Com Sci 501
System Administration in Linux

Department of Computer Science
The University of Chicago

Booting a Linux Rescue System

In the process of compiling a new kernel, or when installing and configuring other system software at the same time, it is easy to create a configuration where even the old stable kernel image won't work because of incompatibility with code outside the kernel. I have experienced such incompatibility with modules, but there are probably other sources of trouble that I haven't encountered yet. If you are unable to repair system damage through a stable kernel, you need to boot a rescue system from a different diskette than your normal Linux/LILO boot diskette. We say, ``rescue system'', rather than ``rescue kernel'', because the system includes application software to let you repair the damage that led you to use the rescue system. This application software is usually a small subset of the applications in your normal system. The file system from your normal Linux system can be mounted in a slightly odd location, often called ``/target''. In order to fit on a single diskette, the rescue system must carefully choose stripped down versions of essential software, so you will be frustrated by the lack of commands that you are accustomed to use. If your BIOS allows booting from CD-ROM, you may be able to use a full-featured rescue system.

Preparing a rescue system diskette

It is crucial to your happiness as a Linux user/administrator to prepare and test a rescue system diskette as soon as you have installed Linux, and keep it forever by your computer. Fortunately, the Debian installation diskette is an excellent rescue diskette, too. Don't lose it.

If you should lose your rescue diskette, or for some reason it doesn't work, there are rescue diskettes available on WWW. Get back to a Web browser under Windows, fetch a rescue system and write it to diskette. Hope that it is sufficient for your needs. [Perhaps someone will fill in more useful detail here.]

Booting a rescue system from diskette

This is the easy part. Eject any other diskette, and load the rescue system diskette in the floppy drive. Then reboot Linux as gracefully as possible (see Shutting Down and Rebooting Linux), to minimize additional damage.

Using the Debian installation/rescue disk

[I need to detail the steps for getting to a sensible login shell and mounting the file system from the Debian installation/rescue disk, since the obvious path through the interaction is for installation, not rescue.]

Booting a rescue system from CD-ROM

If your BIOS system allows booting from CD-ROM (most do not), and if you have a bootable system on CD-ROM, you are in luck, since you will probably get a very full-featured rescue system. Perhaps we will discover more about this possibility during the autumn quarter.