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. ______________________________________________________________________ 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 ______________________________________________________________________ 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 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 configu­ ration. 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 win­ dows95 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 recom­ mended that you use chroot, instead of lilo -r, as it is more conve­ nient 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. · 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 · You must keep the Yard rescue and boot floppy disk handy. Visit · Backup /root and /boot directories. Boot the Tomsrtbt floppy 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 ___________________________________________________________________ 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 - · Mini Lilo HOWTO at · Bootdisk-HOWTO at · Pre-made boot disks at · Tomsrtbt boot floppy disk · Yard rescue and boot floppy disk · BootPrompt-HOWTO at · Multiboot with LILO mini HOWTO at · Linux+WinNT mini HOWTO at · Linux goodies main site · Linux goodies mirror site · Vim color text editor for C++, C 3. 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