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For example, if you
had three SCSI hard drives in your system, a single instance of the SCSI kernel driver can
manage the three physically separate devices.
CHAPTER 18 Managing Files, Volumes, and Drives 400
The Linux kernel keeps track of these different devices using major and minor device
numbers. These numbers are assigned to each device??™s associated file in /dev. The major
number indicates the type of device associated with the file. For example, consider the
files displayed in Figure 18.20.
FIGURE 18.20 Major and minor numbers.
In Figure 18.20, the ls -l command has been used to display the various IDE device files
in /dev, denoted as hda. Notice in the middle of each line in the output of ls that two
numbers are displayed. The first number is the major number. All IDE devices have a
major number of 3. (SCSI devices have a major number of 8.) The major number identifies
which device driver the kernel should use to interface with the particular device.
You will also see a second number listed in the middle of each line of the output of ls.


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