by that installation if you want).

Once you have Grub configured suitably, there should be no reason either to
change BIOS settings, or use the BIOS boot menu. Each distro can be allowed
to do whatever it pleases with whatever interpretation of BIOS priorities it
perceives, and boot and mount by UUID, device name, or whatever it deems
best. The main thing you need to do with each is ensure it does nothing with
any HD's MBR, or with _your_ special Grub host/boot partition. If you don't,
each will assume it's job is to hijack everything related to booting
anything, and your's is far too complex to let that can of worms be opened.

FWIW, I mount both realboot and non-booted distros' / partitions in a tree
called /disks, in subdirs named ./hd[1-x]/, to directories with descriptive
names, such as boot, suse112, fedora12, mdv2010, kubuntu, etc. I also label
each partition, usually the same as the dirs used in /disks/hd[1-x]/, and use
the labels for manual mounting & unmounting, and fstab entries. UUIDs were
not made for human manipulation. :-p I also do all partitioning and
formatting prior to beginning any Linux installation, and only _use_
"existing" partitions from within any distro's installation program.

There's yet another option that can be used instead of a personally
maintained custom boot partition - use Windows as primary bootloader. A basic
HOWTO is on but I don't recommend
using that method on so complex a system as yours unless you actually install
Windows to a logical and keep only its boot files on its C: primary.
Otherwise, Windows could turn your ability to boot anything else into a mess
you wouldn't want to think about. ;-) The nice thing about this method though
is configuration menu access is available from anything you can get to boot,
including a 25 year old DOS floppy disk (as long as C: is the first partition
on the first BIOS HD). :-)
"The wise are known for their understanding, and pleasant
words are persuasive." Proverbs 16:21 (New Living Translation)

Team OS/2 ** Reg. Linux User #211409

Felix Miata ***
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