Faults in memory modules may cause your system to freeze or crash unpredictably. In some cases, memory faults may only cause errors with particular combinations of software. For this reason, you should test the memory of a computer before you install Fedora for the first time, even if it has previously run other operating systems.

To boot your computer in memory testing mode, enter memtest86 at the boot: prompt. The first test starts immediately. By default, memtest86 carries out a total of ten tests.

To halt the tests and reboot your computer, enter Esc at any time.

You may boot a command-line Linux system from either a rescue disc or the first installation disc, without installing Fedora on the computer. This enables you to use the utilities and functions of a running Linux system to modify or repair systems that are already installed on your computer.

The rescue disc starts the rescue mode system by default. To load the rescue system with the first installation disc, enter:

 linux rescue

Specify the language, keyboard layout and network settings for the rescue system with the screens that follow. The final setup screen configures access to the existing system on your computer.

By default, rescue mode attaches an existing operating system to the rescue system under the directory /mnt/sysimage/.