users.”
—hitsujiTMO (Reddit Inc.) in
https://www.reddit.com/r/Ubuntu/comments/2yeyyi/grab_your_pitchforks_ubuntu_to_switch_to_systemd/cp92iroYou can manage nearly every aspect of your computer and how it behaves
after booting via configuring and ordering boot scripts and by using various
system administration utilities included with Ubuntu. In this chapter, you
learn how to work with these boot scripts and system administration utilities.
This chapter also offers advice for troubleshooting and fixing problems that
might arise with software configuration or the introduction or removal of
various types of hardware from your system.
Beginning the Boot Loading Process
Although the actual boot loading mechanism for Linux varies on different
hardware platforms (such as SPARC, Alpha, and PowerPC systems), Intel-
based PCs running Ubuntu most often use the same mechanism throughout
product lines. This process is traditionally accomplished through a BIOS. The
BIOS is an application stored in a chip on the motherboard that initializes the
hardware on the motherboard (and often the hardware that’s attached to the
motherboard). The BIOS gets the system ready to load and run the software
that we recognize as the operating system.
As a last step, the BIOS code looks for a special program known as the boot
loader or boot code. The instructions in this little bit of code tell the BIOS
where the Linux kernel is located, how it should be loaded into memory, and
how it should be started.
If all goes well, the BIOS looks for a bootable volume such as a floppy disk,
CD-ROM, hard drive, RAM disk, USB drive, or other media. The bootable
volume contains a special hexadecimal value written to the volume by the
boot loader application (such as Ubuntu’s default, GRUB2) when the boot
loader code was first installed in the system’s drives. The BIOS searches
volumes in the order established by the BIOS settings (for example, USB
first, followed by a DVD-ROM, and then a hard drive) and then boots from
the first bootable volume it finds. Modern BIOSs allow considerable
flexibility in choosing the device used for booting the system.
NOTE
If the BIOS detects a hardware problem, the boot process fails, and the
BIOS generates a few beeps from the system speaker. These “beep codes”
indicate the nature of the problem the BIOS has encountered. The codes