[SOLVED] My LFS system won't boot up after accidentally setting grub to hd1 instead of hd0

George528 · 05-17-2021, 11:31 AM

I just finished my LFS build but after rebooting i see this:

https://i.imgur.com/8boZJxL.png

https://i.imgur.com/QqMKlec.png

then I remembered that when configuring grub.cfg file i put
set root=(hd1,6) instead of set root=(hd0,6).

also i have to point out that when i booted up from my live cd, the /boot directory was empty

https://i.imgur.com/4WO3KZP.png

and all partitions where unmounted , only the host partition ans swap was mounted.

how do i change fix this? do i have to enter chroot enviroment from live cd to install grub again?

hendrickxm · 05-17-2021, 12:31 PM

Yes, just chroot and change what is wrong.

hazel · 05-17-2021, 12:36 PM

I don't think you need to chroot. Just mount the LFS root partition somewhere convenient and edit grub.cfg by hand. You aren't reinstalling grub, after all, just changing the location information you give grub once it's loaded.

btw if you boot from a live disc, the /boot partition you see will be the one on the disc, so it may well be empty. To see the boot partition on your hard drive, you need to mount your root (say on /mnt) and then look at /mnt/boot.

George528 · 05-17-2021, 12:36 PM

Quote:

Originally Posted by hendrickxm

Yes, just chroot and change what is wrong.

ok i will chroot, but can you explain why my /boot directory in LFS hierarchy is empty? i am sure i installed installed grub in /boot (/boot is a separate directory)

hendrickxm · 05-17-2021, 01:04 PM

You install grub as a piece of software but you install grub as bootloader as well. Those are two different things.
If you boot and see a grub command, the bootloader part is done but you messed up the config.
You can change the config without chroot but you would need to mount the LFS-partition and edit the grub config file.

themightydill · 05-17-2021, 01:49 PM

Well.
Press E in GRUB and edit (hd1) to (hd0)??

George528 · 05-17-2021, 01:50 PM

Quote:

Originally Posted by hazel

I don't think you need to chroot. Just mount the LFS root partition somewhere convenient and edit grub.cfg by hand. You aren't reinstalling grub, after all, just changing the location information you give grub once it's loaded.

btw if you boot from a live disc, the /boot partition you see will be the one on the disc, so it may well be empty. To see the boot partition on your hard drive, you need to mount your root (say on /mnt) and then look at /mnt/boot.

I mounted /boot on /mnt/boot, but its still empty, i can't find my config file there

was i supposed to move/copy the linux kernel dir in /boot? i did't do it

colorpurple21859 · 05-17-2021, 02:01 PM

Quote:

I mounted /boot on /mnt/boot

what command did you run to mount /boot on /mnt/boot? Do you have a separate boot partition? Post the output of

Code:

parted -l

George528 · 05-17-2021, 02:06 PM

Quote:

Originally Posted by colorpurple21859

what command did you run to mount /boot on /mnt/boot? Do you have a separate boot partition? Post the output of

Code:

parted -l

i used the command

Code:

mount /dev/sdb9 /mnt/boot

yes /boot is a separate partition

here is the output

Code:

root@ubuntu:/# parted -l
Model: ATA Patriot Burst (scsi)
Disk /dev/sdb: 240GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:

Number  Start   End     Size    Type      File system     Flags
 1      1049kB  10.2GB  10.2GB  primary   ext4            boot
 2      10.2GB  240GB   230GB   extended
 5      10.2GB  134GB   124GB   logical   ext4
 6      134GB   220GB   85.9GB  logical   ext4
 7      220GB   225GB   5368MB  logical   ext4
 8      225GB   230GB   5368MB  logical   ext4
 9      230GB   231GB   1074MB  logical   ext4
10      231GB   240GB   8590MB  logical   linux-swap(v1)


Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0
has been opened read-only.
Model: HL-DT-ST DVDRAM GT51N (scsi)                                      
Disk /dev/sr0: 2877MB
Sector size (logical/physical): 2048B/2048B
Partition Table: mac
Disk Flags:

Number  Start  End     Size    File system  Name   Flags
 1      2048B  6143B   4096B                Apple
 2      870kB  4966kB  4096kB               EFI

George528 · 05-17-2021, 02:08 PM

Quote:

Originally Posted by themightydill

Well.
Press E in GRUB and edit (hd1) to (hd0)??

what exactly is this GRUB, a software? how do i get it?

colorpurple21859 · 05-17-2021, 02:10 PM

If it isn't in the boot partition /dev/sdb9 check your / partition and/or other partitions, maybe the boot partition didn't get mounted when grub was installed and/or the wrong partition was mounted at /boot.

George528 · 05-17-2021, 02:24 PM

Quote:

Originally Posted by George528

what exactly is this GRUB, a software? how do i get it?

still empty in root

i followed the instruction closely https://www.linuxfromscratch.org/lfs...er10/grub.html

but i didn't do this

Code:

 If you choose to do this, you will need to mount the separate partition, move all files in the current /boot directory
 (e.g. the linux kernel you just built in the previous section) to the new partition.

i also followed this instruction:
From GRUB's perspective, the kernel files are relative to the partition used. If you used a separate /boot partition, remove /boot from the above linux line. You will also need to change the set root line to point to the boot partition.
so i deleted the /boot from code like this:

Code:

cat > /boot/grub/grub.cfg << "EOF"
# Begin /boot/grub/grub.cfg
set default=0
set timeout=5

insmod ext2
set root=(hd0,2)

menuentry "GNU/Linux, Linux 5.10.17-lfs-10.1" {
        linux   /vmlinuz-5.10.17-lfs-10.1 root=/dev/sda2 ro
}
EOF

themightydill · 05-17-2021, 04:21 PM

Quote:

Originally Posted by George528

what exactly is this GRUB, a software? how do i get it?

GRUB is the bootloader: the menu that comes up at boot saying "which OS to boot from?"

themightydill · 05-17-2021, 04:22 PM

Quote:

Originally Posted by George528

what exactly is this GRUB, a software? how do i get it?

GRUB is the menu that comes up when you boot.

colorpurple21859 · 05-17-2021, 05:18 PM

at the grub menu press c for a grub prompt grub>
at the grub prompt

Code:

grub>set

post the following line

Code:

prefix=

In post 9 you say your mounting /dev/sda9 to /boot but according to your grub.cfg /dev/sda2 is the partition where your kernel is located not /dev/sda9

Which partition is suppose to be the / partition?