GRUB menu not getting updated even after changing /boot/grub/grub.cfg

KNSI · 06-19-2018, 08:48 AM

Hi,

i have completed compiling Linux From Scratch 8.1 on Ubuntu-16.04(minimal).
while setting up GRUB i have set the root to the wrong partition, the grub.cfg file is shown below:

Code:

set default=0
set timeout=5
insmod ext2
set root=(hd1,0)
menuentry "GNU/Linux, Linux 4.12.7-lfs-8.1" {
        linux   /boot/vmlinuz-4.12.7-lfs-8.1 root=/dev/sdb1 ro
}

plus i had run

Code:

grub-install /dev/sda

hence GRUB had shown the following error:

Code:

error: no such partition

so i clicked on 'c' and set the root to (hd1,1) and the OS booted. After which i updated the grub.cfg file to:

Code:

set default=0
set timeout=5
insmod ext2
set root=(hd1,1)
menuentry "GNU/Linux, Linux 4.12.7-lfs-8.1" {
        linux   /boot/vmlinuz-4.12.7-lfs-8.1 root=/dev/sdb1 ro
}

and again rebooted to check the configuration, but it seems as though the change is not getting reflected as it still gives me the same error and i have to once again set the root to (hd1,1).

so my question is how do you permanently update the grub? i have also tried

Code:

grub-install /sda/sdb

but it seems to not make a difference.

yancek · 06-19-2018, 10:32 AM

Are the entries in grub.cfg you refer to on the Ubunt system or on the LFS?
Your output shows LFS on sdb1 so I would think you would want to install Grub to that drive: grub-install /dev/sdb (as root or using sudo).

I haven't used LFS but I see on their site they have a 'live' option. Post a link to what you used. If you are creating a 'live' system you won't be able to edit the grub.cfg file and save the changes on reboot. You should be able to put an entry in the grub.cfg file of Ubuntu and boot it any time.

KNSI · 06-19-2018, 11:30 AM

Quote:

Originally Posted by yancek

Are the entries in grub.cfg you refer to on the Ubunt system or on the LFS?
Your output shows LFS on sdb1 so I would think you would want to install Grub to that drive: grub-install /dev/sdb (as root or using sudo).

I haven't used LFS but I see on their site they have a 'live' option. Post a link to what you used. If you are creating a 'live' system you won't be able to edit the grub.cfg file and save the changes on reboot. You should be able to put an entry in the grub.cfg file of Ubuntu and boot it any time.

Hi,

It is the grub.cfg of the LFS system.
i did run grub-install /dev/sdb as the sudo user, but when i run fdisk -l, it still shows /dev/sda as the boot partition.
I also tried running the grub-install command in the chroot environment as instructed in http://www.linuxfromscratch.org/lfs/...sedchroot.html.

i built the GRUB configuration as instructed in http://www.linuxfromscratch.org/lfs/...er08/grub.html.

yancek · 06-19-2018, 04:43 PM

If the device on which you have created LFS is sdb and you installed Grub to the MBR of sdb, it should boot if you have sdb set to first boot priority in the BIOS. The only reason the changes aren't save that is logical is that it is a live system, therefore read-only and no changes are saved on reboot. Haven't used LFS so I doubt I'll be much help.

AwesomeMachine · 06-19-2018, 06:37 PM

Manual changes to grub.cfg are lost when reinstalling or updating grub. Grub.cfg is built using the scripts in /etc/grub.d.

colorpurple21859 · 06-19-2018, 07:16 PM

Is this an efi system with an esp/efi partition formatted fat32?

rtmistler · 06-20-2018, 01:54 PM

Please post your thread in only one forum. Posting a single thread in the most relevant forum will make it easier for members to help you and will keep the discussion in one place. This thread is being closed because it is a duplicate.

Please use your original question on this topic, https://www.linuxquestions.org/quest...fg-4175632183/