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You cannot avoid accidents and if it happens to linux systems then it
may damage the
master boot record (MBR) or LILO (Linux boot Loader).
There may be cases where linux will not boot due to hard disk
failures. The LILO may also fail if you accidentally re-partition the
hard disk or you install another additional operating system like
Windows 98/NT on the linux computer.
This document gives you some ideas, tips and quick guide to recover
fast without wading through hundreds of pages of documentation on
LILO or Linux.
To recover any Windows 95/NT/2000, OS/2, BeOS or Linux box you may need the
tiny linux which fits on a single floppy disk.
See the list of tiny floppy linux given below -
It is a good idea to backup the important system files like /etc/fstab, /etc/lilo.conf
after you login using Tomsrtbt floppy in next section. This can be very handy during
crash situation or something happens to system files.
bash# cp /etc/fstab /etc/fstab.orig
bash# cp /etc/lilo.conf /etc/lilo.conf.orig
bash# cp /etc/hosts /etc/hosts.orig
bash# cp /etc/hosts.allow /etc/hosts.allow.orig
bash# cp /etc/hosts.deny /etc/hosts.deny.orig
bash# cp /etc/inetd.conf /etc/inetd.conf.orig
bash# cp /etc/inittab /etc/inittab.orig
bash# cp /etc/networks /etc/networks.orig
Follow these steps to recover from LILO or system failures.
- SCENE 1: If your system does not boot -
Get the tomsrtbt floppy
http://www.toms.net/rb or MuLinux floppy
(see also
Tiny Linux).
Boot with tomsrtbt floppy
Use fdisk to find the partitions. Try to recognise the
root partition by doing this -
bash# fdisk /dev/hda
bash# mkdir /test
bash# mount /dev/hda1 /test
bash# ls /test
You should see root-partition list like this -
bin fd lib mnt proc sbin usr
boot dev etc home lost+found opt root tmp var
If this is not a root partition, then try the next partition /dev/hda2.
Next try hda3, hda4, hda5, etc.. untill you find the root partition.
Still not found in hda then repeat the above steps for other devices
like hdb, hdc, hdd etc..
Also the /usr, /var, and /boot partition are needed as these are
required to create new lilo configuration.
In my case the root partition is /dev/hda4 which is used in the examples below:
bash# mkdir /hda4
bash# mount /dev/hda4 /hda4
bash# cat /hda4/etc/fstab
Read the output of fstab and mount partitions as per fstab file, see below -
bash# mount /dev/hda5 /hda4/boot
bash# mount /dev/hda6 /hda4/usr
bash# mount /dev/hda7 /hda4/var
bash# mount /dev/hda8 /hda4/opt
bash# mount /dev/hda9 /hda4/root
bash# mount /dev/hda10 /hda4/home
In my case, as per fstab file hda5 was boot, hda6 was usr, hda7 was var, hda8 was opt,
hda9 was root, hda10 was home and hda11 was windows95 directory.
Edit /etc/fstab (not /hda4/etc/fstab) and put (sample code given here) -
/dev/hda4 /hda4 ext2 defaults 1 1
/dev/hda5 /hda4/boot ext2 defaults 1 1
/dev/hda6 /hda4/usr ext2 defaults 1 1
/dev/hda7 /hda4/var ext2 defaults 1 1
/dev/hda8 /hda4/opt ext2 defaults 1 1
/dev/hda9 /hda4/root ext2 defaults 1 1
/dev/hda10 /hda4/home ext2 defaults 1 1
/dev/hda11 /hda4/win95part vfat defaults 1 1
On my computer hda4 contains the linux root partition, hda5 had boot partition and
hda11 has windows 95 vfat system.
bash# mkdir /hda4/win95part
bash# mount /hda4/win95part
And repair the system using fsck or e2fsck commands.
bash# man fsck
bash# man e2fsck
- SCENE 2: If LILO is not working..
Follow scene 1 above, if that fails then follow these steps. Now you should have
already mounted /hda4 and have created /etc/fstab file.
bash# mount -a
bash# chroot /hda4 /sbin/lilo -q
bash# man chroot
bash# chroot /hda4 /sbin/lilo
Alternatively, you can directly use /sbin/lilo instead of chroot. The
-r option of lilo actually does chroot.
It is very strongly recommended that you use chroot, instead of lilo -r,
as it is more convenient and can catch errors more easily.
bash# man lilo
bash# /sbin/lilo -r /hda4
- SCENE 3: If LILO is not working..
If scene 1 and 2 failes, then
if you made the boot disk with 'mkbootdisk' (during install or
by using 'man mkbootdisk'), boot with it and repair your partitions.
