101 System Architecture
101.1 Determine and Configure hardware settings
101.2 Boot the System
101.3 Change runlevels and shutdown or reboot system
All OSs run atop hardware, and this hardware influences how the OSs run. Most obviously, hardware can be fast or slow, reliable or unreliable. Somewhat more subtly, OSs provide various means of configuring and accessing the hardware—partitioning hard disks and reading data from Universal Serial Bus (USB) devices, for instance. You must understand at least the basics of how Linux interacts with its hardware environment in order to effectively administer a Linux system, so this chapter presents that information. This chapter begins with a look at firmware, which is the lowest-level software that runs on a computer. A computer’s firmware begins the boot process and configures certain hardware devices. This chapter then moves on to expansion cards and USB devices. This chapter concludes with an examination of disk hardware and the filesystems it contains—disk interface standards, disk partitioning, how to track disk usage, how to tune filesystems for optimal performance, how to check filesystems’ internal consistency, and how to repair simple filesystem defects. Assuming a filesystem is in good shape, you must be able to mount it to be able to use it, so that topic is also covered here. (One disk topic, boot managers, is covered in Chapter 5, “Booting Linux and Editing Files.”)