7 File System

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The Linux Filesystem

Terms youll need to understand:

mknod

fdisk

mkfs

df

du

fsck

Inode

ln

mount

umount

quotaon

quotaoff

edquota

repquota

Quota

quotacheck

quotastats

locate

updatedb

which

find

xargs

Techniques youll need to master:

Understanding how the standard

Linux directories are arranged andthe purpose for each

Recognizing the core utilities used

for interaction with the disk

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2Chapter 7

In this chapter, youll learn of the standard disk layout and the utilities used to

manage and alter disks. Directories, subdirectories, and files have been major

topics throughout this book, and now it is time to elaborate on them by discuss-

ing the purpose and default content of each.

The Standard Disk LayoutThe Linux installation created a number of directories to hold system files. Any

normal installation, regardless of the vendor, creates the file structure depicted in

Figure 7.1.

The following sections discuss each of the directories.

The / directoryEverything begins at the root directory (/).The root is the directory from which

everything else becomes a subdirectory or subcomponent. When specifying loca-

tions using absolute addressing, you always begin with this directory because it is

the ultimate origin, and it is impossible to move any further back since there is no

directory above it.

The bin directoryThe bin directory holds the binaries (executables) that are essential to using the

Linux operating system. Many of the utilities discussed so far are located in thebin directory, including:

cat

cp

date

ls

mkdir

mv

ps

sed

As a rule of thumb, the executable or binary files located within this directory

are available to all users. Binary files that are not critical to the operation of

the system, or that are needed by all users, commonly appear in /usr/bin in-

stead of here.

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35The Linux Filesystem

Practice Questions

Question 1

Which file updates the database that the locate command uses to find

matches for search names?

a. locatedb

b. fstab

c. mtab

d. updatedb

The correct answer to this question is d. Theupdatedbutility updates the data-

base. Answer a is the name of the database thelocateutility uses to find the files,

so it is incorrect. Answer b is the file system table, and answer c is the mount

table, neither of which relate to the locate utility.

Question 2

Which of the following files would be read by the commandmount -a? a. /etc/mtab

b. /etc/fstab

c. /etc/update.conf

d. /etc/mount

The correct answer to this question is b. The fstab file holds information about

the filesystems known to it. Answer a/etc/mtabis where entries are written

when the filesystems are loaded, so it is incorrect. The other two choices are

invalid in relation to the question.

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36 Chapter 7

Question 3

You want to start using quotas on the third partition of your systems disk. To

begin, you must edit the fstab file. To which field must you add theusrquota

entry?

a. First

b. Second

c. Third

d. Fourth

e. Fifth

f. Sixth

The correct answer to this question is d. You must add the entry to the fourth

field of the entry for the quotas to be invoked.

Question 4

What is the syntax to use to create a symbolic link named advise to a file

in the same directory named please? [Fill in the blank]

_______________

The correct answer to this question is:

l n - s pl ease advi se

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Question 5

Which of the following locations could contain the kernel? [Check all cor-

rect answers]

a. /

b. /bin

c. /boot

d. /etc

The correct answers to this question are a and c. The default location for the

kernel, which differs according to vendors and versions, is either root (/) or /boot.

The /bin directory (choice b) holds executable files for all users, while the /etc

directory (choice d) is used to hold configuration files; hence, these two choices

are incorrect.

Question 6

Which of the following options can you use with the findutility to prompt a

user before carrying out an operation?

a. -exec b. -query

c. -ok

d. -perm

The correct answer to this question is c, which prompts you before carrying out

an action. Answer a executes the same operation without first prompting the

user; answer b is not an option for find; and answer d locates only files that meet

the specified permissions.

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38 Chapter 7

Question 7

You are getting ready to begin system-administration tasks on your system.

Before starting anything, you want to compile a list of utilities that are avail-

able only for this purpose (adding users, groups, and so on). Which directory

contains the entries you are seeking?

a. /usr/sbin

b. /usr/bin

c. /sbin

d. /bin

The correct answer to this question is a. The /usr/sbin directory holds system-

specific administrative binaries for use by the administrator. Answer b is used by

all users, so it is incorrect. Answer c holds system utilities, but most are available

for system purposes other than adding users and groups, such as formatting, check-

ing the file systems, and so on; therefore, it is incorrect. Answer d is used by all

users, so it is incorrect.

Question 8

On a SCSI hard drive, which of the following indicates the third partition on

the second disk?

a. hba3

b. sba3

c. sdb3

d. hdc2

The correct answer to this question is c. Thesindicates the type of disk, which is

SCSI; thed indicates the type of device, which is disk; theb indicates the second

disk; and the3 indicates the third partition.

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Question 9

Which utility can you use to format a partition?

a. format

b. fdisk

c. mkfs

d. mount

The correct answer to this question is c. You use themkfsutility to format apartition. Answer a does not exist in L inux, so it is incorrect. Answer b, fdisk,

creates partitions, so it is incorrect. And answer d is used to load a remote filesystem,

so it is incorrect.

Question 10

Thefsck utility has found a number of corrupted files, and you have chosen

to correct the filesystem. To which directory are the corrupted files written?

a. lost+found

b. tmp

c. etc

d. /

The correct answer to this question is a. The /lost+found directory holds the

corrupted files. Usually they are so corrupted that their names are no longer known,

and thus the files are written here by inode number. The /tmp directory (answer

b) holds temporary files that do not need to survive a reboot. The /etc directory

(answer c) hold configuration files used by the system, while the root directory

(answer d) is the starting point of all subdirectories.

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40 Chapter 7

Need to Know More?/usr/src/linux/Documentation/devices.txt describes many of the en-

tries in the /dev directory.

www.linuxdoc.org/HOWTO/mini/Quota.html defines quotas and

explains their requirements within Linux. The site addresses setup and

configuration details, as well as corresponding utilities.

www.linuxdoc.org/HOWTO/Filesystems-HOWTO.html is not

specifically limited to L inux (it includes NT FS and other filesystems),

but it fully explains the Extended Filesystems (ext2 and so on) in the

sixth section of the document.

@@@insert documentation icon??? is this the same

as the book icon?????@@@

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