Linux with Operating System Concepts

faculty
has sudo access to the killall command. You, a faculty 
member, want to kill all copies of the process 
someprocess
. What command would 
you issue using sudo?
44. Why should you use visudo to modify the /etc/sudoers file rather than directly edit-
ing it in vi?
45. Aside from the examples covered in Section 9.7, name three additional examples of 
why you might set up sudo privileges for one or more users.
Assume you are the sole system administrator for a small company of 10–20 users. Your 
organization has a single file server that primarily stores software and group documents. 
User documents can either be stored on the file server or, more often, user workstations. 
The company currently has no restrictions placed on users in terms of personal use of 

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company computers. Answer questions 46–49 regarding user account policies for this 
organization. Offer a brief explanation to each answer.
46. Should there be a policy prohibiting users from downloading software on their 
workstations?
47. Should users have quotas placed on their file server space should they decide to store 
files there?
48. Should the company install a proxy server to store commonly accessed web pages and 
also use it to restrict access to websites deemed unrelated to company business?
49. Should users be able to access the file server from off-site computers?
You have been asked to propose user account policies for a large company of 250 employ-
ees. The company utilizes file servers to store all user files. In addition, the company has 
its own web server and proxy server. Employees are permitted to have their own websites 
if they desire them. The company has a policy restricting computer usage to “professional 
business” only. Answer questions 50–53. Offer a brief explanation to each answer.
50. Should users have disk quotas placed on them for either their file server space or web 
space?
51. Should you establish rules that prohibit certain types of content from employee 
websites?
52. Should the proxy server be set up to restrict access to websites such as Facebook and 
personal email servers (e.g., Gmail, Yahoo mail)?
53. Should the system administrator be allowed to examine individual employee storage 
to see if they are storing information that is not related to the business?
54. As a system administrator, describe a policy that you would suggest for enforcing 
strong passwords (e.g., minimum length, restriction on types of characters used, and 
duration until passwords need to be changed).
55. If you were the system administrator for a university, would you recommend that 
students, once graduated, can keep their accounts? If so, for how long? 6 months? 1 
year? Forever?
56. Repeat #55 assuming you are the system administrator for a corporation of thou-
sands of employees.
57. Repeat #55 assuming it is a small company of 50 employees.

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C h a p t e r
10
The Linux File System
T
his chapter’s learning objectives are
• To understand the types of objects that Linux treats as files and how they differ
• To understand the role of the inode
• To be able to utilize Linux file system commands of badblocks, cpio, df, du, dump, 
mkfifo, mount, stat, umount, and tar
• To understand common partitions in Linux, the role of the files /etc/fstab and /etc/
mtab and the meaning of the term “file system”
• To be able to establish disk quotas
• To understand the role of the top-level Linux directories
10.1 INTRODUCTION
In Chapter 3, we viewed the Linux file system from a user’s perspective. Here, we examine 
the Linux file system from a system administration point of view. For a single user of a 
standalone workstation, there are few duties that the system administrator will be required 
to perform. However, it is still important to understand the concepts of the file system. 
These concepts include partitions, file layout, and the role of the top-level directories. The 
system administrator for a larger Linux system or a network of workstations will have to 
monitor file system usage and performance, perform backups, and handle other duties.
This chapter breaks the Linux file system into four basic topics. First, we examine a file. 
For this, we consider what types of entities make up files in the file system. We will find 
that in Linux many types of entities are treated as files. This lets us apply file operations 
to any or all of them. By examining the storage structure of a file through the inode, we 
can see how files are stored. Second, we examine the partition. We discussed the role of 
partitioning during the Linux installation in Chapter 8. Now we look at what a partition 
is, why we partition our file space, how to handle a partition, and how to repartition the 

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Linux with Operating System Concepts
file system. Third, we look at the top-level directories. Although we briefly examined this 
layout in Chapter 3, here we focus on them in more detail, spotlighting the more important 
directories, subdirectories, and files of note. Finally, we look at some administrative duties 
to support a secure and reliable file system. Before we examine the specifics of the Linux 
file system, we will first consider a generic file system.
10.2 STORAGE ACCESS
A collection of storage devices present a file space. This file space exists at two levels: a 
logical level defined by partitions, directories, and files, and a physical level defined by file 
systems, disk blocks, and pointers. The users and system administrators primarily view the 
file space at the logical level. The physical level is one that the operating system handles for 
us based on our commands (requests).
The devices that make up the file space include hard disk drives, optical disk drives 
and optical disks, solid-state drives, including USB drives, and in some cases magnetic 
tape drives and magnetic tape media. In some cases, storage is shifted into memory in the 
form of ramdisks or other mechanisms whereby memory mimics file storage. Ramdisks 
are discussed in Section 10.5 when we examine some of the devices found under /dev. 
Collectively, these devices provide us with storage access, where we store executable pro-
grams and data files. We generally perform one of two operations on this storage space: we 
read from a file (load the file into memory, or input from file) and we write to a file (store/
save information to a file, or output to file).
10.2.1 Disk Storage and Blocks
As hard disk storage is the most common implementation of a file system, we will con-
centrate on it although some of the concepts apply to other forms of storage as well. To 
store a file on disk, the file is decomposed into fixed-sized units called 
blocks
. Figure 10.1 
illustrates a small file (six blocks) and the physical locations of those blocks. Notice that the 
last block may not fill up the entire disk block space, so it leaves behind a small