Aproblem with booting your Linux system is probably one of the most serious malfunctions that can happen. If the system can’t load, its hard drives and

file systems won’t mount and its services won’t start. Essentially, the machine is rendered useless.

A system will fail to boot for many reasons. The most serious problem is a hardware malfunction, such as a hard drive or disk controller failure. Another problem that can prevent your machine from starting is corrupt files. A file system can be corrupted if it is not shut down properly; for example, if an administrator accidentally turns a server off without properly unmounting the file systems, they can easily become corrupted. Files can also become corrupt in the event of a power failure because the system has no time to close opened files and shut down properly. Another problem that can hinder your system boot is misconfigured software and hardware. For example, you may have made a mistake in the name of a file system in one of your boot configuration files, and the file system will not load.

A wide variety of tools and utilities are available to help you troubleshoot and fix a boot problem. This chapter deals with several of these tools, including system rescue boot disks, hard drive utilities, and system hardware and software status commands.

Examining the Startup Process

Between the time you turn the machine on and the time you get to login, the boot process goes through many different steps and stages to get to that point. Each step along the way can break down because of a hardware or software problem, which will prevent the system from booting at all. A good theoretical knowledge of the Linux boot process is essential when troubleshooting boot problems.

Boot process steps

The following is a list of events that transpire from the moment you start to boot the Linux system.

1.BIOS: The system’s BIOS (Basic Input Output System) initializes and performs internal checks on the hardware components of the system, including the CPU, memory, hard drives, and video system. If an error occurs with a component, the system will emit audible beeps and halt the process during initialization.

2.MBR: The system checks the MBR (Master Boot Record) of the boot hard drive, which loads into memory the boot manager for the system. In this case, the boot manager is LILO.

3.LILO: LILO stands for LInux LOader. LILO is a Linux boot manager, which is responsible for loading the Linux kernel and system into memory. LILO can also boot the computer into different operating systems if they are running