[HOW TO] Get Your *nix Bootloader Back

By Hurmoth
in HOW TO & FAQ Guides

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Grand Master

Hurmoth

Posted
Posted (edited)

I saw where Aaron had written the HOWTO Guide for getting the Windows bootloader back, but what if you're someone who needs their GRUB or LILO back? What then? Well, I found the answer for anyone who might need it :D

GRUB

  1. Boot into the first CD
  2. Type linux rescue when asked what to boot.
  3. After you have chosen Language and Keyboard layout, you are asked if you want to mount your harddisk system. Say yes to this.
  4. Now you system is mounted as /mnt/sysimage. Say 'OK'. Now type: chroot /mnt/sysimage. This will make you run on your already installed system, instead of the CD-ROM
  5. Type /sbin/grub-install /dev/hda (change hda to sda if you're using an SATA hard drive)

LILO

  1. Boot into the first CD
  2. Type linux rescue when asked what to boot.
  3. After you have chosen Language and Keyboard layout, you are asked if you want to mount your harddisk system. Say yes to this.
  4. Now you system is mounted as /mnt/sysimage. Say 'OK'. Now type: chroot /mnt/sysimage. This will make you run on your already installed system, instead of the CD-ROM. Now you can edit /etc/lilo.conf if something was wrong (vi /etc/lilo.conf and run lilo), or if you need to reinstall LILO just type lilo. The LILO installation process should now run.

This may be different for different distros and how you may have your system setup. I do not issue any guarantees with this HOWTO. Neowin, nor myself, is responsible if you bork your system. If you have any problems post them here ;)

Edited by Hurmoth
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Grand Master

MrA

Posted
Posted

Just an addendeum. You can install GRUB from within GRUB (this is how I like to do it).

1. Boot from a floppy or CD which uses GRUB as it's bootloader.

2. When you see GRUB's boot-menu, hit 'c'. You should see a "grub>" prompt

3. Type the following commands:

grub> root (hd0, 0)
grub> setup (hd0)

Commands explained:

"root (hd0, 0)" - This tells grub where it can find grub's files which are normally located in "/boot/grub/". The sample command tells grub that the files are located on the first hard drive, on partition 0 (first partition). If you don't know which drive/partition hold grub's files, you can do a:

grub> find /boot/grub/stage1

"setup (hd0)" - Tells grub to install itself on the Master Boot Record (MBR) of the first hard drive. You can also tell grub to install onto a partition by doing a "setup (hd0, 1)". This will tell grub to install to the second partition of the first hard drive.

Tips:

- Grub has a "help" command. Use it.

- Grub supports "bash-like" auto-completing. Say you don't quite know the partition number of your linux partition, but you know it's on the first hard drive and you know it's an ext2 partition. You can type:

grub> root (hd0,

and hit [tab]

This gives me:

Possible partitions are:
   Partition num: 0,  Filesystem type is reiserfs, partition type 0x83
   Partition num: 1,  Filesystem type is ext2fs, partition type 0x83
   Partition num: 2,  Filesystem type is reiserfs, partition type 0x83

Voila! It's partition number 1. Auto-completeing also works for other grub commands.

Grand Master

Hurmoth

Posted
  • Author
Posted
  markjensen said:
Anyone have an addition for doing this for LILO users?

585974127[/snapback]

If anyone adds it, I'll change the title and add it to my first post (giving the person credit of course) ;)

  markjensen said:
Good idea to have this posted (Y)  I have never had to do this, but many others have had to and have posted questions on it.

My boss' GRUB got messed up and wouldn't boot so I had to research how to fix it. The first place I looked was here and all I saw was Armeck's guide to getting the Windows bootloader back.

Grand Master

Kreuger

Posted
Posted

Yes this is a good post. My grub was messed too (error 18) and I couldn't fix it because Linspire Live couldn't detect my damn hard drive for some reason so I couldn't fix it. Also, when I attempted to go into linuxrecovery of the Debian cd, it wouldn't let me reinstall grub from there.

Grand Master

Hurmoth

Posted
  • Author
Posted

I added a way to reinstall LILO using the first installation disc, this can also be done with a Rescue Disc or Floppy Disk. I have never used LILO, so early this morning I installed a fresh copy of FC3 and used LILO instead of GRUB and messed it up on purpose to try and find out how to reinstall LILO... and that is what I came up with. Let me know if I have any typos :D

  • 7 months later...
Grand Master

markwolfe Veteran

Posted
  • Veteran
Posted
  invalidbuffalo said:

I get the error:

/dev/hda: Not found or not a block device.

when I try to reinstall GRUB.

