010-160 Linux Essentials Certificate Exam - version 1.6 Questions and Answers

 A shell script is a file that contains a series of commands that can be executed by a shell interpreter. To execute a shell script, there are two main methods:

• Method 1: Specify the path to the script file. This method requires that the script file has the execute permission, which can be granted by using the chmod command. The script file also needs to have a shebang line at the beginning, which indicates which interpreter to use for the script. For example, #!/bin/bash means to use the bash interpreter. To execute the script using this method, you can type the absolute path or the relative path to the script file. If you are in the same directory as the script file, you can use the ./ prefix to indicate the current directory. For example, ./test.sh will execute the test.sh script in the current directory.
• Method 2: Pass the script file as an argument to the interpreter. This method does not require the execute permission or the shebang line for the script file. You can simply use the name of the interpreter followed by the script file name as an argument. For example, bash test.sh will execute the test.sh script using the bash interpreter.

Therefore, the correct answers are D and E. A. run test.sh is incorrect because run is not a valid command in Linux. B. ${test.sh} is incorrect because this syntax is used for variable expansion, not for executing a script. C. cmd ./test.sh is incorrect because cmd is not a valid command in Linux. References:

• Linux Essentials Topic 105: The Power of the Command Line, section 105.3: Basic shell scripting.
• How to Run a Shell Script in Linux [Essentials Explained] - It’s FOSS
• How To Execute a Command with a Shell Script in Linux | DigitalOcean
• How To Run the .sh File Shell Script In Linux / UNIX

 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

 Linux hardware drivers are software components that enable the Linux kernel to communicate with various devices, such as keyboards, mice, printers, scanners, network cards, etc. Drivers are either compiled into the Linux kernel or are loaded as kernel modules. Kernel modules are pieces of code that can be loaded and unloaded into the kernelon demand. They extend the functionality of the kernel without requiring to rebuild or reboot the system. Drivers that are compiled into the kernel are always available, but they increase the size and complexity of the kernel. Drivers that are loaded as kernel modules are only available when needed, but they require a matching version of the kernel and the module. Linux supports a large number of hardware devices, thanks to the efforts of the open source community and some vendors who provide drivers for their products. However, some devices may not have a driver available for Linux, or may require a proprietary driver that is not included in the Linux distribution. In such cases, the user may need to install the driver manually from the vendor’s website or from a third-party repository. References:

• Linux Essentials - Linux Professional Institute (LPI), section 2.2.1
• LPI Linux Essentials Study Guide: Exam 010 v1.6, 3rd Edition, chapter 3, page 67.

 In Linux, every file and directory is associated with an owner and a group. The owner is the user who created the file or directory, and the group is the group to which the owner belongs. Therefore, each file is owned by exactly one user and one group. This is true for option A. The other options are false for the following reasons:

• Option B: The owner of a file does not always have full permissions when accessing the file. The permissions are determined by the file mode, which can be changed by the owner or the root user. The file mode specifies the read, write, and execute permissions for the owner, the group, and others. The owner can have different permissions than the group or others.
• Option C: The user owning a file does not have to be a member of the file’s group. The owner can change the group ownership of the file to any group on the system, regardless of whether the owner belongs to that group or not. However, only the root user or a user with the CAP_CHOWN capability can change the group ownership to a group that the owner is not a member of.
• Option D: When a user is deleted, all files owned by the user do not disappear. The files remain on the system, but their owner is changed to an invalid user ID (UID). The files can still be accessed by the group or others, depending on the permissions. The files can also be reclaimed by the root user or a user with the CAP_CHOWN capability, who can change the owner to a valid user.
• Option E: The owner of a file can be changed once it is assigned to an owner. The owner can transfer the ownership to another user, or the root user or a user with the CAP_CHOWN capability can change the owner to any user on the system. The command to change the owner of a file is chown. References: 1: Chown Command in Linux (File Ownership) | Linuxize 2 3: Linux File Permissions and Ownership Explained with Examples 4 2: 3 Ways to Find File Owner in Linux - howtouselinux 1

The general structure of a for loop in a shell script is as follows12:

for variable in list do commands done

The variable is the name of a loop counter or iterator that takes on the values of the items in the list. The list can be a sequence of words, numbers, filenames, or the output of a command. The commands are the body of the loop that are executed for each value of the variable. The do and done keywords mark the beginning and the end of the loop body.

