Re: black screen / blinking cursor after grub-install

[Felix Miata]

On 2011/08/11 16:11 (GMT-0600) J.V. composed:

> >  J.V. wrote:

> > >  I have a black screen with a single blinking cursor after running:
> > >      #grub-install /dev/sda1

> I tried to do that just now, and it did not work.  I am looking for
> additional solutions to make my system boot and undo what #grub-install
> /dev/sda1 did

> ---
> I tried using the CentOS 6 media in rescue mode to do this and got this
> error
> #grub-install /dev/sda

> /sbin/grub: Not found.
> sh-3.2#

Rescue mode is a limited environment. Grub-install is a shell script that 
depends on an adequate environment, part of which is the target location 
being mounted to /boot, part of which includes a proper /boot/grub/device.map 
file, and absence of which requires extra parameters on its cmdline for it to 
work. I find it much easier to ignore the existence of grub-install and use 
the Grub shell to execute as little as two commands to install Grub.

find /boot/grub/stage1 #only necessary if you are not sure of the ID of the 
target
root (hd0,0) # sets up partition containing files for Grub shell to work with
setup (hd0,0) # installs grub on the first partition on the first HD

The simplicity of the above can fail if more than one HD is in the system and 
a correct device.map file cannot be found by the Grub shell in /boot/grub in 
the specified root partition.

The easiest way to get grub-install to work correctly includes mounting the 
target on /boot, which a rescue boot will not do automatically.

> =>  so that is not possible with the CentOS 6 boot cd in rescue mode.

> I then cut a knoppix CD and did the same thing and got

> grub-probe: error: cannot finda  device for / (is /dev mounted?).
> grub-probe: error: cannot find a device for /boot/ (is /dev mounted?).
> Could not find device for /boot: Not found or not a block device.

> so my system will not still not boot after completing the advice given.

Booting Knoppix is just another form of rescue boot. Grub-install won't find 
_your_ /boot directory or device.map file before you mount the correct 
partition to its /boot directory, or supply appropriate extra command line 
parameters to it.

The Grub shell commands I gave above will work (I do them as often as I 
install brand new HDs that I don't clone from an old HD), assuming (hd0,0) 
aka /dev/sda1 is the appropriate target, but may require disconnecting the 
other 2 HDs until your problem gets figured out. Also assumed is the standard 
MBR code from the Windows installation remains on the MBR, and the Grub 
target partition has its boot flag set, and no other primary partition on the 
1st HD has a boot flag set.
--
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 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata  ***  http://fm.no-ip.com/