If you do an fdisk -l (that is a lowercase letter "L", not the number one), what do you get for drives listed? Do you have SATA drives?

  • 4 months later...
Grand Master

Barney T. Administrators

Posted
  • Administrators
Posted
  wildworld_ammsa said:

i think this topic needs to be a Sticky. if some admin agrees, can he/she plz add it?

[Pinned]

This may not stay, but we'll see. There is a limit as to how many topics we can "pin". This is a good topic to have handy. :woot:

Barney

  • 4 weeks later...
  • 2 months later...
  • 1 month later...
Explorer

stylemessiah

Posted
Posted

Why lose it in the first place?

Its easy to avoid the entire unpleasantness when installing Linux onto a PC thats already hosts Windows, you just have to think about not upsetting precious windows, after all, its more finicky about its bootsector than Linux is.

Here's what i do:

Install linux.....wait until bootloader setup

Then

* Modify setting if needed to put bootloader on root partition (the partition that hosts \)

Then AFTER bootloader is written and anytime BEFORE you complete installation reboot:

* Switch to a terminal window form the setup GUI, on SuSE 10.1 for example i use CRTL ALT + F5.

* Put a floppy disk in your floppy drive

* Make a folder under /mnt, e.g. md /mnt/floppy (on some linuces, you may need to make an entirely different folder than floppy, as one may already exist and not be able to be written to - dont ask why, ive seen it, in this case try md /mnt/fdtemp etc.)

* Mount your floppy disk, e.g. mount -t vfat /dev/fd0 /mnt/floppy

* Type: dd if=/dev/hdaX of=/mnt/floppy/bootsec.lnx bs=512 count=1

Where X = the root partition number (e.g. /dev/hda11 as it is on mine)

* Browse to the floppy and make sure the bootsec.lnx file is there.

* Complete linux install and reboot into Windows

* Copy bootsec.lnx to c:\

* Keep floppy in a safe place, or copy the bootsec.lnx to a safe place.

* Open boot.ini in notepad

* Add "XXXX Linux" = c:\bootsec.lnx in the OS list under windows.

Where XXXX is the name of the linux or something witty and anti MS

* Save the file.

* Enjoy.

A few seconds work and thinking intelligently means you can avoid the whole bootsector drama completely and not upset either. I havent met a linux yet this isnt possible to use on.

As i said ive been using this since my first forays into Red Hat and Windows 2000, hasnt failed me yet.

Why lose it in the first place?

Its easy to avoid the entire unpleasantness when installing Linux onto a PC thats already hosts Windows, you just have to think about not upsetting precious windows, after all, its more finicky about its bootsector than Linux is.

Here's what i do:

Install linux.....wait until bootloader setup

Then

* Modify setting if needed to put bootloader on root partition (the partition that hosts \)

Then AFTER bootloader is written and anytime BEFORE you complete installation reboot:

* Switch to a terminal window form the setup GUI, on SuSE 10.1 for example i use CRTL ALT + F5.

* Put a floppy disk in your floppy drive

* Make a folder under /mnt, e.g. md /mnt/floppy (on some linuces, you may need to make an entirely different folder than floppy, as one may already exist and not be able to be written to - dont ask why, ive seen it, in this case try md /mnt/fdtemp etc.)

* Mount your floppy disk, e.g. mount -t vfat /dev/fd0 /mnt/floppy

* Type: dd if=/dev/hdaX of=/mnt/floppy/bootsec.lnx bs=512 count=1

Where X = the root partition number (e.g. /dev/hda11 as it is on mine)

* Browse to the floppy and make sure the bootsec.lnx file is there.

* Reboot into Windows

* Copy bootsec.lnx to c:\

* Keep floppy in a safe place, or copy the bootsec.lnx to a safe place.

* Open boot.ini in notepad

* Add "XXXX Linux" = c:\bootsec.lnx in the OS list under windows.

Where XXXX is the name of the linux or something witty and anti MS

* Save the file.

* Enjoy.

A few seconds work and thinking intelligently means you can avoid the whole bootsector drama completely and not upset either. I havent met a linux yet this isnt possible to use on.

As i said ive been using this since my first forays into Red Hat and Windows 2000, hasnt failed me yet.