The option C. for file in *.txt do echo $i done follows this structure, with the variable being file, the list being *.txt (which matches all the files with the .txt extension in the current directory), and the command being echo $i (which prints the value of the variable i, which is presumably set somewhere else in the script).

The other options are incorrect because:

• A. for *.txt as file => echo $file uses an invalid syntax for a for loop. The as keyword is not part of the shell script syntax, and the => symbol is not a valid operator. The correct way to write this loop would be:

for file in *.txt do echo $file done

• B. for *.txt ( echo $i ) uses an invalid syntax for a for loop. The parentheses are not part of the shell script syntax, and the loop body is missing the do and done keywords. The correct way to write this loop would be:

for i in *.txt do echo $i done

• D. for ls *.txt exec {} ; uses an invalid syntax for a for loop. The ls command is not a valid variable name, and the exec {} ; is not a valid command. This looks like a mix of a for loop and a find command. The correct way to write this loop would be:

for file in *.txt do exec $file done

• E. foreach @{file} { echo $i } uses an invalid syntax for a for loop. The foreach keyword is not part of the shell script syntax, and the @{file} and { echo $i } are not valid expressions. This looks like a mix of a for loop and a Perl syntax. The correct way to write this loop would be:

for file in * do echo $file done

References:

• Looping Statements | Shell Script - GeeksforGeeks
• How do I write a ‘for’ loop in Bash? - Stack Overflow

 The correct command to copy the contents of the directory /etc/, including all sub-directories, to /root/ is cp -r /etc/* /root. This command uses the cp command, which stands for copy, and is used to copy files and directories on Linux and Unix systems. The command also uses the following options and arguments123:

• The -r option, which stands for recursive, and tells cp to copy all files and sub-directories of the source directory. Alternatively, the -R option can be used, which has the same effect as -r.
• The /etc/* argument, which specifies the source directory and all its contents. The asterisk (*) is a wildcard character that matches any file or directory name. This argument tells cp to copy everything inside the /etc/ directory, but not the directory itself.
• The /root argument, which specifies the destination directory. This argument tells cp to copy the source files and sub-directories to the /root/ directory.

The other options are incorrect because they use different commands or syntax that do not copy the contents of the directory /etc/, including all sub-directories, to /root/. For example:

• Option A uses the copy command, which is not a valid Linux command. The correct command is cp.
• Option C uses the -v option, which stands for verbose, and tells cp to print verbose output. This option does not affect the copying process, but only the output. It also does not include the -r or -R option, which is necessary to copy the sub-directories.
• Option D uses the rcp command, which stands for remote copy, and is used to copy files between different hosts on a network. This command is not relevant for copying files on the same host.
• Option E uses the -R option, which is correct, but also uses the . argument, which is incorrect. The dot (.) is a special character that matches any single character. This argument tells cp to copy only the files and directories that have a dot in their name, which may exclude some files and directories that do not have a dot.

References: 1: Cp Command in Linux (Copy Files) | Linuxize 2: cp command in Linux with examples - GeeksforGeeks 3: How to Copy Files and Directories in the Linux Terminal

To remove a directory, you need to use a command that can delete directories, not just files. The rm command can only remove files by default, unless you use the -r option, which stands for recursive. This option tells rm to delete the directory and all of its contents, including subdirectories and files. The rmdir command can also remove directories, but only if they are empty. If the directory contains any files or subdirectories, rmdir will fail and display an error message. Therefore, the correct commands to remove Downloads, assuming it is empty, are rmdir Downloads and rm -r Downloads. The other commands are either invalid or do not work on directories. References:

• Linux Essentials - Linux Professional Institute (LPI), section 2.3.1
• LPI Linux Essentials Study Guide: Exam 010 v1.6, 3rd Edition, chapter 4, page 93.

