[CentOS] Re: Installation problem, possibly RAID

Bryan J. Smith b.j.smith at ieee.org
Sun Sep 11 17:17:08 UTC 2005

On Sun, 2005-09-11 at 11:41 -0500, Les Mikesell wrote:
> I thought you could specify root=LABEL=xxx in the grub kernel line.  I
> usually avoid labels when making custom changes because the stock
> labels aren't unique and the system cannot deal with duplicates
> if you ever move a disk to a different machine but it should work
> if you just shift them around in the same box.

Yes and no.

Yes, it's more capable than NTLDR on a legacy PC BIOS/DOS disk label.

But no, it doesn't solve the BIOS disk order to Linux device name
mapping issue.  You _still_ have to tell GRUB how to map BIOS fixed
disks (80h, 81h, 82h, etc..., what GRUB calls hd0, hd1, hd2, etc...) to
Linux devices (hda, hde, sda, etc...).

> It might be better to use LVM identifiers which are probably unique
> if you don't do full disk image copies to clone machines. 

NT's LDM and Linux's LVM drastically help the bootstrap location issue.
Unfortunately, there are still assumptions/issues of the PC BIOS Int13h
Disk Services to contend with at boot (that aren't issues on other
platforms).  The disk label will never solve this until we use a non-
legacy boot approach.

In all honesty, with Intel and Phoenix sleeping together, and
Microsoft's wish (and their "superstore vendor" whores) to tie the PC
firmware to specific Windows releases, there's virtually _no_movement_
on this.  Which brings me to Apple -- I think they will "raise the bar"
on the PC platform with their proprietary approach.  From that, AMD and
the various Tawainese/Chinese manufacturers will come up with a clone
that is an open standard, and will be universally adopted.

That's my prediction in the next 3-4 years.  Just like PXE finally
brought UNIX workstation-like booting to the PC world, I think Apple's
innovations on the PC platform (even if proprietary) will encourage
vendors to clone it with an open implementation.

> It's slightly better than in the years when PC disks had a 32 meg
> maximum size, but not much.  Even more recently the 1024 cylinder
> limit has been in bios for so long that I just always put a /boot
> partition first on the first drive automatically even if it is
> not always necessary these days.  

As far as I'm concerned, _unless_ you are using a LDM Disk Label (aka
"dynamic disk"), there is a real 33.8GB (32GiB) limit on the C:
filesystem when dual-booting with Windows XP SP2+.

Bryan J. Smith     b.j.smith at ieee.org     http://thebs413.blogspot.com
The best things in life are NOT free - which is why life is easiest if
you save all the bills until you can share them with the perfect woman

More information about the CentOS mailing list