Heavy-duty system repair tends to happen in rescue mode — a special boot option. The benefit of this option is that you can perform necessary system surgery even if your installed system is hopelessly broken. The drawback is that this is a purely command line interface — you really have to know your stuff to find your way around.
Appendix A contains a list of Linux commands to try to help you out. Chapter 22 addresses, among other things, how to fix your boot loaders from inside rescue mode (if your problem is with the boot loader), and how to track down the error messages your kernel may have left behind. You may also be able to find helpful tips by reviewing your distribution’s documentation and online help forums.
To enter rescue mode in Fedora (it’s text based, prepare for typing!), place the DVD or your first CD into your DVD-ROM or CD-ROM drive and boot the machine. Then follow these steps:
When the disk first loads, select Rescue Installed System from the menu and press Enter. This action begins booting the system into maintenance mode.
Select your language and press Enter.
Select your keyboard type and press Enter. The rescue system does its thing for a while, perhaps a minute or two on a slow system.
When asked whether you want to start the network interfaces, answer No unless you know you need to download something.
At the Rescue screen, select one of the three options offered, and then press Enter. Your three options are