Linux with Operating System Concepts

Name
Description
autofs
File system
cdrom, cdrw
CD drives
core
A link to the proc directory of a file that represents memory
cpu
CPU register information
dvd, dvdrw
DVD drives
fd0, fd1, …
Floppy disk drives
input
A directory that contains event devices, events are generated by input devices
hda0, hda1, …
IDE-style hard drives
loop0, loop1, …
Mounted devices not accounted for by other device names (e.g., cdrom, dvd, usb)
lp0, lp1, …
Printers
net
Network interface
null
Discards anything sent to it (used like a trash can)
ppp
Point-to-point network devices
ram0, ram1, …
Ramdisks
random
Generates a random number
sda0, sda1, …
SCSI and SATA-style hard drives
tty0, tty1, …
Terminal windows
usb
For USB compatible devices
zero
Produces the value 0 for processes that need it

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Linux with Operating System Concepts
3.7.1 The Hard Disk Drive
*
The hard disk drive is the most common form of secondary storage. Every laptop and 
desktop computer will come with an internal hard disk drive. In most cases, the operating 
system will be stored here (there are exceptions such as using a USB or optical disk to live 
boot Linux). Additionally, the user(s) of the computer will most likely install all software 
and store all data files onto this drive. Alternatively, some data files may be saved on other 
drives such as an external hard disk or optical disk.
The hard disk drive is a self-contained unit that combines the media storing the files 
with the technology to read and write data to the media. The media are several platters 
of “hard” disks. The disk drive unit also contains a spindle to spin the platters, two read/
write heads for each platter (one above, one below) and the circuitry to move the read/write 
heads and perform the disk access. The surface of the hard disk is broken into logical seg-
ments called tracks and sectors. This segmentation is performed during disk formatting. 
See Figure 3.9 for an illustration of the hard disk drive.
Hard disk drives spin their disks very rapidly (up to 15,000 revolutions per minute) and 
have a high transfer rate (higher than all other storage devices) although far lower than 
the access time of DRAM. The hard disk drive is sealed so that the environment (dust, 
particles of food, hair, etc.) cannot interact with the disk surface. The hard disk drive uses 
a form of magnetic storage. Information is placed onto the surface of the disk as a sequence 
of magnetized spots, called magnetic domains or magnetic moments. These magnetized 
domains correspond to the magnetization of the atoms of the region. One magnetized spot 
is denoted with these atoms being aligned in one of two directions. We can refer to the two 
*
Transfer rate, common size, and common cost are based on values available in October 2013. These values tend to change 
frequently.
TABLE 3.11 
Characteristics of Storage Devices*