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Re: howto grub-install

From: Felix Miata
Subject: Re: howto grub-install
Date: Tue, 09 Aug 2011 17:30:37 -0400
User-agent: Mozilla/5.0 (OS/2; Warp 4.5; rv:6.0) Gecko/20110731 SeaMonkey/2.3

On 2011/08/09 13:58 (GMT-0600) J.V. composed:

I have installed CentOS 6.0 on a SATA drive, default settings.
Default settings can be a big problem in a multiboot environment. I've not
used any CentOS, so have no idea what they may be there.

I was reading the grub manual and it led me to do the following:
At the root command prompt, I typed:
      #grub-install /dev/sda1
now when I boot, I have a black screen with a single blinking white cursor
IIRC that's because boot failed and your PC BIOS is too stupid to provide an
error message to that effect.

Question 1)
      What went wrong?

Grub installation failed. Maybe /boot/grub/ was missing or
incorrect? Grub-install is a script that depends on configuration done in
advance, which normally the OS installer gets right, but not always.

Did you install while only one HD was in the system, then change to more than
one, or vice versa? Doing either buys a lot of grief, unless you're
experienced in multiboot and boot loaders.

Question 2)
      How do I get my OS back?

CentOS, or Windows?

For CentOS, first, boot something that can tell you whether any partition has
been set active. As long as standard MBR code is used, normally the best
choice when Windows is installed, one and only one primary partition on the
first disk must be marked active. A DOS boot floppy can do this if FDISK is
on it. Any of fdisk, cfdisk, sfdisk, parted, etc can do this from any Linux 

Boot the CentOS installation media and try again to install Grub. If you
can't manage that, you may need to install Grub manually from a CentOS rescue
boot, or from a Knoppix live CD/DVD.

On a new system with no installed operating systems I usually partition
first, then mkfs (usually EXT2) on a primary partition that will provide a
home for a Grub (not necessarily the one the OS being installed thinks you'll
be using, or will install), then "install" Grub manually using the Grub shell
and copying the required files from the Knoppix media to /boot/grub/ on
Grub's partition.
shows generally how I do it typically using only 4 commands, then rebooting.

I have Windows 7 installed on the second SATA drive, how do I show this
in the grub boot menu?
I read the manual section about "chainloader" and another section
referring to "menuentry", but the instructions were not specific enough
for use.
Question 3)
      What file do I edit to make "chainloader" go?  I understand the
concept, so now what?


You don't actually need a menu to get booted, so focus first on just getting
into Grub, be it menu or shell. The menu consist merely of commands stanzas
you can run manually from the Grub shell.

Question 4)
      Where/what file does "menuentry" go in?

Menuentry is for Grub 2. CentOS 6 uses Legacy Grub (Grub 1).
if it still exists may have most answers you need.
is pretty useful too.
"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 ** a11y rocks!

Felix Miata  ***

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