Linux with Operating System Concepts

Directory
Use
Subdirectories (If Any)
/bin
User executable programs
None
/boot
Linux boot programs including boot loader 
program (grub in most cases)
Boot loaders in subdirectories
/dev
Physical devices are treated as files, stored in 
this directory
Various to organize specific types of devices, 
see Table 3.10
/etc
Configuration files and scripts
Numerous
/home
User home directory space
One subdirectory per user
/lib
Libraries used by the kernel and programs 
stored in /bin, /sbin
modules, security, udev, etc
/lost
+
found
Recovered files from disk errors due to an 
unexpected shutdown of the system
None
/media
Initially empty, removable media can be 
mounted here
None
/mnt
Mount point for temporary file systems
None
/opt
Initially empty, this optional directory can be 
used to install some application software
Application software subdirectories (if any)
/proc
Kernel records of running process 
information
Subdirectories created dynamically of each 
running process
/root
The system administrator’s home directory
None, or subdirectories for profile storage 
such as .config, .gconf, .mozilla
/sbin
Like /bin, system executable programs, but 
these are typically used by system 
administrators, not users
None
/tmp
Temporary storage for running processes
None initially
/usr
Application software files and executables
bin, etc, include, lib, local, sbin, share, src, 
tmp
/var
Data files that grow over time (printer spool 
files, email repositories, log files, etc.)
Varies by system, includes cache, log, mail, 
spool, www

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Navigating the Linux File System
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107
3.7 SECONDARY STORAGE DEVICES
Let us focus on secondary storage devices to get a better idea of what they are and how 
they operate. Storage devices differ from main memory in three ways. First, we use stor-
age devices for permanent storage whereas main memory is used to store the program 
code and data that the processor is using, has used recently or will use in the near future. 
Second, storage devices are usually nonvolatile forms of storage meaning that they can 
retain their contents even after the power has been shut off. This is not the case with main 
memory (DRAM), cache or registers, all of which are volatile. Third, storage devices have 
a far greater storage capacity than main memory. The amount per byte of storage for hard 
disk is extremely cheap when compared to that of DRAM. On the other hand, DRAM 
access time is far shorter than hard disk access time.
There are several different technologies used for storage devices. The primary form is the 
hard disk drive. There are also optical disk drives, magnetic tape, solid-state drives (SSD, 
including flash memory drives) and in the case of older computers, floppy disk drives. 
Each of these technologies stores information on a physical medium that is separate from 
the device that accesses the information. In the case of the floppy disk, optical disk and 
magnetic tape, the media is removable from the device. In the case of the hard disk drive, 
the disk platters are permanently sealed inside the disk drive. Finally, the USB drive is 
removable from the computer where it is inserted into a USB port. Table 3.11 illustrates 
differences between these devices.
TABLE 3.10 
Common/dev Devices