Practice Free 010-160 Linux Essentials Certificate Exam - version 1.6 Exam Questions Answers With Explanation

 A typical shell script is a text file that contains a series of commands or instructions that can be executed by a shell interpreter. A shell script usually has the executable permission bit set, which means that it can be run as a program by the user or another program. A shell script also starts with the two character sequence #!, which is called a shebang or a hashbang. This sequence tells the operating system which shell interpreter to use to run the script. For example, #!/bin/bash indicates that the script should be run by the bash shell. References:

• Linux Essentials - Linux Professional Institute (LPI) 1
• Linux Essentials - Linux Professional Institute Certification Programs 2

The correct command to change the ownership of the file doku.odt to a new owner named tux is chown tux doku.odt. This command uses the chown command, which stands for change owner, followed by the name of the new owner and the name of the file as arguments. The chown command allows you to change the user and/or group ownership of a given file, directory, or symbolic link12. The other options are incorrect because they use different commands or syntax that do not change the ownership of the file. For example:

• Option A uses the chmod command, which stands for change mode, and is used to change the permissions of files and directories, not the ownership3.
• Option B uses the newuser command, which is used to create a new user account, not to change the ownership of a file4.
• Option D uses the transfer command, which is not a valid Linux command.
• Option E uses the passwd command, which is used to change the password of a user account, not the ownership of a file5.

References: 1: Chown Command in Linux (File Ownership) | Linuxize 2: chown command in Linux with Examples - GeeksforGeeks 3: Chmod Command in Linux (File Permissions) | Linuxize 4: newusers(8) - Linux man page 5: passwd(1) - Linux man page

 A bus is a communication system that transfers data between components inside a computer or between computers. There are different types of buses that serve different purposes. The RAM bus connects the CPU with the main memory, the NUMA bus connects multiple processors in a multiprocessor system, the CPU bus connects the CPU with other components on the motherboard, and the Auto bus is a fictional bus that can transform into a robot. The SATA bus is the correct answer because it is a type of bus that can connect hard disk drives with the motherboard. SATA stands for Serial Advanced Technology Attachment and it is a standard interface for connecting storage devices such as hard disk drives, solid state drives, and optical drives. SATA offers faster data transfer rates, lower power consumption, and improved cable management compared to older interfaces such as IDE and SCSI. References: : [Bus (computing)] : [Transformers: Robots in Disguise (2015 TV series)] : [Serial ATA]3) : [SATA vs. IDE: What’s the Difference?]

The tar command in Linux is used to create, extract, list, and manipulate archive files1. The -c option tells the command to create a new archive file. The -f option specifies the name of the archive file. The last argument is the name of the directory or file to be archived. Therefore, the command tar -cf work.tar ./work/ will create an archive file named work.tar from the contents of the directory ./work/. The other options are either invalid or do not create the desired archive file. Option A uses an unrecognized option --new. Option C uses an incorrect option --content and an incorrect extension .tgz for a plain tar archive. Option D and E use an incorrect syntax for redirecting the input or output of the tar command. References:

• Linux Essentials Version 1.6 Objectives, Topic 1.4: Command Line Basics, Subtopic: Basic Shell Commands
• Linux Essentials Version 1.6 Exam Preparation Guide, Section 1.4: Command Line Basics, Page 16
• Tar Command in Linux (Create and Extract Archives) | Linuxize2

 The reason why the script.sh does not display the content of the variable MYVAR is that the variable is not exported to the environment of the script. When a script is executed, it runs in a separate process that inherits the environment variables from the parent process, but not the shell variables. A shell variable is a variable that is defined and visible only in the current shell session, while an environment variable is a variable that is exported to the environment and visible to all processes that run in that environment1.

To make a shell variable an environment variable, we need to use the export command. The export command takes a shell variable name and adds it to the environment of the current shell and any subshells or processes that are created from it2. For example, to export the variable MYVAR with the value value, we can use:

export MYVAR=value

This will make the variable MYVAR available to the script.sh when it is executed, and the script will print the value of MYVAR as expected. Alternatively, we can also use the export command with the -n option to remove a variable from the environment, or with the -p option to list all the environment variables2.