The distribution’s package repository is the preferred source for the installation of new applications in a Linux based operating system. A package repository is a collection of software packages that are maintained by the distribution and can be easily installed, updated, or removed using a package manager. Package repositories offer several advantages, such as:

• They ensure compatibility and stability with the system and other packages.
• They provide security updates and bug fixes for the packages.
• They reduce the risk of malware or corrupted files.
• They simplify the dependency management and configuration of the packages.

The other sources are not preferred because they may not offer these benefits and may cause problems with the system. The vendor’s version management system, the vendor’s website, or a CD-ROM disk may contain packages that are not compatible with the distribution or may conflict with other packages. A retail store may not have the latest or the most suitable packages for the system. References:

• Linux Essentials - Linux Professional Institute (LPI), section 1.3 Installing, Updating and Removing Software Packages
• LPI Linux Essentials Study Guide: Exam 010 v1.6, 3rd Edition, chapter 4 Working on the Command Line, section 4.2 Managing Software
• Table of Contents - Linux Professional Institute Certification Programs, section 1.3 Installing, Updating and Removing Software Packages

The sort command is used to sort the lines of a file or a stream of input according to a specified criterion, such as alphabetical order, numerical order, reverse order, etc. By default, the sort command sorts the lines in ascending alphabetical order, using the firstcharacter of each line as the key. For example, the command sort data.csv will sort the lines of the file data.csv in alphabetical order and display the output on the screen. If you want to save the sorted output to a new file, you can use the redirection operator (>) to specify the output file name. For example, the command sort data.csv > sorted_data.csv will sort the lines of the file data.csv in alphabetical order and save the output to a new file named sorted_data.csv. The other commands are either invalid or do not perform the sorting operation. The a…z command does not exist, the abc command is a text editor, the wc command counts the number of words, lines, and bytes in a file, and the grep command searches for a pattern in a file or a stream of input. Therefore, the correct answer is B. References:

• Linux Essentials - Linux Professional Institute (LPI), section 2.3.2
• LPI Linux Essentials Study Guide: Exam 010 v1.6, 3rd Edition, chapter 4, page 95.

The zip command is used to create compressed archive files that can contain one or more files or directories. The zip command takes the name of the archive file as the first argument, followed by the names of the files or directories to be included in the archive. You can also use wildcards to match multiple files or directories with a common pattern. For example, the command zip poems.zip *.txt will create the ZIP archive poems.zip containing all files in the current directory whose names end in .txt. The other commands are either invalid or do not perform the desired operation. The command zip *.txt > poems.zip will try to create an archive for each file ending in .txt and redirect the output to poems.zip, which is not a valid archive file. The command zcat *.txt poems.zip will try to decompress and concatenate the contents of the files ending in .txt and poems.zip, which is not a valid ZIP file. The command zip cfz poems.zip *.txt will fail because the options c, f, and z are not valid for the zip command. The command cat *.txt | zip poems.zip will try to read the contents of the files ending in .txt from the standard input and create an archive named poems.zip, but this will not preserve the file names or attributes of the original files. References:

• Linux Essentials - Linux Professional Institute (LPI), section 3.1.1
• 3.1 Archiving Files on the Command Line - Linux Professional Institute Certification Programs, slide

 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 correct command to set the variable USERNAME to the value bob is USERNAME=bob. This command assigns the string bob to the variable name USERNAME, using the equal sign (=) as the assignment operator. There is no space around the equal sign, and the variable name and value are case-sensitive. This command sets a shell variable, which is only valid in the current shell session. To make the variable an environment variable, which can be inherited by child processes and subshells, you need to use the export command, such as export USERNAME=bob. The other commands are not valid for setting variables in Linux. The set command is used to set orunset shell options and positional parameters, not variables. The $ sign is used to reference the value of a variable, not to assign it. The == sign is used for comparison, not assignment. The var keyword is not used in Linux, but in some other programming languages. The <= sign is used for redirection, not assignment. References:

• Linux Essentials - Linux Professional Institute (LPI)
• How to Set and List Environment Variables in Linux | Linuxize

The su command stands for substitute user or switch user. It allows you to run a shell or a command as another user, usually the superuser or root. To use the su command, you need to know the password of the target user. For example, if you want to switch to the root user, you can type su - and enter the root password. This will give you a root shell, where you can execute commands with administrative privileges. To exit the root shell, you can type exit or press Ctrl-D. The su command is not the default shell of the root account, nor can it only be used by the root user. It can be used by any user who knows the password of another user. The su command does not change the name of the main administrator account, which is always root on Linux systems. The su command also does not lock the root account in specific time frames, although there are other ways to do that, such as using the pam_time module. References:

• Linux Essentials - Linux Professional Institute (LPI), section 5.1.1
• LPI Linux Essentials Study Guide: Exam 010 v1.6, 3rd Edition, chapter 9, page 219.

