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

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 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

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 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

 Ubuntu Linux LTS and Red Hat Enterprise Linux are two Linux distributions that meet the requirements of hosting services for a period of several years and receiving important security updates from their Linux distribution. LTS stands for Long Term Support, which means that these versions of Ubuntu Linux are supported by Canonical, the company behind Ubuntu, for five years with security patches, bug fixes, and software updates1. Red Hat Enterprise Linux is a commercial Linux distribution that offers a stable and secure platform for enterprise applications, with a 10-year life cycle and regular security updates from Red Hat, the company behind RHEL2. Fedora Linux, Debian GNU/Linux Unstable, and Ubuntu Linux non-LTS are not suitable for the requirements, because they have shorter support cycles and are more focused on providing the latest features and software versions, rather than stability and security. Fedora Linux releases a new version every six months and each version is supported for 13 months3. Debian GNU/Linux Unstable is the development branch of Debian, which is constantly updated with new packages and changes, but is not intended for production use4. Ubuntu Linux non-LTS releases a new version every six months and each version is supported for nine months1. References:

• Ubuntu release cycle | Ubuntu
• Red Hat Enterprise Linux Life Cycle - Red Hat Customer Portal
• Fedora Release Life Cycle - Fedora Project Wiki
• Debian Unstable - Debian Wiki

 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 correct commands to output the content of the file Texts 2.txt are A and E. These commands use the cat command, which stands for concatenate, to display the content of one or more files. The cat command can take one or more filenames as arguments and print their content to the standard output (usually the terminal screen)12. The commands A and E use different ways to deal with the space character in the filename. The space character is a special character in Linux that separates words and commands. To prevent the shell from interpreting the space as a word separator, the commands A and E use either of the following methods34:

• Option A uses single quotes (') around the filename to preserve the literal value of the space character. This tells the shell to treat the filename as a single argument and pass it to the cat command. For example: cat ‘Texts 2.txt’
• Option E uses a backslash () before the space character to escape its special meaning. This tells the shell to ignore the space as a word separator and treat it as part of the filename. For example: cat Texts\ 2.txt

The other options are incorrect because they use different syntax that do not output the content of the file. For example:

• Option B uses a double dash (–) before the filename to indicate the end of options. This is usually used to prevent the shell from interpreting a filename that starts with a dash (-) as an option. However, in this case, the filename does not start with a dash, so the double dash is unnecessary and will cause the command to fail. For example: cat – Texts 2.txt
• Option C uses vertical bars (|) around the filename to indicate a pipe. A pipe is a way of connecting the output of one command to the input of another command. However, in this case, there is no command before or after the pipe, so the pipe is meaningless and will cause the command to fail. For example: cat |Texts 2.txt|
• Option D uses single quotes (') and a backslash () together around the filename. This is redundant and will cause the command to fail. The single quotes already preserve the literal value of the space character, so the backslash is not needed. Moreover, the backslash inside the single quotes will be treated as part of the filename, not as an escape character. For example: cat ‘Texts\ 2.txt’

References: 1: How to Use Linux Cat Command (With Examples) - phoenixNAP 2: Cat command in Linux with examples - GeeksforGeeks 3: How to escape spaces in path during scp copy in Linux? - Stack Overflow 4: How to handle spaces in file names when using xargs on find results? - Ask Ubuntu

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 /proc/ directory is a virtual file system that contains information about the system and the processes running on it. It is not a conventional file system that stores files on a disk, but rather a dynamic view of the kernel’s data structures. One of the features of the /proc/ directory is that it contains one subdirectory for each process running on the system, which is named after the process ID (PID). For example, the subdirectory /proc/1/ contains information about the process with PID 1, which is usually the init process. The process subdirectories contain various files that provide information about the process, such as its status, memory usage, open files, environment variables, command line arguments, and more. The /proc/ directory also contains a symbolic link called ‘self’, whichpoints to the process that is accessing the /proc/ file system. Therefore, the correct answer is D. One directory per running process.

The other options are incorrect because:

• A. One directory per installed program. This is not true, as the /proc/ directory does not contain information about installed programs, but only about running processes. Installed programs are usually stored in other directories, such as /bin/, /usr/bin/, /opt/, etc.
• B. One device file per hardware device. This is not true, as the /proc/ directory does not contain device files, but only virtual files that represent kernel data. Device files are usually stored in the /dev/ directory, which is another special file system that provides access to hardware devices.
• C. One file per existing user account. This is not true, as the /proc/ directory does not contain information about user accounts, but only about processes. User accounts are usually stored in the /etc/ directory, which contains configuration files, such as /etc/passwd/ and /etc/shadow/, that define the users and their passwords.
• E. One log file per running service. This is not true, as the /proc/ directory does not contain log files, but only information files. Log files are usually stored in the /var/log/ directory, which contains various files that record the activities of the system and the services.