The other options are not valid ways to set MYVAR as an environment variable. The !MYVAR=value option is not a valid syntax for setting a variable in bash. The env MYVAR=value option will run the env command with the MYVAR=value argument, which will print the environment variables with the addition of MYVAR=value, but it will not affect the current shell or the script.sh3. The MYVAR=value option will set MYVAR as a shell variable, but not as an environment variable, so it will not be visible to the script.sh1. The $MYVAR=value option will try to set the variable whose name is the value of MYVAR to the value value, which is not what we want4. References:

• Linux Essentials Exam Objectives, Version 1.6, Topic 103.1, Weight 2
• Linux Essentials Certification Guide, Chapter 3, Page 51-52
• env(1) - Linux manual page
• Bash Variables - LinuxConfig.org

The /etc/skel directory is a skeleton directory that contains the default files and directories that are automatically copied to the home directory of a new user when the account is created by the useradd command12. The purpose of this directory is to provide a consistent and uniform environment for all new users and to save the system administrator’s time and effort in configuring the user settings12. The /etc/skel directory can be customized by adding or removing files and directories as needed, depending on the desired default settings for the new users12.

The other options are incorrect because:

• A. The personal user settings of root are stored in this directory. This is not true, as the personal user settings of root are stored in the /root directory, which is the home directory of the root user3. The /etc/skel directory does not affect the root user’s settings, but only the settings of the new users created by the useradd command12.
• B. The files from the directory are copied to the home directory of the new user when starting the system. This is not true, as the files from the directory are copied to the home directory of the new user when the account is created, not when starting the system12. The copying process only happens once, when the useradd command is executed, and not every time the system is started12.
• E. The directory contains the global settings for the Linux system. This is not true, as the directory contains the default settings for the new users, not the global settings for theLinux system12. The global settings for the Linux system are usually stored in other directories under /etc, such as /etc/default, /etc/sysconfig, /etc/init.d, etc4.

References:

• Understanding the /etc/skel directory in Linux – The Geek Diary
• /etc/skel directory in Linux - techPiezo
• Linux File System Hierarchy - /root directory - LinuxConfig.org
• Linux configuration: Understanding *.d directories in /etc | Enable Sysadmin

A Linux distribution is a collection of software that is based on the Linux kernel and can be installed on a computer or a device to create a functional operating system. A Linux distribution typically includes the Linux kernel, a set of system utilities and libraries, a graphical user interface (GUI), a package manager, and various applications and services. A Linux distribution may also include additional software or features that are specific to the distribution’s goals, target audience, or philosophy. For example, some Linux distributions are designed for desktop users, while others are optimized for servers, embedded systems, or security. Some Linux distributions are based on other Linux distributions, while others are developed independently. Some Linux distributions are free and open source, while others are proprietary or commercial. Some Linux distributions are popular and widely used, while others are niche or experimental. Some examples of Linux distributions are Ubuntu, Fedora, Debian, Mint, Arch, and Red Hat. References:

• Linux Essentials Topic 101: System Architecture, section 101.1: Determine and configure hardware settings.
• Linux Essentials Topic 102: Linux Installation and Package Management, section 102.1: Design hard disk layout.
• Linux Essentials Topic 103: GNU and Unix Commands, section 103.1: Work on the command line.
• Linux Essentials Topic 104: The Linux Operating System, section 104.1: Boot the system.
• Linux Essentials Topic 105: The Power of the Command Line, section 105.1: Use text streams and filters.
• Linux Essentials Topic 106: Security and File Permissions, section 106.3: Modify file and directory permissions.
• What is a Linux distribution? - Linux.com
• Linux distribution - Wikipedia
• Best Linux Distributions For Everyone in 2023 - It’s FOSS

 A private web browser window is a mode of browsing that prevents the browser from saving your browsing history, cookies, and other site data, or information entered in forms. However, it does not prevent websites, your employer or school, or your internet service provider from tracking your online activity. The main differences between a private web browser window and a regular web browser window are:

• Private web browser windows do not store cookies persistently. Cookies are small files that websites use to store information on your device, such as your preferences, login status, or tracking data. In a regular web browser window, cookies are stored until they expire or you delete them. In a private web browser window, cookies are deleted when you close all private windows.
• Private web browser windows do not keep records in the browser history. The browser history is a list of web pages that you have visited in the past. In a regular web browser window, the browser history is saved and can be accessed by anyone who uses the same device or profile. In a private web browser window, the browser history is not saved and cannot be viewed by anyone.
• Private web browser windows do not send regular stored cookies. When you visit a website in a regular web browser window, the browser sends any cookies that are stored for that website. This allows the website to recognize you and provide personalized content or services. When you visit a website in a private web browser window, the browser does not send any cookies that are stored in regular windows. This prevents the website from identifying you or linking your activity across different sessions.

