[SOLVED] grub prompt at boot

xstorae · 01-10-2012, 08:43 PM

I got a new laptop today, with Windows 7 pre-installed. I've been working for most of the day to dual boot it with Ubuntu, and had a bit of trouble installing GRUB. Eventually, I *think* I got it to install on the partition Ubuntu is on - at least that is what I wanted. But now when when I boot up the computer, it gives me a Grub prompt (after a short intro saying something about how the tab can complete your commands), and I'm at a loss for what to do with it.

To make matters worse, none of the normal grub commands seem to work; it cannot find root or kernel commands, help returns a list of things, help root doesn't return anything, help kernel likewise, and only 'exit' actually seems to work, which just restarts the boot..going back to grub again.

Have I not installed grub correctly? Should I go back to Ubuntu livecd desktop and try something else? Or is it a problem with my recently made partitions?
Thanks for any advice you can offer!

TroN-0074 · 01-10-2012, 09:01 PM

Put the CD back in the computer and boot from it, make sure internet connection is working, open up a terminal and type the following commands (This fix is not going to work if you installed Ubuntu using the WUBI installer pre pack in the disk)

paste this code in terminal

Code:

sudo mkdir /media/root

press enter then paste this other code

Code:

sudo mount /dev/sda1 /media/root

press enter and paste this other code

Code:

sudo grub-install --root-directory=/media/root dev/sda

press enter and that should do

reboot, remove the disk from the tray a post back here how you did with the new OS.

Larry Webb · 01-10-2012, 09:43 PM

Quote:

Originally Posted by TroN-0074

press enter then paste this other code

Code:

sudo mount /dev/sda1 /media/root

reboot, remove the disk from the tray a post back here how you did with the new OS.

Why would he want to mount sda1 when he is dual booting windows?

Here is a good tutorial on grub2

Pay attention to Section 12

TroN-0074 · 01-10-2012, 10:33 PM

To see what partition your ubuntu linux is intalled copy this code in terminal

Code:

sudo fdisk -l

press enter. you will see something like

Code:

Disk /dev/hda: 120.0 GB, 120034123776 bytes
255 heads, 63 sectors/track, 14593 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes


Device    Boot               Start                 End                Blocks      Id          System
/dev/sda1                      1                  1224                 64228+     83          Linux
/dev/sda2  *                 1225                 2440                9767520     a5          Windows
/dev/sda3                    2441                14593               97618972+     5          Extended
/dev/sda4                   14532                14593                498015      82        Linuxswap

See in this example you can see the linux partition is actually called sda1 which will be fine with the suggestion in post#2

in your case it might be calle different. Issue the sudo fdisk -l command and check the name of your partition

then you can proceed with the steps in post #2 mounting the right partition.

Good luck

xstorae · 01-10-2012, 11:19 PM

Thank you, mkdir and mount went fine, but when I entered:

sudo grub-install --root-directory=/media/root dev/sda

it returned:

/usr/sbin/grub-probe: error: cannot stat `dev/sda'.

When making the partitions, every guide I found said to make multiple partitions for ubuntu - for /boot, root, and home. I chose the one I'm pretty sure was for boot for mounting. Was that not the right choice?
Thanks for the help

deep27ak · 01-11-2012, 12:05 AM

Quote:

Originally Posted by xstorae

I got a new laptop today, with Windows 7 pre-installed. I've been working for most of the day to dual boot it with Ubuntu, and had a bit of trouble installing GRUB. Eventually, I *think* I got it to install on the partition Ubuntu is on - at least that is what I wanted. But now when when I boot up the computer, it gives me a Grub prompt (after a short intro saying something about how the tab can complete your commands), and I'm at a loss for what to do with it.

To make matters worse, none of the normal grub commands seem to work; it cannot find root or kernel commands, help returns a list of things, help root doesn't return anything, help kernel likewise, and only 'exit' actually seems to work, which just restarts the boot..going back to grub again.

Have I not installed grub correctly? Should I go back to Ubuntu livecd desktop and try something else? Or is it a problem with my recently made partitions?
Thanks for any advice you can offer!

can you attach a snapshot of the place where your grub gets stucked?
are you able to go to single user mode?
can you post your grub.conf file?

and as the last command you tried as per me it should be

Code:

grub-install --boot-directory=/media/root dev/sda1

through this command you are trying to create a boot directoy and installing grub in /dev/sda1

xstorae · 01-11-2012, 12:58 AM

@Larry Webb I followed the guide you pointed to on reinstalling Grub2, and it seemed to work. I rebooted, and got the grub prompt again (this is normal? it seems weird, but maybe it's just until things are configured correctly?) Now it seems that root is semi-working; when i type

grub> root (hd0,

and then press tab instead of enter, i get a list of partitions to choose from (which was definitely NOT happening before re-installation). But whichever number I choose, after pressing enter grub returns:

error: unknown command 'root'.

So I'm at a loss with what to do now

Thanks for all the responses.

Larry Webb · 01-11-2012, 05:28 AM

Sounds like the mbr can not find the / partition.

Download and run Boot Info Script program using your ubuntu disk as a live cd and post the results. This will give us all the information we should need and not be guessing.

Boot Info Script

xstorae · 01-11-2012, 10:20 AM

Thanks Larry, I didn't know this existed. Here it is...

http://paste.ubuntu.com/800713/

Larry Webb · 01-11-2012, 11:08 AM

Using your live cd go to terminal and enter following commands

sudo mkdir /mnt/sda7 (enter)

sudo mount /dev/sda7 /mnt/sda7 (enter)

sudo grub-install --root-directory=/mnt/sda7 /dev/sda (enter)

reboot h/d

xstorae · 01-11-2012, 11:23 AM

Thanks Larry, I did that and grub loaded when I rebooted without the livecd, and did the same thing I was describing earlier when I entered root(hd0,x). Am I even supposed to be seeing grub show up when I reboot like this?

xstorae · 01-11-2012, 11:29 AM

And the info script after doing that is here:

http://paste.ubuntu.com/800806/

Larry Webb · 01-11-2012, 12:13 PM

Sorry I missed the boot info, substitute 5 for the 7 in post #10 commands

xstorae · 01-11-2012, 12:22 PM

Yeah, that's what I did originally actually. I just did it again and the same thing occurs.

grub> root(hd0,x)
error: unknown command 'root'.

JimBrewster · 01-11-2012, 12:47 PM

If you're trying to use legacy grub commands, they are almost completely different in grub2.