How to install Grub from a live Ubuntu cd.

[Abdus]

Any help on how to make GRUB refresh the list of partitions/systems? I posted this question here, no answer:
http://ubuntuforums.org/showthread.p...75#post7647675

[unutbu]

Abdus, each time you install an Ubuntu distribution and allow it to install grub, it scans your system for operating systems and writes a GRUB menu.lst which lists a boot option for each OS found.

The same would be true of most major Linux distros (Fedora, SUSE, etc).

So if you allow the last Linux distro to install GRUB to the MBR, you should be all set.
GRUB would read the /boot/grub/menu.lst in that last Linux distro's partition and you should see a boot option for each OS on your system.

If you want to regenerate the /boot/grub/menu.lst, then the command you looking for is

sudo update-grub

If you can not boot Ubuntu directly but can boot from a LiveCD, then you can generate the menu.lst by doing the following:

Boot from the Ubuntu LiveCD
Open a terminal (Applications>Accessories>Terminal). Type

sudo mount /dev/sda5 /mnt

Change sda5 to the correct name for your Linux root partition. If you have multiple Linux OSes installed, you must name the Linux root partition that is controlling the boot process. Usually that would be the last OS you installed.

Then type:

cd /mnt
sudo mount --bind {/,}proc
sudo mount  --bind {/,}sys
sudo mount  --bind {/,}dev
sudo chroot /mnt
grep -v rootfs /proc/mounts > /etc/mtab
update-grub

[Abdus]

Abdus, each time you install an Ubuntu distribution and allow it to install grub, it scans your system for operating systems and writes a GRUB menu.lst which lists a boot option for each OS found.

The same would be true of most major Linux distros (Fedora, SUSE, etc).

So if you allow the last Linux distro to install GRUB to the MBR, you should be all set.
GRUB would read the /boot/grub/menu.lst in that last Linux distro's partition and you should see a boot option for each OS on your system.

I understand that, thank you. However it would feel much more safe to have the MBR managed only by one OS, i.e. my Ubuntu Jaunty, which is my main system, and the only one for everyday use. The other systems (windowses, linuxes) are just auxiliary, for testing purposes, and I don't want to let them manage my MBR for more than a few minutes reuired to restore it.

If you want to regenerate the /boot/grub/menu.lst, then the command you looking for is

sudo update-grub

This command did not reread the partitions/systems anew, it just restored the menu as it was before.

If you can not boot Ubuntu directly but can boot from a LiveCD, then you can generate the menu.lst by doing the following: [...]

After installing auxiliary OS's I restore my GRUB using the Ubuntu alternative installation CD, using the menu there ("install GRUB" or similar). This procedure works, however it just restores previous config instead of rereading patitions/systems anew. Would doing what you suggested by the GRUB console reread those?

Thanks for help!

[unutbu]

Ah, I see. I think the Ubuntu installer has some kind of script to detect partitions containing operating systems and then generate the appropriate boot stanzas in menu.lst. I don't know enough about the Ubuntu installer to tell you how to rip out that script so that you may run it independently.

There is no GUI for doing this either, as far as I know.

However, it is not really very hard to edit the menu.lst manually.
While booted into your main Linux OS (Jaunty), mount the last installed Linux distro at, say, /mnt:

sudo mount /dev/sda? /mnt

(again change sda? to the appropriate name).

Then open an editor with root privileges:

gksu gedit /mnt/boot/grub/menu.lst

and open your "controlling" menu.lst. (Click the "Open" button and open /boot/grub/menu.lst.)

Near the bottom of /mnt/boot/grub/menu.lst will be boot stanzas for each of your other operating systems. You can simply copy those stanzas and paste them into Jaunty's menu.lst.

[Abdus]

That is an excellent tip, unutbu, thank you for it, I'll try it with no doubt! Are you sure that partitions UUIDs are same in both the linuxes on my machine though?

PS. I still find it unbelieevable that so well established and already old app as GRUB has no "rread" option. Amazing, isn't it?

[Frynz Frostblade]

this is it. thank you. u rock!!!

[chanklor]

chanklor, GRUB reads files in your ubuntu partition (such as /boot/grub/menu.lst and stage2) during the boot process. Since you've removed the ubuntu partition, GRUB is no longer viable.

To regain the ability to boot Vista, you'll need to restore the default Vista MBR (master boot record). Here are instructions on how to do that:

http://ubuntuforums.org/showthread.php?t=740221

thanks a lot! exactly what i needed
thansk thanks thanks!

[izint]

:/ anyone know how to fix my problem? frmo the previous page

[kuppalli]

This worked with me.
Thanks a lot.

Please try the chroot grub-install and post what happens. Like I said I saw the how to when I didn't understand commands and never saw it again. Then I saw the grub manual describing the find, root, setup commands and I went with that.I think find, root, setup doesn't return the bios error because they are given from the grub shell.
Just for FYI, this is the error I get with grub-install from the live session.

ubuntu@ubuntu:~$ sudo grub-install /dev/hda
Probing devices to guess BIOS drives. This may take a long time.
Could not find device for /boot: Not found or not a block device.

This is the output of find, root, setup

grub> find /boot/grub/stage1
 (hd0,1)
 (hd0,10)

grub> root (hd0,10)
 Filesystem type is ext2fs, partition type 0x83

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)"... failed (this is not fatal)
 Running "embed /boot/grub/e2fs_stage1_5 (hd0,10)"... failed (this is not fatal
)
 Running "install /boot/grub/stage1 d (hd0) /boot/grub/stage2 p /boot/grub/menu
.lst "... succeeded
Done.

[Vesperatus]

July 27,

A vista update seems to have eaten part of my grub. Anyway, with this post and the help of others, I got it working again.

If the original submitter still reads, adding how to find the (hdx,y) would help. The "find /boot/grub/stage1" is not working on my installation. I had to do : find "/grub/stage1" . Searching for /boot/grub/stage1 resulted in an Error 15 : File not found.

I suppose any combination of
/boot/stage1
/boot/grub/stage1
/grub/stage1
/stage1

might return something.