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.
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 and boot partition. Watch out, you may be having the /boot files on
the root partition itself.
The Linux's root partition has the following directories
bin,
boot,
etc,
usr.
And the Linux's boot partition has these directories:
vmlinuz,
boot.b,
chain.b,
map.
To find out root partition do this :
bash# fdisk /dev/hda
Command (m for help): m (Gives you help on commands)
Command (m for help): p (Gives you list of partitons)
Command (m for help): q
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.
Keep trying hda3, hda4, hda5, etc.. untill you find the root partition.
If you do not find root partition in hda device then repeat the above
steps for other hard disk devices like hdb, hdc, hdd etc..
Next, you should find the /boot, /usr and /var partitions.
The disk locations of these partitions are needed to create the new lilo configuration.
In my case the root partition is /dev/hda4 which is used in the examples below:
bash# mkdir /rootpart
bash# mount /dev/hda4 /rootpart
bash# cat /rootpart/etc/fstab
Read the output of fstab and mount partitions as per fstab file, see below -
bash# mount /dev/hda5 /rootpart/boot
bash# mount /dev/hda6 /rootpart/usr
bash# mount /dev/hda7 /rootpart/var
bash# mount /dev/hda8 /rootpart/opt
bash# mount /dev/hda9 /rootpart/root
bash# mount /dev/hda10 /rootpart/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 (FAT16 partition).
Edit /etc/fstab (not /rootpart/etc/fstab) and put (sample code given here) -
/dev/hda4 /rootpart ext2 defaults 1 1
/dev/hda5 /rootpart/boot ext2 defaults 1 1
/dev/hda6 /rootpart/usr ext2 defaults 1 1
/dev/hda7 /rootpart/var ext2 defaults 1 1
/dev/hda8 /rootpart/opt ext2 defaults 1 1
/dev/hda9 /rootpart/root ext2 defaults 1 1
/dev/hda10 /rootpart/home ext2 defaults 1 1
/dev/hda11 /rootpart/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 /rootpart/win95part
bash# mount /rootpart/win95part
And repair the problem partitions 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.
After executing steps in scene 1 above, you should have
already mounted /rootpart and have created /etc/fstab file.
Note: It is very important to note how chroot command works below. The /sbin/lilo
file which chroot uses is actually located in /rootpart/sbin/lilo and
NOT in /sbin!! Hence, do not get confused.
bash# mount -a
bash# chroot /rootpart /sbin/lilo -q
bash# man chroot
bash# chroot /rootpart /sbin/lilo
Note: New users of chroot will be confused. If chroot command complains that
it cannot find /boot/map file then it actually
means it that it cannot find /rootpart/boot/map. Because you gave /rootpart as the
first argument to chroot and all references are with respect to /rootpart.
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 /rootpart
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.
Or get boot disks for Linux/NT/Windows/DOS/Mac are at
http://www.bootdisk.com
Other option is - get a hold of installation Linux-CDROM. Just about every Linux distribution
provides a image of a rescue disk on their CD. Under Linux use
"dd if=/cdrom/disks/rescue of=/dev/fd0" to create a rescue floppy disk. Under DOS
use rawrite.exe (included on Linux CD) and then do "rawrite image-name a:".
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 /rootpart ext2 defaults 1 1
/dev/hda11 /b1 vfat defaults 1 1
bash$ mkdir /rootpart; mount /rootpart
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 /rootpart
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 -
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 backup the partition tables setup to a floppy and to a hard disk.
You should also print this out and paste it on the computer box.
bash$ su - root
bash# man fdisk
bash# fdisk -l /dev/sda > partition_table_backup.txt
Very helpful if you need to repartition the hard disk.
From the printout, you would know where your partition starts.
During recovery, after repatitioning and formating you can restore data from the backup.
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