Linux_book

Question 1

What is the distinction between free software and open source software given by Richard
Stallman, the founder of the free software movement?

Answer 1

Open source is a development methodology; free software is a social movement. Free software refers to
freedom rather than to software that has no cost associated with it.

Question 2

What is one of the main advantages of Linux that has enabled it to be applied to many
different computing roles?

Answer 2

Linux is highly extensible, which makes it an excellent choice for computing roles as diverse as servers,
workstations, mainframes, and mobile devices.

Question 3

True or false? There is a single Linux master distribution from which all other Linux distributions
are derived.

Answer 3

False. There is no single master Linux distribution. There are several top-level (not derived from another
distribution) distributions from which others are derived. Slackware, Debian, and Red Hat Enterprise Linux
are examples of top-level distributions.

Question 4

Which Unix philosophy states that developers should create software that is limited in
functionality because it’s easier to use and to maintain?

Answer 4

Worse is better. The assumption is that limited functionality is worse than creating software that does
everything.

Question 5

Linux incorporates software tools from which of the following sources?

Unix
The GNU Project
Berkeley Software Distribution (BSD)
macOS

Answer 5

The GNU Project

Question 6

Which of the following statements about free and open source
software (FOSS) are true? (Choose two.)

Anyone can access the source code.
The author cannot charge a price for the source code.
Anyone can modify the source code.
The source code can only be distributed to a public developer community.

Answer 6

Anyone can access the source code.

Anyone can modify the source code.

Question 7

Which of the following FOSS licenses is the Linux kernel released
under?

GNU General Public License (GPL) version 2
GNU GPL version 3
MIT License
Apache License 2.0

Answer 7

GNU General Public License (GPL) version 2

Question 8

True or false? Linux distributions can include proprietary software by
default.
True
False

Answer 8

True

Question 9

Which of the following Linux distributions is the no-cost version of Red
Hat Enterprise Linux (RHEL)?
Ubuntu
Fedora
openSUSE
CentOS

Answer 9

CentOS

Question 10

Which of the following characteristics are emphasized by the Unix design
philosophy? (Choose two.)
Modularity
Stability
Complexity
Simplicity

Answer 10

Modularity

Simplicity

Question 11

True or false? Linux is Unix-like in its design.
True
False

Answer 11

True

Question 12

Which of the following computing roles does Linux dominate in market share?
(Choose three.)
Workstations
Web servers
Mobile devices
Supercomputers

Answer 12

Web servers
Mobile devices
Supercomputers

Question 13

True or false? In Linux,

Equipment.txt and equipment.txt refer to the
same file.

Answer 13

False. Linux file names are case-sensitive. These are two different files.

Question 14

Which command enables a user to log in to a system with their own credentials, and then to become the root user to perform administrative tasks?

Answer 14

Su - The su command enables an authorized user to become the root user.

Question 15

A fellow administrator calls you and needs you to check the /etc/shadow file for a new user’s entry, confirming that it indeed exists. How would you look at the contents of the /etc/shadow file without the possibility of changing the file?

Answer 15

1) su – 2) cat /etc/shadow —You first have to become the root user because
the /etc/shadow file can only be read as root. To look at the file without the possibility of
altering its contents, use the cat command to list its contents to the screen.

Question 16

You need to quickly create an empty file (log.txt ) so that an application can copy data into it. Which command can you use to create the file?

Answer 16

touch log.txt

Question 17

You recall that a few days ago, you ran a command that helped you find a filtered list of files on the file system. You don’t remember the command’s somewhat complex syntax. How can you reproduce the command without searching the Internet for the correct syntax again?

Answer 17

Use the Up Arrow key until you find it and then press Enter to execute it. The Up
Arrow key scrolls back, one command at a time, through your command history.

Question 18

Since Linux is generally community (user) supported, name three sources of Linux documentation.

Answer 18

Any three of the following: Manual pages, built-in help commands, online
documentation projects, Usenet newsgroups, Internet mailing lists, question and
answer websites, forums and social media, and books and other print resources.

Question 19

To access complete local documentation, which command can you enter at the command-line to access extensive usage information on the cp (copy) command?

Answer 19

man cp

Question 20

A coworker sends you an instant message and asks you how to appropriately format a manual page for the mv command so that she can send it to the printer and get readable output. What command can she enter?

Answer 20

man –t mv

Question 21

Which online documentation site provides a comprehensive resource for Linux documentation including manual pages, FAQs, HOWTOs, and
other types of documentation?