References:

• The /proc Filesystem — The Linux Kernel documentation
• A Beginner’s Guide to the /proc File System in Linux - Tecmint
• Appendix E. The proc File System Red Hat Enterprise Linux 6 | Red Hat …
• Chapter 5. The proc File System Red Hat Enterprise Linux 4 | Red Hat …
• proc file system in Linux - GeeksforGeeks

 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 correct command to create an archive file work.tar from the contents of the directory ./work/ is tar –cf work.tar ./work/. This command uses the -c option to create a new archive, the -f option to specify the file name, and the ./work/ argument to indicate the source directory. The other commands are incorrect for various reasons:

• A. tar --new work.tar ./work/ is incorrect because there is no --new option in the tar command. The correct option for creating a new archive is --create or -c.
• C. tar –create work.tgz –content ./work/ is incorrect because the -content option is not valid. The correct option for specifying the source files or directories is --files-from or -T. Also, the work.tgz file name implies compression, but the command does not use any compression option such as -z, -j, or -J.
• D. tar work.tar < ./work/ is incorrect because the tar command does not accept input redirection from the standard input. The correct way to use the tar command is to provide the options and arguments after the command name.
• E. tar work > work.tar is incorrect because the tar command does not produce output redirection to the standard output. The correct way to use the tar command is to use the -f option to specify the output file name. References: : tar command in Linux with examples - GeeksforGeeks : tar Command in Linux With Examples | phoenixNAP KB

The main difference between hard disk drives (HDDs) and solid state drives (SSDs) is the way they store and access data. HDDs use a spinning disk (platter) and a moving head to read and write data, while SSDs use flash memory chips that have no moving parts. This makes SSDs faster, quieter, and more durable than HDDs, but also more expensive and less spacious. HDDs and SSDs are both I/O devices that can be used to boot the system and store data, but they have different advantages and disadvantages depending on the use case. References:

• Difference between Hard Disk Drive (HDD) and Solid State Drive (SSD)
• Hard Disk Drive (HDD) vs. Solid State Drive (SSD): What’s the Difference?
• How to Check Whether Your Disk Is an SSD or HDD on Linux

 The top command is a Linux command that shows the running processes on the system. It provides a dynamic real-time view of the system performance and resource usage. The top command can display various information about the processes, such as their process ID, user, priority, state, CPU and memory usage, command name, and more. The top command can also sort the processes by different criteria, such as CPU or RAM consumption, by using the interactive commands. The top command is useful for monitoring the system load and identifying the processes that are consuming the most resources. References:

• Linux Essentials Topic 104: The Linux Operating System, section 104.3: Basic features and commands of the Linux standard shells.
• Linux Essentials Topic 106: Security and File Permissions, section 106.4: Monitor and manage Linux processes.

 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

 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 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 correct command to search for the file foo.txt under the directory /home is find /home –name foo.txt. This command uses the find command, which is used to search for files and directories that match certain criteria. The first argument, /home, specifies the starting point of the search. The second argument, -name, indicates that the search is based on the name of the file or directory. The third argument, foo.txt, is the name of the file to be searched for. The find command will recursively search all the subdirectories under /home and print the path of any file or directory that matches the name foo.txt.

The other commands are incorrect for various reasons:

• A. search /home –file foo.txt is incorrect because there is no such command as search in Linux. The correct command for searching files and directories is find.
• B. search /home foo.txt is incorrect because, as mentioned above, there is no search command in Linux. Also, this command does not use any option to specify the search criteria, such as -name, -type, -size, etc.
• C. find /home – file foo.txt is incorrect because the option -file is not valid. The correct option for specifying the type of file or directory is -type, followed by a letter that indicates the type, such as f for regular file, d for directory, l for symbolic link, etc. For example, find /home -type f -name foo.txt would search for a regular file named foo.txt under /home.
• E. find /home foo.txt is incorrect because this command does not use any option to specify the search criteria, such as -name, -type, -size, etc. This command will search for any file or directory that has foo.txt as part of its name, not exactly as its name. For example, this command will also match a file named barfoo.txt or a directory named foo.txt.bak.

References: : find command in Linux with examples - GeeksforGeeks : 15 Super Useful Examples of Find Command in Linux

The files /etc/passwd and /etc/group are the source of the information in the following output:

uid=1000 (bob) gid=1000 (bob) groups=1000 (bob), 10 (wheel), 150 (docker), 1001 (libvirt) (wireshark), 989

The /etc/passwd file contains information about user accounts, such as the username, password, user ID (UID), group ID (GID), full name, home directory, and login shell1. The /etc/group file contains information about groups, such as the group name, password, group ID (GID), and members2.

The output shows the UID, GID, and group membership of the user bob. The UID and GID of bob are 1000, which can be found in the /etc/passwd file. The groups that bob belongs to are bob, wheel, docker, libvirt, wireshark, and 989, which can be found in the /etc/group file. The group names are shown in parentheses after the GID, except for the last group, which has no name.

The other options are not files that store user and group information in Linux. The /etc/id file does not exist by default. The /home/index file is not a standard file and has no relation to user and group information. The /var/db/users file is not a standard file and has no relation to user and group information. References:

• Linux Essentials Exam Objectives, Version 1.6, Topic 103.1, Weight 2
• Linux Essentials Certification Guide, Chapter 3, Page 51-52
• Linux Filesystem Hierarchy, Chapter 3, Page 17-18
• Linux Users and Groups, Chapter 2, Page 9-10

The grep command is used to search for a pattern in a file or input. The -i option makes the search case-insensitive, meaning that it will match both uppercase and lowercase letters. The grep command takes the pattern as the first argument and the file name as the second argument. Therefore, the command grep -i linux operating-systems.txt will find all lines in the file operating-systems.txt which contain the term linux, regardless of the case. References: Linux Essentials - Topic 103: Finding Linux Documentation and Linux Essentials - Topic 104: Command Line Basics

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

 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