  • 3 months later...
Collaborator

HT2791

Posted
Posted

i really didn't understand the first post (i'm new to linux).

i had to reinstall winxp because dual booting Ubuntu corrupted winxp files.

I got it back by:

Boot the livecd.

Start a terminal.

sudo -i

grub

find /boot/grub/stage1 // Will print something like (hd0,1)

root (hd0,1)

setup (hd0)

quit

was easy for me :)

  • 1 month later...
Neowinian

Biffa001

Posted
Posted

Hi,

  Quote
Boot the livecd.

Start a terminal.

sudo -i

grub

find /boot/grub/stage1 // Will print something like (hd0,1)

root (hd0,1)

setup (hd0)

quit

I already had winxp installed on my PC and have just installed the latest Ubuntu 7.04, immediately upon reboot I received a grub error 22 and nothing booted! Thanks to my PDA net access and this forum I got my windows bootloader back and then have just followed the above info to try and get a boot screen back to be able to choose either winxp or ubuntu but with no joy.

I just tried the above and it all seemed to go ok (no errors within the terminal window), but when I rebooted my PC it just started up straight into windows xp again....!

Help!

  • 2 years later...
Grand Master

DjmUK

Posted
Posted

For GRUB2 under Ubuntu 9.10 I had to do the following after I broke my bootloader. It kept loading up the memtest after I played around with startupmanager and GRUB2 provided NO menu to choose the kernel :\

  1. Boot via LiveCD
  2. sudo fdisk -l (list hard drives)
  3. sudo mount /dev/sda1 /mnt (mount the hard drive)
  4. sudo mount --bind /dev /mnt/dev (mount other devices)
  5. sudo chroot /mnt (great power comes great responsibility)
  6. gedit /etc/default/grub (this loads up the GRUB2 options)
  7. Change GRUB_DEFAULT=3 to GRUB_DEFAULT= (aka first kernel in grub.cfg, mine was 3 pointing at memtest)
  8. update-grub (this updates that read-only /boot/grub/grub.cfg file)
  9. shutdown -r now (reboots your baby)

That's the procedure that worked for me, I have a single hdd with no special partitioning (just default installed).

All the above is broken down from the Wiki Grub2 page.

  • 5 years later...
Mentor

Radium

Posted
Posted

Speaking of bootloaders!

 

I opted out from using GRUB (or other chain loaders) and use the EFI stub in the Linux kernel and then use efibootmgr to add the kernel and the parameters as a boot entry. I don't find a reason to load a bootloader which then loads the OS when you can make UEFI load the OS directly.

If the kernel gets damaged or you screw up the parameters then you can use the EFI shell (comes with the board) to manually load the kernel.

 

What I do is:

  Quote

 

efibootmgr -b 0000 -d /dev/sda -p 1 -c -L "Arch Linux EFI stub" -l /vmlinuz-linux -u "root=UUID=3e65a7c4-0a24-44d5-aeeb-e6da72343a34 rootfstype=btrfs rootflags=ssd,discard,noatime,space_cache,compress=lzo,autodefrag,subvol=archrootfs rw quiet initrd=/initramfs-linux.img"

The 0000 is the boot entry in the UEFI boot entry list index. The boot order can be chosen with efibootmgr. I only have two entries, 0000 and 0002 (EFI shell).

The EFI system partition is partition 1 (-p 1, which is default) on HD 0 (-d /dev/sda) and is mounted at /boot in the OS. Add the custom text and then tell it which file to load (-l /vmlinuz-linux).

You can't overwrite a boot entry so you have to delete the entry first. Not specifying the list index ("bootnum") and using the -c option (create) will make it create a new entry at a unused index.

I would highly recommend this if you don't have a lot of operating systems to boot or non-UEFI compliant operating systems. Sure, having custom boot entries for failsafe or recovery modes won't be there but you can create entries for those too or even create shell commands that you can use in the EFI shell. The wiki for Arch Linux covers this subject and works on all kernels that has the EFI stub compiled into it.

 

Requirements: GPT on the drive and a UEFI system patition (a minimum 100MB or more depending on the size of the kernel(or kernels you want to load) and the standard says that it SHOULD be the first partition on the disk.

 

BTW: Don't mind the autodefrag root mount option, it only defrags metadata, it removes dead meta data, moves meta data etc, and does not do actual sector defragmentation.

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