Answer 21

The Linux Documentation Project (https://www.tldp.org)

Question 22

If you know the name of a command and want to know what its function is, which command would you use to find out?

Answer 22

Whatis

Question 23

Given what you’ve read in the man page for grep so far, answer what you think the following command does: grep -i hello myfile

Answer 23

This command will return any lines in the file myfile that contain the text “hello”,
no matter what case the text is in (case insensitive).

Question 24

Name the three types of Linux user accounts.

Answer 24

Root user (superuser), standard user, and service.

Question 25

You need to add an administrator to the /etc/sudoers file to give them the ability to use the sudo command. Which command must you use to add users to the /etc/sudoers file?

Answer 25

You must use visudo since you cannot edit the /etc/sudoers file directly with Vim or
other text editors.

Question 26

Why is it a security best practice to log onto a Linux system with a regular user account rather than with the root user account?

Answer 26

The primary reason is to prevent harmful mistakes from happening to the system through errant
commands such as rm (remove). Users who can use the sudo command should do so on an
individual command basis to perform necessary tasks with elevated privileges, while remaining in
their user shells for other functions.

Question 27

Why is it important to put the principle of least privilege into practice?

Answer 27

System security is greatly enhanced by only granting users the minimum amount of rights and
permissions they require to perform a task.

Question 28

Describe the difference between using the su command and using the sudo
command to perform administrative tasks.

Answer 28

The su command enables an authorized user to become the root user by switching to the root
user account in a complete root-owned shell. This is handy for the administrator but very dangerous because of the potential for human error. The sudo command enables an authorized user to issue individual commands as the root (or other user), limiting potential damage to the system.

Question 29

In which file are user accounts stored?

Answer 29

/etc/passwd

Question 30

What are the three commands used to properly edit the /etc/passwd file?

Answer 30

useradd, usermod, and userdel

Question 31

In which file are hashed passwords stored?

Answer 31

/etc/shadow

Question 32

Why are /etc/passwd and /etc/shadow different files?

Answer 32

The /etc/passwd file stores user account details such as user names, default shell, home directory, and group names. The /etc/shadow file contains the
hashed passwords that are only readable by the root user account, whereas /etc/passwd is readable by everyone. Having a separate file for each, with different permissions, strengthens security.

Question 33

With which command can you change the default user shell to the KornShell for user bsmith ?

Answer 33

sudo usermod -s /bin/ksh bsmith

Question 34

Why do administrators, classes, and best practices state that you should manage users by managing groups?

Answer 34

Managing groups simplifies user administration. Rather than granting explicit permissions to users on an individual basis, you grant them to groups and add users to those groups.

Question 35

Which file contains the groups and user members of those groups?

Answer 35

/etc/group

Question 36

Which three commands does a system administrator use to properly edit a Linux system’s group file?

Answer 36

groupadd, groupmod, and groupdel

Question 37

Which command does a system administrator use to add a user (bsmith ) to an existing group (finance)?

Answer 37

sudo usermod -aG finance bsmith

Question 38

True or false? The groupmod command is used to change the name of an existing
group.

Answer 38

True.

Question 39

As a Linux administrator, you might often switch accounts from yours to the root user or to other user accounts to perform tasks. Which command can you issue to find out which user account you’re currently using?

Answer 39

Whoami

Question 40

You suspect that a hardware failure is imminent and you need to reboot the system to ensure that everything is working properly or to force a failure. Before issuing the reboot command, which command can you use to check to see if other users are logged onto the system?

Answer 40

Who

Question 41

A user reports that she was working on an important script when the system rebooted at approximately 6:30 P.M. last night. No warning was given. How can
you find out who was logged into the system at that time and who could have rebooted the system without warning?

Answer 41

The last command will inform you as to who was logged into the system. If an administrator
rebooted the system, you’ll be able to identify him or her from the entries displayed. If the system
crashed, last will also provide that information. Further investigation of systems logs may be
required in the event of a crash.

Question 42

As a system administrator, why might you issue the id command?

Answer 42

The id command displays group information at a glance in an easy-to-read format.

Question 43

As an administrator, you might need to reboot a system or otherwise perform maintenance. Which command would you issue to not only view logged on users
but also their current activity?

Answer 43

The w command displays idle time and the amount of CPU time consumed by user-owned processes. This information will tell you if it’s safe to reboot a system or if you should ask users to log off first.

Question 44

True or false? Using a dot at the beginning of a file name makes the file more secure.