 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 host command is used to resolve a DNS name to an IP address or vice versa. It can also perform other DNS queries, such as finding the mail servers for a domain. The host command has the following syntax: host [options] [name] [server]. The name argument can be a hostname, such as www.lpi.org, or an IP address, such as 192.168.0.1. The server argument is optional and specifies the name or IP address of the DNS server to query. If no server is given, the default system resolver is used.  References:

• Linux Essentials Version 1.6 Objectives: 1.4.1. Demonstrate an understanding of the purpose and types of DNS records1
• Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Chapter 10. Network Fundamentals - 10.3. DNS and Hostname Resolution - 10.3.1. The host Command2
• Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Appendix A. Answers to the Exercises - Chapter 10. Network Fundamentals - 10.3. DNS and Hostname Resolution - Exercise 10.3.12

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

 The sort command is used to sort the lines of a text file or the output of another command in alphabetical, numerical, or other order. The sort command has the following syntax: sort [options] [file…]. The file argument is the name of one or more files to be sorted. If no file is given, the sort command reads from the standard input, which is usually the keyboard or the output of another command.

The | (pipe) symbol is used to connect the output of one command to the input of another command. This allows the creation of pipelines of commands that process data sequentially. The pipe symbol has the following syntax: command1 | command2. The command1 argument is the name of the first command, whose output is sent to the input of the second command. The command2 argument is the name of the second command, which receives the output of the first command as its input.

Therefore, the command export-logs | sort sorts the output of the export-logs command in alphabetical order. The export-logs command is assumed to be a custom command that exports some logs to the standard output. The sort command receives the output of the export-logs command as its input and sorts it according to the default criteria, which is the first character of each line. The sorted output is then displayed on the screen or can be redirected to a file or another command.

The other options in the question are incorrect because they use the wrong symbols to connect the commands. The < (input redirection) symbol is used to read the input of a command from a file instead of the keyboard. The > (output redirection) symbol is used to write the output of a command to a file instead of the screen. The & (background) symbol is used to run a command in the background, which means the command does not wait for user input and allows the user to run other commands simultaneously. The <> (bidirectional redirection) symbol is used to read and write the input and output of a command from and to the same file. None of these symbols can be used to sort the output of the export-logs command. References:

• Linux Essentials Version 1.6 Objectives: 3.2. Searching and Extracting Data from Files1
• Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Chapter 9. The Power of the Command Line - 9.2. Searching and Extracting Data from Files - 9.2.1. The sort Command2
• Linux Essentials Version 1.6 Exam Study Resources: Linux Essentials Manual - Chapter 9. The Power of the Command Line - 9.3. Turning Commands into a Script - 9.3.1. Pipes and Redirection2
• 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 - 9.2. Searching and Extracting Data from Files - Exercise 9.2.12
• 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 - 9.3. Turning Commands into a Script - Exercise 9.3.12

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

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.

The return value of a shell script after successful execution is 0. This is a convention followed by most UNIX and Linux commands, programs, and utilities. A return value of 0 indicates that the command or script completed successfully, without any errors. A return value of non-zero (1-255) indicates that the command or script failed, and the value can be interpreted as an error code. The return value of a command or script is stored in the special variable $? and can be used to test the outcome of a command or script123. For example, the following script will print a message based on the return value of the ls command:

#!/bin/bash ls if [ $? -eq 0 ]; then echo “ls command executed successfully” else echo “ls command failed” fi

References: 1: Exit and Exit Status - Linux Documentation Project 2: Linux Passwd Command Help and Examples 3: bash - Which is the best way to check return result? - Unix & Linux Stack Exchange

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