References: Browse in private - Computer - Google Chrome Help, Browse InPrivate in Microsoft Edge - Microsoft Support, Private Browsing: What Is It and How to Use It | Edge Learning Center

The command ls …/Documents/ lists the contents of the directory /home/user/Documents/. The reason is that the argument …/Documents/ is a relative path that refers to the parent directory of the current directory, which is /home/user/, followed by the subdirectory Documents/. The ls command displays the files and directories in the specified path, or the current directory if no path is given. The command does not change the current directory, so the user remains in /home/user/Downloads/. References:

• Linux Essentials Exam Objectives, Version 1.6, Topic 103.1, Weight 2
• Linux Essentials Certification Guide, Chapter 3, Page 49-50
• Ls Command in Linux (List Files and Directories) | Linuxize

When a user account is deleted, the files owned by that user are not automatically deleted from the file system, unless they are in the user’s home directory. The files residing outside the home directory will remain unchanged, but they will have an invalid owner. The owner of a file is identified by a numeric user ID (UID), which is mapped to a user name by the /etc/passwd file. When a user is deleted, the corresponding entry in the /etc/passwd file is removed, but the UID of the file is not changed. Therefore, when listing the file’s details, the UID of the former owner is shown instead of the user name. For example, if the user alice with UID 1001 is deleted, and she owns a file named report.txt in the /tmp directory, the output of ls -l /tmp/report.txt will look something like this:

-rw-r–r-- 1 1001 users 1024 Nov 20 14:11 /tmp/report.txt

The user root is not set as the new owner of the file, nor is the file moved to /lost+found or removed from the file system. The /lost+found directory is used to store files that are recovered from a corrupted file system after running the fsck command, not from deleted user accounts. The file system check does not affect the ownership or permissions of the files, unless there is a serious inconsistency that needs to be fixed. References:

• Linux Essentials - Linux Professional Institute (LPI), section 5.2.1
• 5.2 Lesson 1 - Linux Professional Institute Certification Programs, slide 6.

Section: (none)

 The correct device name that represents a hard disk partition is /dev/sda2. This device name follows the Linux convention for naming hard disk devices and partitions. According to this convention123:

• The first part of the device name indicates the type of the device. For example, /dev/hd* for IDE drives, /dev/sd* for SCSI, SATA, USB, or eSATA drives, /dev/nvme* for NVMe drives, etc.
• The second part of the device name indicates the order of the device as detected by the system. For example, /dev/sda is the first serial drive, /dev/sdb is the second serial drive, and so on.
• The third part of the device name indicates the number of the partition on the device. For example, /dev/sda1 is the first partition on the first serial drive, /dev/sda2 is the second partition on the first serial drive, and so on.

Therefore, /dev/sda2 means the second partition on the first serial drive, which is a valid hard disk partition. The other options are not valid hard disk partitions, because they do not follow the Linux convention. For example:

• /dev/ttyS0 is a serial port device, not a hard disk device4.
• /dev/sata0 is not a valid device name, because it does not specify the partition number. It should be something like /dev/sata0p1 or /dev/sata0p2, etc.
• /dev/part0 is not a valid device name, because it does not specify the device type or the partition number. It should be something like /dev/sdXp0 or /dev/hdXp0, etc.
• /dev/sda/p2 is not a valid device name, because it uses a slash (/) instead of a number to indicate the partition. It should be something like /dev/sda2 or /dev/sda3, etc.

