How to install Grub from a live Ubuntu cd.

[linfidel]

ugh...

any ideas? will i have to reinstall this damn liveCD AGAIN???

No, you never need to reinstall the live CD. But, you should understand what's going on, and maybe that will be harder, although it's really not very complicated, at least it wasn't until the latest version, if you did a clean install and ended up with "GRUB 2". Installing GRUB (1) is easy, but if you have GRUB 2, I don't know how. In fact, I simply installed the original GRUB manually.

For GRUB 1, you need two things - you need the grub files in /boot/grub, along with menu.lst, and you need the boot loader in the MBR that knows where to look for the OS and the grub files.

If you have an existing /boot/grub/ then using the live CD to fix things is easy - all you have to do is tell GRUB where they are, and reinstall it into the MBR. This takes two commands from the grub prompt.

You need to know what partition your root linux is on. If you only have one, it would be /dev/sda1 (first drive, first partition). But in GRUB's terminology, this is HD0,0 (no spaces).

For me, my root drive is an extended partition, which always starts with 5, so it's /dev/sda6, the first logical partition in the extended partition.

Here's what I do to install GRUB from the live CD (pre-9.1 version):
Enter "sudo grub" in the terminal. Always use sudo (or an su prompt) or grub will run, but not work worth a damn!

grub> find /boot/grub/menu.lst
 (hd0,5)

grub> root (hd0,5)

grub> setup (hd0)
 Checking if "/boot/grub/stage1" exists... yes
 Checking if "/boot/grub/stage2" exists... yes
 Checking if "/boot/grub/e2fs_stage1_5" exists... yes
 Running "embed /boot/grub/e2fs_stage1_5 (hd0)"...  16 sectors are embedded.
succeeded
 Running "install /boot/grub/stage1 (hd0) (hd0)1+16 p (hd0,5)/boot/grub/stage2 /boot/grub/menu.lst"... succeeded
Done.

grub> quit

Explanation. First, I did a find to confirm the location of my grub files, using menu.lst (because I can remember that one easily).

The GRUB prompt is "grub>", by the way.

Then, I told GRUB about that location, with the "root" command, installed the boot loader into the MBR with the setup command, saw that everything was OK, and entered "quit" to exit.

That's what does it for me.

[brtaylor92]

To throw in my experience with fixing grub2 after an incident with Windows overwrote the MBR:

Follow the chroot instructions at the beginning of this thread - mount your install partitions, and so forth.

from the chrooted environment:

sudo apt-get install grub
sudo apt-get install grub2
sudo upgrade-from-grub-legacy

At this point, whether you have a legacy grub install or not (I didn't), grub seems to simply bring up the upgrade screen - which will prompt you for which drive to install grub2 on if it doesn't find a legacy install. It then automatically regenerates your /boot/grub/grub.cfg file (which contains menu entries similar to those in menu.lst for the original grub). It didn't detect my Windows install, but that can't be considered a reliable indicator as my Windows install currently doesn't boot. Adding Windows to grub.cfg is fairly simple - simply add the lines (for example)

### BEGIN /etc/grub.d/30_os-prober ###
menuentry "Microsoft Windows XP Home Edition (on /dev/sda1)" {
        set root=(hd0,1)
        chainloader +1
}
### END /etc/grub.d/30_os-prober ###

For a Windows XP install on /dev/sda1, for example.
Finally, a sudo grub-install, and a reboot.

More complicated than the old way, and there are probably some unnecessary/erroneous steps involved since I did this off the top of my head, but it works (at least for me).

[lnappa]

https://wiki.ubuntu.com/Grub2#Recover Grub 2 via LiveCD

[swamy2712]

grub> find /boot/grub/grub.cfg
(hd0,7)

grub> root (hd0,7)

grub> setup (hd0)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... no

Error 15: File not found

please help me how to fix this problem

[von Stalhein]

grub> find /boot/grub/grub.cfg
(hd0,7)

grub> root (hd0,7)

grub> setup (hd0)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... no

Error 15: File not found

please help me how to fix this problem

Some more details please:

Which version of Ubuntu?
Is it GRUB 1.97? (looks like it - which one do you want to install?)
Do you only have one hdd?
Are you dual booting?

Stick with it, you're only just beginning to have fun

[OzRattler]

Thanks for the edits at the top of this long thread! Much appreciated. Silly me, forgot that the disk might not have been mounted.

Gods of Linux indeed...............

Have fun!

EDIT:::
I had to edit the syntax at the loader because for some reason it had chosen (hd0,2) instead of (hd0,5) - coincidental that I had the same setup as the OP's edit. Got into 10.04 and from there changed <menu.lst>. That killed XP. So, back into <menu.lst> and see what was wrong. It was still looking for the old drive! Removed the "map" lines and back in action. R.
:::END

[Timmer1240]

Im gonna print this for future reference thanks!

[kannadiga]

This procedure worked for me hope this works to you..

find the "sda (number)" where you have installed ubuntu (previously installed).

To find it goto System -> Admin -> gparted (only using live-cd)
here you find the sda (number) for linux ex: sda7 or sda4 .....

Assuming you were previousely installed ubuntu in sda5

in command prompt type ( Application ->accessories->terminal)

sudo mkdir /media/sda5
sudo mount /dev/sda5 /media/sda5

sudo grub-install --root-directory=/media/sda5 /dev/sda


it shows installation finished. No error reported.

reboot the system.

[swiftwood]

Well my Grub is definitely busted

I tried all the tips here, no go

Given the amount of errors I was getting while backing up my files,
I think my harddrive is on the fritz.

[linfidel]

Well my Grub is definitely busted

I tried all the tips here, no go

Given the amount of errors I was getting while backing up my files,
I think my harddrive is on the fritz.

Was there some reason you posted this? I didn't see a request for help, nor did I see any kind of added information, unless I'm unaware that everyone else has been waiting to hear the status of your hard drive.