[gentoo-dev] question about grub

[gentoo-dev] question about grub

[Ryan McLean]

Hello,

  I was reading your excellent installation documentation online, and I
ran into a question.  Near the end you're breaking down the commands for
grub, but you leave some information out that I would like to know:

# Below needed only for people who dual-boot
title=Windows NT Workstation
root (hd0,5)
chainloader +1

  I'm unclear as to what the (hd0,5) are pointing to, is to say "boot of
off the FAT partition located at partition 5"?  Normally MS likes to
reside on the primary partition of the drive, so I just want clarification
on this.  For instance, if I have a dual boot, MS on the primary partition
and Gentoo's root at (sd0,3), then I would put root (sd0,1) under my
Windows boot section, correct?  And also, what does the chainloader +1
command do?  Thank you fo your time, I'm an old fan of lilo, but I have
been cosidering migrating to a newer bootloader :)

 - Ryan

/*
 * Ryan McLean - Network/System Administrator
 * Starshadow Communications
 * Chicago, Illinois USA
 * http://www.starshadow.com
 */

Re: [gentoo-dev] question about grub

[Matthew T. Jachimstal]

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On Fri, 2002-03-15 at 13:00, Ryan McLean wrote:
> Hello,
> 
>   I was reading your excellent installation documentation online, and I
> ran into a question.  Near the end you're breaking down the commands for
> grub, but you leave some information out that I would like to know:
> 
> # Below needed only for people who dual-boot
> title=Windows NT Workstation
> root (hd0,5)
> chainloader +1
> 
>   I'm unclear as to what the (hd0,5) are pointing to, is to say "boot of
> off the FAT partition located at partition 5"?  Normally MS likes to
> reside on the primary partition of the drive, so I just want clarification
> on this.  For instance, if I have a dual boot, MS on the primary partition
> and Gentoo's root at (sd0,3), then I would put root (sd0,1) under my
> Windows boot section, correct?  And also, what does the chainloader +1
> command do?  Thank you fo your time, I'm an old fan of lilo, but I have
> been cosidering migrating to a newer bootloader :)

I'll take a quick stab at this:

First, always add 1 to grub's numbers for disk and partition. The first
partition of the first disk is (hd0,0). So, if your Windows is on sda1,
the grub parameter is (sd0,0).

The chainloader +1 (I think) means to start chain loading the boot
loader 1 sector from the start of the specified (root) partition.

There's some excellent grub docs at the GNU website:
http://www.gnu.org/manual/grub-0.90/grub.html

I'd definitely encourage you to move to grub. Writing the boot sector
once really is much nicer. I messed up a config file, putting hd(0,0)
instead of (hd0,0). With LILO I would've needed to find a boot disc. In
grub, I simply edited the boot commands from the menu and merrily went
on with the boot.

Have fun!
Matthew

-- 
       Matthew T. Jachimstal        | Phone:  (419) 861-3331   .~.
       System Administrator         | FAX:  (419) 861-3340     /V\
        Unique Systems, Inc.        | http://www.uniqsys.com  // \\
6920 Spring Valley Drive, Suite 106 | matthew@uniqsys.com    /(   )\
         Holland, OH 43528          |                         ^`~'^

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Re: [gentoo-dev] question about grub

[Dan Armak]

On Friday 15 March 2002 20:00, Ryan McLean wrote:
> Hello,
>
>   I was reading your excellent installation documentation online, and I
> ran into a question.  Near the end you're breaking down the commands for
> grub, but you leave some information out that I would like to know:
>
> # Below needed only for people who dual-boot
> title=Windows NT Workstation
> root (hd0,5)
> chainloader +1
>
>   I'm unclear as to what the (hd0,5) are pointing to, is to say "boot of
> off the FAT partition located at partition 5"?  Normally MS likes to
> reside on the primary partition of the drive, so I just want clarification
> on this.  For instance, if I have a dual boot, MS on the primary partition
> and Gentoo's root at (sd0,3), then I would put root (sd0,1) under my
> Windows boot section, correct?  And also, what does the chainloader +1
> command do?  Thank you fo your time, I'm an old fan of lilo, but I have
> been cosidering migrating to a newer bootloader :)
One thing you must be careful with is the partition numbers. In grub, unlike 
the /dev/hdxy devices, the first partition is numbered 0 not 1. So (hd0,5) is 
first harddisk, sixth partition.

chainloader +1 boots a partition that has custom boot code in its boot sector. 
In our case, the windows boot code. Without it grub would mount the partition 
and load a linux-style kernel (with a kernel= line).

-- 
Dan Armak
Gentoo Linux Developer, Desktop Team (KDE)
Matan, Israel