010-160 Questions and Answers

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

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 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

RPM stands for RPM Package Manager (formerly known as Red Hat Package Manager), which is a powerful, command-line package management tool developed for the Red Hat operating system. It is now used as a core component in many Linux distributions such as CentOS, Fedora, Oracle Linux, openSUSE and Mageia1. RPM can install, uninstall,and query individual software packages, but it cannot manage dependency resolution like YUM2. YUM is another package management tool that is based on RPM and can handle dependencies automatically. YUM is the primary package management tool for installing, updating, removing, and managing software packages in Red Hat Enterprise Linux2. Therefore, the correct answer is B. rpm, as it is the underlying package management tool used in Red Hat-based Linux systems. References:

• Linux package management with YUM and RPM | Enable Sysadmin
• Chapter 13. Package Management Tool Red Hat Enterprise Linux 5 | Red Hat Customer Portal
• Difference Between YUM and RPM | 2DayGeek

 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

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

 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 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 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 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

DHCP stands for Dynamic Host Configuration Protocol. It is a protocol that provides quick, automatic, and central management for the distribution of IP addresses within a network. It also configures other network information, such as the subnet mask, default gateway, and DNS server information, on the device1. DHCP uses a client/server architecture, where a DHCP server issues unique IP addresses and automatically configures the devices that request them2. DHCP allows devices to move freely from one network to another and receive an IP address automatically, which is helpful with mobile devices1.

The other options are not protocols used for automatic IP address configuration. NFS stands for Network File System, which is a protocol that allows a user to access and modify files over a network as if they were on their own computer. LDAP stands for Lightweight Directory Access Protocol, which is a protocol that provides access to a centralized directory service that stores information about users, groups, computers, and other resources on a network. SMTP stands for Simple Mail Transfer Protocol, which is a protocol that enables the sending and receiving of email messages over a network. DNS stands for Domain Name System, which is a protocol that translates domain names into IP addresses and vice versa. References:

• Linux Essentials Exam Objectives, Version 1.6, Topic 105.1, Weight 4
• What Is DHCP? (Dynamic Host Configuration Protocol) - Lifewire
• Dynamic Host Configuration Protocol (DHCP) | Microsoft Learn
• Dynamic Host Configuration Protocol - Wikipedia
• How does AutoIP work? - Barix
• [Network File System - Wikipedia]
• [Lightweight Directory Access Protocol - Wikipedia]
• [Simple Mail Transfer Protocol - Wikipedia]
• [Domain Name System - Wikipedia]

The useradd command in Linux is used to create new user accounts on the system1. The -m option tells the command to create the user’s home directory as /home/username and copy the files from /etc/skel directory to the user’s home directory2. The /etc/skel directory contains the default configuration files for new users3. Therefore, the command useradd -m tux will add the new user tux and create the user’s home directory with default configuration files. The other options are either invalid or do not create the user’s home directory. 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
• Linux useradd Command Tutorial for Beginners (15 Examples)

The correct statement about Free Software is that it may be modified by anyone using it. This is one of the four essential freedoms of Free Software, which are: the freedom to run the program as you wish, for any purpose; the freedom to study how the program works, and change it so it does your computing as you wish; the freedom to redistribute copies so you can help your neighbor; and the freedom to distribute copies of your modified versions to others1. Access to the source code is a precondition for these freedoms1.

The other statements are false for the following reasons:

• Free Software is not developed by volunteers only. It can be developed by anyone, including individuals, companies, organizations, or communities. Some Free Software developers are paid for their work, while others do it as a hobby or for social benefit1.
• Free Software does not have to be available free of charge. It can be sold or given away for any price. The term “free” refers to the users’ freedom, not the price of the software1. However, Free Software users have the freedom to redistribute copies, so they can obtain the software at no charge from someone who has a copy1.
• Free Software does not only run on Linux. It can run on any operating system that supports it, such as Windows, MacOS, BSD, or Android. Linux is an example of a Free Software operating system, but not the only one1.
• Free Software is not only distributed as a compiled binary. It can also be distributed as source code, or both. In fact, Free Software must provide access to the source code, otherwise the users cannot study or modify the software1.

References:

• What is Free Software? - GNU Project - Free Software Foundation

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

The UID of the user root is always 0 on Linux systems. This is because the kernel uses the UID 0 to check for the superuser privileges and grant access to all system resources. The name of the user account with UID 0 is usually root, but it can be changed or have aliases. However, some applications may expect the name root and not work properly with a different name. The UID 0 is reserved for the root user and cannot be assigned to any other user. The UID 0 is stored in the /etc/passwd file along with other user information. References:

• Linux Essentials Topic 104: The Linux Operating System, section 104.4: Runlevels and Boot Targets.
• Linux Essentials Topic 106: Security and File Permissions, section 106.1: Basic security and identifying user types.
• Linux Essentials Topic 106: Security and File Permissions, section 106.2: Creating users and groups.

CentOS is a Linux distribution that is based on the source code of Red Hat Enterprise Linux (RHEL). It is a free and open-source community-supported OS that provides an enterprise-level computing platform. CentOS is fully compatible with RHEL and can run the same applications and packages. Therefore, CentOS allows the team members to apply as much of their Red Hat Enterprise Linux knowledge as possible for their hobby project. References:

• Linux Essentials Version 1.6 Objectives1, Topic 1.1: Linux Evolution and Popular Operating Systems, Subtopic: Linux Distributions
• Linux Essentials Version 1.6 Exam Preparation Guide2, Section 1.1: Linux Evolution and Popular Operating Systems, Page 7
• CentOS Website3, About CentOS Linux
• Red Hat Enterprise Linux derivatives - Wikipedia4

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

These are the three most common service models offered by public cloud providers12. They differ in the level of abstraction and control they provide to the customers.

• Platform as a Service (PaaS) is a service model where the public cloud provider offers a ready-to-use platform for developing, testing, and deploying applications. The provider manages the underlying infrastructure, such as servers, storage, network, and operating system, while the customer only needs to focus on the application code andconfiguration. Examples of PaaS include Google App Engine, IBM Cloud Foundry, and Microsoft Azure App Service12.
• Infrastructure as a Service (IaaS) is a service model where the public cloud provider offers access to fundamental compute, network, and storage resources on demand over the public Internet or through dedicated connections. The provider manages the physical hardware and virtualization layer, while the customer has full control over the configuration and management of the virtual machines, operating system, and applications. Examples of IaaS include Google Compute Engine, IBM Cloud Virtual Servers, and Microsoft Azure Virtual Machines12.
• Software as a Service (SaaS) is a service model where the public cloud provider offers ready-to-use software applications that run on the provider’s infrastructure and are accessible through a web browser or a mobile app. The provider manages the entire software stack, including the infrastructure, platform, and application, while the customer only needs to pay for the usage or subscription of the service. Examples of SaaS include Google Workspace, IBM Watson, and Microsoft Office 36512.

References:

• What is Public Cloud | IBM
• What Is a Public Cloud? | Google Cloud