LILO, Linux Crash Rescue HOW-TO

LILO, Linux Crash Rescue HOW-TO
Al Dev (Alavoor Vasudevan) [email protected]
v6.0, 25 Dec 2000

This document discusses methods to recover from Linux system failures.
Various reasons for linux system failures can be - LILO is destroyed,
or linux fails to boot, or Master Boot Record (MBR) is damaged or
linux fails to boot when another operating system like Windows NT is
installed which erases LILO or MBR.
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Table of Contents

1. Introduction

1.1 Quick Steps to recovery
1.2 Precautionary measures
1.3 Removing LILO
1.4 Common mistakes

2. Related URLs

3. Other Formats of this Document

4. Copyright

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1. Introduction

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.

1.1. Quick Steps to recovery

Follow these steps to recover from LILO or system failures.

1. SCENE 1: If your system does not boot -

Get the tomsrtbt floppy <http://www.toms.net/rb> Boot with
tomsrtbt floppy Use fdisk to find the partitions. Try to recognise
the root partition by doing this -

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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
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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 configu�
ration.

In my case the root partition is /dev/hda4 which is used in the
examples below:

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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
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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 win�
dows95 directory.

Edit /etc/fstab (not /hda4/etc/fstab) and put (sample code given here)
-

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/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
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2. 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.

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bash# mount -a
bash# chroot /hda4 /sbin/lilo -q
bash# man chroot
bash# chroot /hda4 /sbin/lilo
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Alternatively, you can directly use /sbin/lilo instead of chroot. The
-r option of lilo actually does chroot. It is very strongly recom�
mended that you use chroot, instead of lilo -r, as it is more conve�
nient and can catch errors more easily.

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bash# man lilo
bash# /sbin/lilo -r /hda4
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3. 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.

4. 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 -

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bash$ man mkbootdisk
bash# cp /etc/lilo.conf /etc/lilo-original.conf
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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 -

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bash# mkbootdisk /dev/fd0
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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

5. SCENE 5: This is the worst scenerio, hopefully you do not come to
this stage. Scenes from 1 to 4 take care of majority of cases. But
in case above scenes 1, 2, 3 and 4 all fail then -

Step 1: Boot tomsrtbt and mount the partitions and backup the root
partition to another partition having disk space with comamnds -

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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
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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 -

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bash$ man mkbootdisk
bash# cp /etc/lilo.conf /etc/lilo-original.conf
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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 -

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bash# mkbootdisk /dev/fd0
bash# cp /etc/lilo-original.conf /etc/lilo.conf
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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.

1.2. Precautionary measures

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 -

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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
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� You must keep the tomsrtbt boot floppy handy. Visit
<http://www.toms.net/rb>

� 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 and
then

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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
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1.3. Removing LILO

You can replace the boot sector with the DOS boot loader by issuing
the DOS command at MS DOS prompt:

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FDISK /MBR
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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'.

1.4. Common mistakes

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 -

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bash# lilo -v -v -v
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2. Related URLs

Visit following locators which are related to LILO, Rescue Linux,
crash recovery -

� Mini Lilo HOWTO at <http://www.linuxdoc.org/HOWTO/mini/LILO.html>

� Bootdisk-HOWTO at <http://www.metalab.unc.edu/LDP/HOWTO/Bootdisk-
HOWTO/index.html>

� Pre-made boot disks at <http://www.linuxdoc.org/HOWTO/Bootdisk-
HOWTO/a1277.html>

� Tomsrtbt boot floppy disk <http://www.toms.net/rb>

� Yard rescue and boot floppy disk
<http://www.croftj.net/~fawcett/yard>

� BootPrompt-HOWTO at <http://www.linuxdoc.org/HOWTO/BootPrompt-
HOWTO.html>

� Multiboot with LILO mini HOWTO at
<http://www.linuxdoc.org/HOWTO/mini/Multiboot-with-LILO.html>

� Linux+WinNT mini HOWTO at
<http://www.linuxdoc.org/HOWTO/mini/Linux+WinNT.html>

� Linux goodies main site <http://www.aldev.8m.com>

� Linux goodies mirror site <http://aldev.webjump.com>

� Vim color text editor for C++, C
<http://metalab.unc.edu/LDP/HOWTO/Vim-HOWTO.html>

3. Other Formats of this Document

This document is published in 11 different formats namely - DVI,
Postscript, Latex, Adobe Acrobat PDF, LyX, GNU-info, HTML, RTF(Rich
Text Format), Plain-text, Unix man pages, single HTML file and SGML.

