[SOLVED] Reinstall grub bootloader

xiongnu · 06-09-2015, 01:45 PM

hi,

I've got a Thinkpad laptop that is loaded with WinXP/Debian8. in the process of adding FreeBSD to the mix, the grub bootloader was replaced by FreeBSD's boot loader 'boot0cfg', and it doesn't detect Linux partition and I can no longer boot into Debian.

i tried to reinstall grub by using both 'netinstall' and full image of Debian8 installation.

with 'netinstall', I can get to 'rescue mode'(under 'Advanced option' on the main menu), but it returns error about not detecting a valid kernel image.

on full image (live cd version), it doesn't list rescue under 'Advanced Option' at main menu.

which image file contains 'rescue mode' so I can recover the debian bootloader?

Head_on_a_Stick · 06-09-2015, 02:12 PM

NOTE: The advice below presumes that Debian is not installed in EFI-mode.

Load up a live ISO and use these commands to chroot into your system from the live environment:

Code:

# mkdir /target
# mount /dev/sdXY /target
# for i in /sys /proc /dev; do mount --bind $i /target$i; done
# chroot /target /bin/bash
# source /etc/profile
# grub-install /dev/sdX
# update-grub

Replace "X" with the drive letter assigned to your Debian HDD and replace "Y" with the partition number of your root partition.

If you have a separate /boot partition, you will have to mount that as well before running the `chroot` command (and after you mount the root partition).

Code:

# mount /dev/sdXZ /target/boot

Where "Z" is the partition number of your /boot partition.

You will have to write a custom menu entry for FreeBSD -- add this to the end of the file at /etc/grub.d/40_custom

Code:

menuentry 'FreeBSD {
    set root='(hdX,A)'
    chainloader +1
}

Replace "A" with the partition containing your FreeBSD system and use `update-grub` to add the custom entry to your GRUB menu.

xiongnu · 06-12-2015, 01:07 PM

Quote:

Originally Posted by Head_on_a_Stick

If you have a separate /boot partition, you will have to mount that as well before running the `chroot` command (and after you mount the root partition).

Code:

# mount /dev/sdXZ /target/boot

Where "Z" is the partition number of your /boot partition.

here's the partition info by 'fdisk' and output of os-prober(before I installed 'boot0cfg' and can still boot into Debian). Master boot record is on windows partition. Does this mean /boot partition is 'sda1' and I need to mount it before 'chroot'?

Code:

Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x9f114bc6

Device     Boot     Start       End  Sectors  Size Id Type
/dev/sda1              63  62929439 62929377   30G  7 HPFS/NTFS/exFAT
/dev/sda2  *    106027047 143775701 37748655   18G a5 FreeBSD
/dev/sda3       143806320 156295439 12489120    6G  c W95 FAT32 (LBA)
/dev/sda4        62930942 106027007 43096066 20.6G  f W95 Ext'd (LBA)
/dev/sda5        62930944  82460671 19529728  9.3G 83 Linux
/dev/sda6        82462720  85053439  2590720  1.2G 82 Linux swap / Solaris
/dev/sda7        85055488 106027007 20971520   10G 83 Linux

Partition table entries are not in disk order.
erdos@debian:~$ os-prober
unshare failed: Operation not permitted
rm: cannot remove ‘/var/lib/os-prober/labels’: Permission denied
erdos@debian:~$ sudo os-prober
/dev/sda1:Microsoft Windows XP Professional:Windows:chain
/dev/sda3:Windows NT/2000/XP:Windows1:chain
erdos@debian:~$ 
erdos@debian:~$

Head_on_a_Stick · 06-12-2015, 01:49 PM

Quote:

Originally Posted by xiongnu

Master boot record is on windows partition. Does this mean /boot partition is 'sda1' and I need to mount it before 'chroot'?

To clarify: the "Master Boot Record" is on the very first sectors of the disk and holds the partition table itself.
https://en.wikipedia.org/wiki/Master_boot_record

You can check if you have a separate /boot partition by running:

Code:

lsblk

This will show all the mountpoints in the right-most column with the block devices listed in the left-most column.

If you do not see "/boot" in the mountpoints column then you do not need to mount it.

If you do see "/boot" in the mountpoints column, then run:

Code:

# mount /dev/sdaX /target/boot

After the first `mount` command and before the `chroot` command.

Replace "X" with the partition number shown by `lsblk` (if it shows "/boot" as a mountpoint).

If this all seems a bit too much for you, you could also try the "SuperGRUB2" rescue disk:
http://www.supergrubdisk.org/

You will still need to add the FreeBSD custom entry yourself though as GRUB cannot read the BSD filesystems.

xiongnu · 06-12-2015, 04:15 PM

success! first part works flawlessly, I got 'grub' back and now I'm in Debian typing this message.

Code:

# mkdir /target
# mount /dev/sda5 /target
# for i in /sys /proc /dev; do mount --bind $i /target$i; done
# chroot /target /bin/bash
# source /etc/profile
# grub-install /dev/sda
# update-grub

second part generates error, here's my /etc/grub.d/40_custom:

Code:

menuentry 'FreeBSD {
    set root='(hda,2)'
    chainloader +1
}

error while run 'update-grub'

Code:

erdos@debian:~$ sudo update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-3.16.0-4-amd64
Found initrd image: /boot/initrd.img-3.16.0-4-amd64
Found Microsoft Windows XP Professional on /dev/sda1
Found unknown Linux distribution on /dev/sda2
Found Windows NT/2000/XP on /dev/sda3
error: out of memory.
error: syntax error.
error: Incorrect command.
error: syntax error.
Syntax error at line 216
Syntax errors are detected in generated GRUB config file.
Ensure that there are no errors in /etc/default/grub
and /etc/grub.d/* files or please file a bug report with
/boot/grub/grub.cfg.new file attached.
done
erdos@debian:~$

Head_on_a_Stick · 06-12-2015, 04:26 PM

Quote:

Originally Posted by xiongnu

second part generates error, here's my /etc/grub.d/40_custom:

Code:

menuentry 'FreeBSD {
    set root='(hda,2)'
    chainloader +1
}

I did say to add that to the end of 40_custom -- you need these lines at the top of the file:

Code:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

If it still doesn't work, you should probably mark this thread [SOLVED] and start a new thread about adding a FreeBSD entry to GRUB2.

I used to have a FreeBSD system booting from GRUB but it's gone now and I can't remember exactly what I used to create the entry.

EDIT: Also, it should be "set root='(hd0,2)'" rather than '(hda,2)'

xiongnu · 06-12-2015, 04:38 PM

that's correct, i appended the menuentry to the end of /etc/grub.d/40_custom.

Code:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

menuentry 'FreeBSD {
    set root='(hd0,2)'
    chainloader +1
}

the update-grub returned the same error when i use 'set root='(hd0,2)'

I've marked the thread solved, thanks a lot for the help!

Head_on_a_Stick · 06-12-2015, 04:49 PM

You're welcome

xiongnu · 06-12-2015, 04:53 PM

after i put freebsd in between double quotation " ", 'update-grub' runs without error. upon reboot, freebsd appears in grub and I can boot into it as well.

Code:

menuentry "FreeBSD" {
    set root='(hd0,2)'
    chainloader +1
}

thanks a lot, Head_on_a_Stick, you saved my day!

Head_on_a_Stick · 06-12-2015, 05:00 PM

Excellent news -- glad you got it sorted!