This chapter describes techniques for booting your Linux system. Depending on your hardware and whether you want to run any other operating systems, you can configure the system to automatically boot Linux or to provide a choice between several operating systems. Choosing between operating systems is generally referred to as dual booting, although you can select between more than two. We talk more about dual booting in the section Dual-Booting Linux and Windows 2000/XP/Vista in Dual-Booting Linux and Windows 2000/XP/Vista.
An alternative to dual booting is virtualization, where you run one or more virtual operating systems inside a real operating system. The real system is known as the host, and the virtual systems are known as guests. Virtualization makes it easy to switch between systems without having to reboot. Two ways to run virtual systems are to make Linux the host system with another operating system running in a virtual machine. See Chapter 15 for an overview of virtualization concepts and for information on how to run guest systems under Linux. You can also run Linux as a guest with another operating system such as Windows as the host. Two ways to do this are with Microsoft’s Virtual PC and VMware server. Both are free downloads and are available at www.microsoft.com and www.vmware.com, respectively.
Once your Linux system is installed, rebooting the system is generally straightforward. There are several possibilities for configuring your boot process. The most common choices are:
Boot Linux from a bootable disk, most likely a CD or an installation CD/DVD, leaving another operating system to boot from the hard drive.
Use GRUB (GRand Unified Bootloader), the GNU graphical boot loader and command shell. Like LILO, GRUB lets you boot both Linux and other operating systems. GRUB, which has additional functionality not found in LILO, is now the de facto Linux boot loader.
Whatever method you choose for booting, be sure to have a working boot disk available for emergency use. In particular, don’t experiment with the files and options in this chapter unless you have a boot disk, because any error could leave you unable to boot from the hard disk. Note, though, that one of the advantages of using GRUB is that if there is a problem booting from the menu, it drops you down to the command-line interface so you can enter commands directly and try to recover. In addition, your distribution CD or DVD undoubtedly has a recovery option on it. Or you can boot from a live Linux CD such as Knoppix.