[wplug] Linux and XP

Bryan J Smith b.j.smith at ieee.org
Mon Jul 2 11:24:46 EDT 2007


There are also some undocumented sectors in the MBR that NT 5.1 (XP/2003), especially SP2, may write.
These are typically written when the C: drive is greater than 32GiB (33.8GB), or cylinder 4096 (assuming 255/63 heads/sectors) - especially for FAT32.
NT5 (2000+)-based Windows doesn't support creating FAT32 volumes greater than 32GB (for technical reasons), but will use them if pre-existing.
It has to install a hack in the MBR for NTLDR (the 2nd part of the NT bootstrap) which results in this.
Long story short, GRUB can overwrite those sectors and installing XP SP2 can over-write GRUB, resulting in a constant "one works, the other doesn't" scenario.
Just wanted to mention it for those that dual-boot XP - the chance of this happening is why I keep my C: cylinder 1-4096.
Although I haven't seen it when C: is NTFS, and the LDM Disk Label ("Dynamic Disc" partition table) avoids this (although you can't boot GRUB on LDM yet).

The other note is on sda v. hda.  There are some SATA drivers that actually use hda, including Intel AHCI support.
But because of the various issues with libata's support of AHCI, as well as the maturity/lag of various Intel ICH variants, most people don't use it.
I.e., they set "legacy" mode in the BIOS for such Intel chipset systems and it will come up as sda then.

--  
Bryan J Smith - mailto:b.j.smith at ieee.org  
http://thebs413.blogspot.com  
Sent via BlackBerry from T-Mobile  
    

-----Original Message-----
From: Jonathan Billings <billings at negate.org>

Date: Mon, 02 Jul 2007 10:05:46 
To:General user list <wplug at wplug.org>
Subject: Re: [wplug] Linux and XP


Weber, Lawrence A wrote:
> 
> 
> Is there anything special I need to do to install Linux as a second OS 
> on a PC that already has XP?  After several attempts to install a 
> variety of Linux distros, the PC always boots directly to XP.  It looks 
> as if GRUB is not executing.

As part of the install, it should ask you if you want to write to the 
master boot record.  Many distros will automatically detect another OS, 
such as windows, and create the appropriate GRUB entry.

If you don't have this, boot off a rescue CD, and chroot into your 
newly-installed OS's root directory.  Make sure /boot is mounted, if it 
is a separate partition.  Then you can run 'grub-install /dev/sda' (if 
you have a SCSI or SATA disk, it'd be 'grub-install /dev/hda' if you've 
got a PATA or old-style IDE disk).

That'll install on the master boot record of the first disk.

-- 
Jonathan Billings <billings at negate.org>
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