Answer 44

False. The file is hidden from normal view as a matter of organization, but does nothing for
security.

Question 45

What is the primary difference between the .bashrc and the .bash_profile files?

Answer 45

The .bash_profile file is executed upon first login to the system, and .bashrc is executed upon subsequent logins.

Question 46

Which directory’s contents are copied to the user’s home directory upon account creation?

Answer 46

/etc/skel

Question 47

Which file forces system-wide customizations for all users on a system that a user cannot change?

Answer 47

/etc/profile

Question 48

Where should administrators set system-wide variables on a Linux system rather than editing the /etc/profile file directly?

Answer 48

In scripts within the /etc/profile.d directory.

Question 49

Multiple users have complained about file access in a shared directory, but you’ve checked your daily backup reports and there are no corrupt files.
Which command can you issue in the directory in question to
investigate the problem further?

Answer 49

ls -l —This command displays the permissions of all files in the directory to
help you sort out the problem. It’s likely that the directory’s group permissions are
incorrectly set.

Question 50

A group of system administrators were discussing file permissions and decided that setting a particular root-owned text file to read-only for everyone is a best practice. What do the permissions for this file look like?

Answer 50

Either 664 or rw-rw-r– is correct.

Question 51

A user cannot execute a script (collect.sh ) she created and has sent you the contents of the script via email to inspect. After looking at the script, you determine the script is correctly written but permissions are the problem. What command can you issue to adjust the file’s permissions as necessary?

Answer 51

chmod u+x collect.sh

Question 52

A user changed the permissions of a script (myscript.sh ) in a shared directory. The user is curious why everyone can execute the script if the user owns the script and everyone else only has read access. To make the script executable, what command did the user mistakenly issue?

Answer 52

chmod +x myscript.sh —The permissions changed to rwxrwxr-x or 775, which gives everyone execute permission. To limit execute permission to the user and group only, the command should have been:

chmod ug+x myscript.sh

Question 53

Your team lead is tired of receiving help desk tickets to restore deleted files from a directory that contains hundreds of files and subdirectories. She decides to have you fix the problem by making all of the files read-only. How do you change all the files to read-only without having to traverse each directory?

Answer 53

chmod -R 644 *

—This command changes all files in the current directory to 644 recursively.

Question 54

A user (Bob Smith—username: bsmith ) calls you to request that you restore a group of files he accidentally deleted from his home directory. You copy the files for him but he later complains that he can no longer edit the files. What do you need to do so that he can edit his files?

Answer 54

You need to change ownership of the files to him. Change user and group ownership recursively
so that Bob owns all files and directories.

For example: sudo chown -R bsmith:bsmith *

Question 55

Gina wants to share some marketing files with two other members of her team but doesn’t want them to access those files in her home directory. She also wants the directory and its files to only be available to the Marketing group. What steps can you take as an administrator to accomplish this request?

Answer 55

1) You need to create a new group (mkt): sudo groupadd mkt

2) Add users to the
group: sudo usermod -aG mkt gina linda mark

3) Create the shared directory: sudo mkdir /opt/marketing

4) Change group ownership to mkt:
sudo chgrp mkt /opt/marketing

5) Change permissions so that the Marketing
group has full control of the directory and its contents and remove everyone else: sudo
chmod 770 /opt/marketing

Question 56

What command is equivalent to issuing chown :mygrp file1 ?

Answer 56

chgrp mygrp file1

—Both commands change the file’s group to mygrp without changing the owner.

Question 57

As an administrator, you’ve created a shared directory and made the necessary permissions changes to allow a group of users access to that directory. You’ve also added users to the group. When a user (susan ) who is a member of the group creates a file in the shared directory, what user and group permissions will the new file have?

Answer 57

The file’s user and group ownership will both be susan.

Question 58

What must a user do in a shared directory to ensure that each group member has full read and write access to files they create?

Answer 58

Change the group ownership to the group:

chgrp accounting salaries.txt —

The user doesn’t have to be root or use sudo to change group ownership because the file creator is the file’s user and group owner, and therefore may change its permissions at will.

Question 59

The Marketing manager contacts you stating that the shared directory you set up for the Marketing group ( /opt/marketing ) works, but not exactly like they’d planned. When one of the group members creates a file in the directory, the file takes on the user’s user and group permissions.

For
example, when Linda creates a new file, the permissions are

–rwrw-r– linda linda .

The manager wants the files to all retain the mkt group permission, if possible, rather than having the users change the group themselves. What action can you take to fulfill this request?

