Device Drivers

A Sun computer typically uses a wide range of peripheral and mass-storage devices such as a SCSI disk drive, a keyboard and a mouse, and some kind of magnetic backup medium. Other commonly used devices include CD-ROM drives, printers, and various USB devices. Solaris communicates with peripheral devices through files called device files or drivers. A device driver is a low-level program that enables the kernel to communicate with a specific piece of hardware. The driver serves as the operating system’s “interpreter” for that piece of hardware. Before Solaris can communicate with a device, the device must have a device driver.

When a system is started for the first time, the kernel creates a device hierarchy to represent all the devices connected to the system. This is the autoconfiguration process, which is described later in this chapter. If a driver is not loaded for a particular peripheral, that device is not functional. In Solaris, each disk device is described in three ways, using three distinct naming conventions:

• Physical device name Represents the full device pathname in the device information hierarchy.

• Instance name Represents the kernel’s abbreviation name for every possible device on the system.

• Logical device name Used by system administrators with most file system commands to refer to devices.

System administrators need to understand these device names when using commands to manage disks and file systems. We will discuss these device names throughout this chapter.