The mkbootdisk is in mkbootdisk*.rpm package, you must install this.
- SCENE 4: If 1, 2 and 3 above fails and you do not have boot disk
If you have another computer running linux, then
login as root and do -
Note: If you compile your own kernel as a bzImage (for instance, bzImage-2.4.4),
then you should create a hard link to vmlinuz-2.4.4 as follows (note the
the z in name vmlinuz and it is not vmlinux). If you do not do this then
mkbootdisk command may fail.
bash# cd /boot
bash# ls -l vmlinuz*
bash# ln /boot/bzImage-2.4.4 /boot/vmlinuz-2.4.4
Now that you have bzImage and vmlinuz, give these commands -
bash$ man mkbootdisk
bash# cp /etc/lilo.conf /etc/lilo-original.conf
Edit the /etc/lilo.conf and put the root partition name as you
obtained in 'scene 1' above and insert a blank floppy and give -
bash$ mkbootdisk --device /dev/fd0 2.2.12-20
The mkbootdisk is in mkbootdisk*.rpm package, you must install this.
Make sure you move the /etc/lilo-original.conf back to /etc/lilo.conf!!
And then take this floppy and goto scene 3
- SCENE 5: This is the worst scenerio and hopefully you will never come to this
stage. Scenes from 1 to 4 will take care of majority of cases. But just in case, all the above
scenes 1, 2, 3 and 4 fail then -
Step 1:
Boot tomsrtbt
(see
Tiny Linux)
and mount the partitions and backup the root
partition to another partition having disk space with comamnds -
Edit /etc/fstab and put (sample code given here, you may have to
change as per your disk layout) -
/dev/hda4 /hda4 ext2 defaults 1 1
/dev/hda11 /b1 vfat defaults 1 1
bash$ mkdir /hda4; mount /hda4
bash$ mkdir /b1; mount /b1
bash$ cd /
bash$ df
And see that there is enough disk space in /b1 to tar up the root partition
bash$ tar cvf /b1/root-hda4.tar /hda4
Step 2:
Insert Linux cdrom, reboot and install the redhat linux
on /dev/hda4 (but DO NOT install any extra packages, you just
need to install only the root, boot systems and LILO manager that is, a very
bare minimum). This will also install the LILO on hard disk.
Boot linux now and login as root and do -
bash$ man mkbootdisk
bash# cp /etc/lilo.conf /etc/lilo-original.conf
Note: You MUST remember to copy back lilo-original.conf to lilo.conf!!
Edit the /etc/lilo.conf and put the root partition name as you
obtained in 'scene 1' above and insert a blank floppy and give -
bash$ mkbootdisk --device /dev/fd0 2.2.12-20
bash# cp /etc/lilo-original.conf /etc/lilo.conf
Test this boot floppy to see that this works and then
restore back the all the files which you backedup using tar on
/b1/root-hda4.tar as in step 1 above.
You should take the following pre-cautionary measures to tackle the
problems in future.
- You MUST make emergency boot disk from time to time and whenever you
make changes to the partition. Insert a blank floppy and do this -
bash$ man mkbootdisk
The mkbootdisk is in mkbootdisk*.rpm package, you must install this.
bash$ mkbootdisk --help
bash$ mkbootdisk --device /dev/fd0 2.2.12-20
- You must keep the tomsrtbt boot floppy handy. Visit
http://www.toms.net/rb
(see also
Tiny Linux)
- You must keep the Yard rescue and boot floppy disk handy. Visit
http://www.croftj.net/~fawcett/yard
- Backup /root and /boot directories. Boot the Tomsrtbt
floppy
(see also
Tiny Linux)
and then
bash# vi /etc/fstab
And put these lines -
/dev/hda1 /a1 vfat defaults 1 1
/dev/hdb1 /b1 vfat defaults 1 1
In my case hda1 had the linux root partition '/'
bash# cd /
bash# tar cvf /b1/linux-root-partition-hda1.tar a1
bash# tar cvf /b1/linux-boot-partition-hda1.tar a1/boot
You can replace the boot sector with the DOS boot loader by issuing the DOS
command at MS DOS prompt:
FDISK /MBR
where MBR stands for "Master Boot Record".
See also LILO documentation on linux at /usr/doc/lilo* for other methods of
uninstalling the LILO. And see also 'man lilo'.
After making changes to /etc/lilo.conf you MUST run lilo to make changes
to go in effect. It is a very common mistake committed by newusers. Type -
bash# lilo -v -v -v
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