� You can get this HOWTO document as a single file tar ball in HTML,
DVI, Postscript or SGML formats from -
<ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO/other-formats/>

� Plain text format is in:
<ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO>

� Translations to other languages like French, German, Spanish,
Chinese, Japanese are in
<ftp://sunsite.unc.edu/pub/Linux/docs/HOWTO> Any help from you to
translate to other languages is welcome.

The document is written using a tool called "SGML-Tools" which can
be got from - <http://www.sgmltools.org> Compiling the source you
will get the following commands like

� sgml2html LILO-crash-rescue-HOWTO.sgml (to generate html file)

� sgml2rtf LILO-crash-rescue-HOWTO.sgml (to generate RTF file)

� sgml2latex LILO-crash-rescue-HOWTO.sgml (to generate latex file)

LaTeX documents may be converted into PDF files simply by producing a
Postscript output using sgml2latex ( and dvips) and running the output
through the Acrobat distill ( <http://www.adobe.com>) command as
follows:

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bash$ man sgml2latex
bash$ sgml2latex filename.sgml
bash$ man dvips
bash$ dvips -o filename.ps filename.dvi
bash$ distill filename.ps
bash$ man ghostscript
bash$ man ps2pdf
bash$ ps2pdf input.ps output.pdf
bash$ acroread output.pdf &
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Or you can use Ghostscript command ps2pdf. ps2pdf is a work-alike for
nearly all the functionality of Adobe's Acrobat Distiller product: it
converts PostScript files to Portable Document Format (PDF) files.
ps2pdf is implemented as a very small command script (batch file) that
invokes Ghostscript, selecting a special "output device" called
pdfwrite. In order to use ps2pdf, the pdfwrite device must be included
in the makefile when Ghostscript was compiled; see the documentation
on building Ghostscript for details.

This howto document is located at -

� <http://sunsite.unc.edu/LDP/HOWTO/LILO-crash-rescue-HOWTO.html>

Also you can find this document at the following mirrors sites -

� <http://www.caldera.com/LDP/HOWTO/LILO-crash-rescue-HOWTO.html>

� <http://www.WGS.com/LDP/HOWTO/LILO-crash-rescue-HOWTO.html>

� <http://www.cc.gatech.edu/linux/LDP/HOWTO/LILO-crash-rescue-
HOWTO.html>

� <http://www.redhat.com/linux-info/ldp/HOWTO/LILO-crash-rescue-
HOWTO.html>

� Other mirror sites near you (network-address-wise) can be found at
<http://sunsite.unc.edu/LDP/hmirrors.html> select a site and go to
directory /LDP/HOWTO/LILO-crash-rescue-HOWTO.html

In order to view the document in dvi format, use the xdvi program. The
xdvi program is located in tetex-xdvi*.rpm package in Redhat Linux
which can be located through ControlPanel | Applications | Publishing
| TeX menu buttons. To read dvi document give the command -

xdvi -geometry 80x90 howto.dvi
man xdvi

And resize the window with mouse. To navigate use Arrow keys, Page
Up, Page Down keys, also you can use 'f', 'd', 'u', 'c', 'l', 'r',
'p', 'n' letter keys to move up, down, center, next page, previous
page etc. To turn off expert menu press 'x'.

You can read postscript file using the program 'gv' (ghostview) or The
ghostscript program is in ghostscript*.rpm package and gv program is
in gv*.rpm package in Redhat Linux which can be located through
ControlPanel | Applications | Graphics menu buttons. The gv program is
much more user friendly than ghostscript. Also ghostscript and gv are
available on other platforms like OS/2, Windows 95 and NT, you view
this document even on those platforms.

� Get ghostscript for Windows 95, OS/2, and for all OSes from
<http://www.cs.wisc.edu/~ghost>

To read postscript document give the command -

gv howto.ps
ghostscript howto.ps

You can read HTML format document using Netscape Navigator, Microsoft
Internet explorer, Redhat Baron Web browser or any of the 10 other web
browsers.

You can read the latex, LyX output using LyX a X-Windows front end to
latex.

4. Copyright

Copyright policy is GNU/GPL as per LDP (Linux Documentation project).
LDP is a GNU/GPL project. Additional requests are that you retain the
author's name, email address and this copyright notice on all the
copies. If you make any changes or additions to this document then you
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