This chapter explains how to install Red Hat Linux on a computer that currently runs another operating system, such as Microsoft Windows, and how to create a dual-boot environment.
If the computer you want to install Red Hat Linux on is currently running Windows (or some other operating system), you have an important decision to make. Your choices are:
Do you want to install Red Hat Linux but you are uncomfortable with disk partitioning? You can install Red Hat Linux on your system without creating any Linux partitions  by performing a partitionless installation. During a partitionless installation, the installation program will install Red Hat Linux on an existing, formatted Windows partition. You will only need to create a boot disk during the installation to access Red Hat Linux on your system.
This method is perfect for those who do not want to install Red Hat Linux as the primary OS or as a dual-boot OS on your system. It is a great way of trying out Red Hat Linux without creating Linux partitions on your system.
If this what you want to do, refer to the Official Red Hat Linux x86 Installation Guide for those instructions.
Do you want to install Red Hat Linux and then have the option of booting either Red Hat Linux or your other operating system? A workstation- or custom-class installation can be performed so that Red Hat Linux is installed on your system, without affecting the other operating system. In fact, a workstation-class installation will accomplish this by default. In a custom-class installation, you can install LILO (the LInux LOader) to boot Linux and the other operating system.
Install the other operating system first and then install Red Hat Linux. The Red Hat Linux installation program will usually detect the other operating system and automatically configure LILO to boot either Red Hat Linux or the other operating system. The Official Red Hat Linux x86 Installation Guide provides instructions on installing and configuring LILO. After the installation, whenever you start the computer, you can indicate whether you want to start Red Hat Linux or the other operating system.
Remember to back up all important information before configuring your system to boot more than one operating system. Be sure to create a boot disk for both operating systems in case the boot loader fails to recognize both of them.
The BIOS in some systems cannot access more than the first 1024 cylinders on a hard drive. If this is the case, the /boot Linux partition must be located on the first 1024 cylinders of your hard drive for LILO to boot.
If you want to dual-boot Red Hat Linux and Windows NT, you should install Windows NT first because it installs its own boot loader on the Master Boot Record (MBR). After installing Windows NT, if you install LILO during the Red Hat Linux installation program, the NT boot loader will be overwritten, but it should add a LILO entry labeled dos to boot Windows NT. Remember that a workstation-class installation automatically installs LILO to the MBR. Installing LILO on the MBR to boot Windows NT has been known to fail in some cases. If this is the case, you should perform a custom-class installation and install LILO on the first sector of the root partition instead of the MBR.
If you install LILO on the first sector of the root partition, be sure to create a boot disk. You will need to either use the boot disk to boot Red Hat Linux or configure the NT boot loader to boot LILO from the first sector of the root partition. For more information on configuring the NT boot loader, refer to http://www.linuxdoc.org/HOWTO/mini/Linux+NT-Loader.html.
If this what you want to do, read the section called Setting Up a Dual-Boot Environment.
Do you want Red Hat Linux to be the only operating system on your computer? Choose a server-class installation, choose a workstation-class installation and manually delete the DOS (Windows) partitions, or choose a custom-class installation and delete the existing DOS (Windows) partitions.
In order to install Red Hat Linux and keep another OS on your system, you must have sufficient space on which Red Hat Linux will be installed. Otherwise, Red Hat Linux will replace the current OS and files on your system. If you have not partitioned your hard drive to make room for Red Hat Linux or made sure that there is sufficient unpartitioned space available for your installation, Red Hat Linux will install over the existing information by default. This will also happen if you select a server-class installation. Unless you have sufficient room on your hard drive for Red Hat Linux, you cannot install it.
If this is what you want to do, first back up any information on your computer that you want to save or perform a full backup if you think you may want to restore your system to its original configuration, then proceed with the installation as explained in the Official Red Hat Linux x86 Installation Guide.
A partition is a physical division on a hard drive.