References: 1: Hard drive/device partition naming convention in Linux - Unix & Linux Stack Exchange 2: Hard drive partition naming convention in Linux - Ask Ubuntu 3: C.4. Device Names in Linux - Debian 4: What is /dev/ttyS0? - Quora

Explanation

The chmod command is used to change the permissions of files and directories. The permissions are represented by three sets of three characters, indicating the permissions for the owner, the group, and the others. Each character can be either r (read), w (write), x (execute), or - (no permission). The chmod command can use either symbolic or numeric mode to specify the permissions. In this question, the numeric mode is used, which consists of three digits from 0 to 7. Each digit is the sum of the permissions for each set, where r is 4, w is 2, and x is 1. For example, 7 means rwx, 6 means rw-, and 4 means r–. Therefore, the command chmod 654 file.txt sets the permissions as follows:

• The first digit 6 means rw- for the owner, which means the owner can read and write the file, but not execute it.
• The second digit 5 means r-x for the group, which means the group can read and execute the file, but not write it.
• The third digit 4 means r-- for the others, which means the others can only read the file, but not write or execute it.

The resulting permissions are -rw-r-xr–, which is the correct answer. The other options are incorrect because they either have the wrong permissions or the wrong file type. A regular file does not have the d (directory) prefix, and a directory cannot have the - (no file type) prefix. References:

• Linux Essentials Version 1.6 Objectives: 4.1. Ownership and Permissions1
• Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Chapter 8. Security and File Permissions - 8.1. Ownership and Permissions - 8.1.1. The chmod Command2
• Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Appendix A. Answers to the Exercises - Chapter 8. Security and File Permissions - 8.1. Ownership and Permissions - Exercise 8.1.12

The shell prompt is a symbol or a string of characters that indicates the shell is ready to accept commands. The shell prompt can be customized by the user or by the system administrator. The default shell prompt for a normal user is usually a dollar sign ($), while the default shell prompt for the root user is usually a hash sign (#). The root user is the superuser or the administrator of the system, who has full access and control over all files, commands, and resources. Running commands as root can be dangerous, as it can cause irreversible damage to the system if done incorrectly. Therefore, it is advisable to use sudo or su to run commands as root only when necessary, and to switch back to a normal user as soon as possible. The shell prompt indicates the shell is running with root privileges when it ends with a hash sign (#). References:

• Linux Essentials - Linux Professional Institute (LPI)
• Running a shell command as root - Unix & Linux Stack Exchange

 Reverse DNS lookups query DNS servers for a PTR (pointer) record; if the server does not have a PTR record, it cannot resolve a reverse lookup. PTR records store IP addresses with their segments reversed, and they append “.in-addr.arpa” to that. For example, if a domain has an IP address of 192.0.2.1, the PTR record will store the domain’s information under 1.2.0.192.in-addr.arpa. In IPv6, the latest version of the Internet Protocol, PTR records are stored within the “.ip6.arpa” domain instead of ".in-addr.arpa."1 Therefore, the name of the IP address 198.51.100.165 is stored in the PTR record for 165.100.51.198.in-addr.arpa. References: 1: Reverse DNS lookup - Wikipedia 1

 The PATH environment variable is a special variable that contains a list of directories that the system searches when looking for a command to execute12. The purpose of the PATH variable is to make it easier and faster for users to run commands without having to type the full path to the executable file. For example, if you want to run the ls command, which is located in the /bin directory, you don’t have to type /bin/ls every time. You can just type ls, and the system will find the executable file in the /bin directory, which is one of the directories in the PATH variable. The PATH variable can be viewed with the echo command12:

$ echo $PATH

The PATH variable can also be modified by adding or removing directories, either temporarily or permanently, depending on the user’s needs12. For example, if you have acustom script or program in your home directory, and you want to run it from anywhere, you can add your home directory to the PATH variable with the export command12:

$ export PATH=$PATH:~/myprogram

This will append your home directory to the end of the PATH variable, and the system will search it last when looking for a command. To make this change permanent, you need to edit a configuration file, such as ~/.bashrc or ~/.profile, and add the export command there12.

References:

• How To View and Update the Linux PATH Environment Variable | DigitalOcean
• Linux path environment variable - Linux command line - LinuxConfig.org

The tar command is used to create or extract compressed archive files that contain multiple files or directories. The tar command has the following syntax: tar [options] [archive-file] [file or directory…]. The options argument specifies how the tar command should operate and what kind of compression should be used. The archive-file argument is the name of the archive file to be created or extracted. The file or directory argument is the name of one or more files or directories to be included in or extracted from the archive file.

