LILO, Linux Crash Rescue HOW-TO

Al Dev (Alavoor Vasudevan) alavoor@yahoo.com

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.

1. Introduction

2. Related URLs

3. Other Formats of this Document

4. Copyright


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 -


    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
    

  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.


    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
    

  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 -


    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 /dev/fd0
    

    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 -


            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 /dev/fd0
    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.

1.2 Precautionary measures

You should take the following pre-cautionary measures to tackle the problems in future.

1.3 Removing LILO

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'.

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 -


bash# lilo -v -v -v


2. Related URLs

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


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.

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

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:


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 &

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 -

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

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 'ghostscript'. 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.

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 please intimate all the authors of this document. Brand names mentioned in this document are property of their respective owners.