Answer 59

sudo chmod -R g+s /opt/marketing

—By setting the SGID on the directory, every file created by anyone in the mkt group will have the mkt group ownership.

Question 60

Gina, a member of the Marketing group, has decided that she wants her files protected so that only she can delete them, although other Marketing group members need to be able to work on and edit the files. What can she do to fix the problem of others deleting her files?

Answer 60

You can show Gina the following command to set the sticky bit on her files:

chmod +t filename.txt —This command also works on directories

Question 61

Ruth has searched for a solution to her problem: A few of her training documents keep getting changed or removed by system administrators removing files that haven’t been accessed in excess of 180 days.

She has found that a file can be made immutable, but she cannot make her own files immutable and needs your assistance. How can you make the files /home/ruth/training1_doc.txt and /home/ruth/training2_doc.txt immutable?

Answer 61

sudo chattr +i /home/ruth/training*_doc.txt

Question 62

A user, John, opened a ticket complaining that he has files in his home directory that he cannot remove, although they are his files and he is the user and group owner. He requests that you remove the files /home/john/billing1.txt , billing2.txt , and summary.txt . However, when you attempt to remove the files, you receive an error that you cannot remove the files as the root user.

What is a possible resolution for John?

Answer 62

You can issue the lsattr command to see if immutable flag has been set on
those files. If it has, you can resolve the problem by removing the immutable flag
and then removing the files:

1) sudo chattr –i /home/john/billing1.txt
2) sudo chattr –i /home/john/billing2.txt
3) sudo chattr –i /home/john/summary.txt
4) sudo rm /home/john/billing1.txt
5) sudo rm /home/john/billing2.txt
6) sudo rm /home/john/summary.txt

Question 63

You created a shared directory for the Marketing planners, Linda and Mark, named /opt/MPlans . Their group, mplan , has exclusive access to this directory. No other user can access the directory or its contents. Linda decides that Gina needs read-only access to a single file, history.txt , inside the /opt/MPlans directory. Is this kind of restrictive access possible? If so, how
can you grant it to Gina?

Answer 63

Yes, it is possible through ACLs. First, grant Gina read and execute access to the directory:

setfacl -m u:gina:rx /opt/MPlans

and then, set read access to the history.txt file inside the MPlans directory:

setfacl -m u:gina:r /opt/MPlans/history.txt

—You can check your work by executing getfacl on the
directory and its contents.

Question 64

Rose Stanley opened a ticket indicating that she is denied the ability to delete a directory. She confirmed with the service desk that she has write permission to the directory. What suggestion would you make to address the issue?

Answer 64

Users also need the execute permission to remove a directory.

Question 65

Jerry Robinson received an access denied message on a file. He told the service desk that the user permissions indicate the owner has read access. What suggestion would you make to address the issue?

Answer 65

Check to see if Jerry Robinson’s account is the owner of the file, and if not, make him the owner if
he should be.

Question 66

Rose Stanley received an access denied message on a file. She used the ls -l command to discover what group had been granted access to the file. She believed she should be able to access the file. What suggestion would you make to address the issue?

Answer 66

Use the id command with Rose Stanley’s account to ensure she is a member of the group
specified by the file’s permissions.

Question 67

Jerry Robinson cannot use the cd command to navigate into a particular directory. He told the service desk that he used ls -l to see what group is associated with the file. He also confirmed that the group is listed as having read access to the directory. He then used the id command to confirm he is a member of that group. What suggestion would you make to address this issue?

Answer 67

Users also need the execute permission to change into a directory.

Question 68

A group with a shared directory set up by another administrator is having several problems with permissions in that directory. You’ve been asked to investigate. Which commands can you use to check existing permissions to help assess the current setup?

Answer 68

1) ls -al
2) getfacl
3) lsattr

—These commands will give you a good perspective on
permissions, ACLs, and any attributes that have been set on the shared directory and files.

Question 69

A user complains that a script that she created and has full access to (rwxrwx— ) is not executing for her. What is the problem with this script?

Answer 69

The execute bit was removed from the script by the ACL. It’s possible that the script consumed
too many resources and an administrator likely removed execute access to it.

Question 70

Bob opens a ticket stating that he receives a permission denied error when trying to cd into /opt/Finance . Bob is a member of the FinanceDept group. What is the problem with Bob’s access?

Answer 70

While Bob is part of the FinanceDept group and can access all other FinanceDept group assets, he cannot use /opt/Finance because he doesn’t have access via ACLs to that directory.