The following are some of the common options for the tar command:

• -c: create a new archive file.
• -x: extract files from an existing archive file.
• -t: list the contents of an archive file.
• -v: show the progress of the operation.
• -f: specify the name of the archive file.
• -z: use gzip compression or decompression.
• -j: use bzip2 compression or decompression.
• -J: use xz compression or decompression.

The options -z and -j are used to handle compression with the tar command. The option -z uses the gzip program to compress or decompress the archive file, which usually has the extension .tar.gz or .tgz. The option -j uses the bzip2 program to compress or decompress the archive file, which usually has the extension .tar.bz2 or .tbz. Both gzip and bzip2 are popular compression programs that reduce the size of files by removing redundant or unnecessary information.

For example, to create a compressed archive file called backup.tar.gz that contains the files and directories in the current directory, the following command can be used:

tar -czvf backup.tar.gz .

To extract the files and directories from the archive file backup.tar.gz to the current directory, the following command can be used:

tar -xzvf backup.tar.gz

To create a compressed archive file called backup.tar.bz2 that contains the files and directories in the current directory, the following command can be used:

tar -cjvf backup.tar.bz2 .

To extract the files and directories from the archive file backup.tar.bz2 to the current directory, the following command can be used:

tar -xjvf backup.tar.bz2

The other options in the question are not related to compression. The option -bz is invalid, as there is no such option for the tar command. The option -g is used to create or update an incremental archive file, which only contains the files that have changed since the last backup. The option -z2 is also invalid, as there is no such option for the tar command. References:

• Linux Essentials Version 1.6 Objectives: 3.1. Archiving Files on the Command Line1
• Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Chapter 9. The Power of the Command Line - 9.1. Archiving Files on the Command Line - 9.1.1. The tar Command2
• Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Appendix A. Answers to the Exercises - Chapter 9. The Power of the Command Line - 9.1. Archiving Files on the Command Line - Exercise 9.1.12

The passwd command in Linux is used to change the password of a user account. A normal user can run passwd to change their own password, and a system administrator (the superuser) can use passwd to change another user’s password, or define how that account’s password can beused or changed1. The passwd command can also be used to lock or unlock a user account. Locking a user account means disabling the user’s ability to log in to the system, while unlocking a user account means restoring the user’s ability to log in. To lock a user account, the passwd command can be used with the -l option, followed by the username. To unlock a user account, the passwd command can be used with the -u option, followed by the username12. The passwd command cannot be used to change a user’s username, create a new user account, or create a new user group. These tasks require different commands, such as usermod, useradd, orgroupadd345. References: 1: Linux Passwd Command Help and Examples 2: Passwd command in Linux: 8 Practical Examples 3: usermod(8) - Linux man page 4: useradd(8) - Linux man page 5: groupadd(8) - Linux man page

A process ID on Linux is a unique integer value that identifies a running process. The process ID can range from 0 to a maximum limit, which is usually 32768 or higher, depending on the system configuration. The process ID of 0 is reserved for the kernel’s idle task, and the process ID of 1 is reserved for the init system, which is the first process launched by the kernel. The process IDs are assigned sequentially to new processes, and are recycled when a process terminates. Therefore, the only valid value for a process ID among the given options is 21398, which is an integer within the possible range. The other values are not valid process IDs because they are either strings, hexadecimal numbers, or file paths, which do not match the format of a process ID on Linux. References:

• Linux Essentials - Linux Professional Institute (LPI)
• How Are Linux PIDs Generated? | Baeldung on Linux

 The dmesg command is used to display the messages from the kernel that are stored in a ring buffer. A ring buffer is a fixed-size data structure that overwrites the oldest entries when it is full. Therefore, the dmesg command might not display older information because it was overwritten by newer information. The dmesg command is useful for troubleshooting system issues and checking hardware information. The dmesg command is not used to trace the execution of a command, send messages to user sessions, or output the system journal. Those functions are performed by other commands such as strace, write, and journalctl respectively. References: : [dmesg] : [Ring buffer] : [strace] : [write (Unix)] : [journalctl]4)