^V lot of things are happening when your system boots up. When started up, the Power On Self Test (POST) causes the computer to look for a bootable device. On this device, it will look for a valid boot record, usually written to the master boot record of the device. From there, it will start the boot loader, which on Linux by default is the Grand Unified Boot Loader (GRUB). The boot loader will in turn activate the kernel, which is helped by some drivers in its initial RAM drive (initrd, explained later in this chapter). From there, init, the mother of all processes, is loaded. This process reads its configuration file, inittab, to see what happens next. Usually this involves executing some boot scripts that always need to be executed and then activating the runlevel in which all services needed by your server are started. Once that is completed, your server generates a login prompt where the user can authenticate to the system.
This chapter discusses in detail all these phases of the boot procedure. This is important information, because it may help you troubleshoot your server when you find it's not booting properly. Also, it helps you activate services automatically when booting.
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