101-500 LPIC-1 Exam 101, Part 1 of 2, version 5.0 Questions and Answers

The /etc/yum.repos.d/ directory contains configuration files for additional yum repositories. Each file in this directory should end with .repo and contain information about one or more repositories. The yum command will read all the files in this directory and use them as sources for software packages. The format of the .repo files is similar to the /etc/yum.conf file, which contains the main configuration options for yum. Each .repo file can have one or more sections, each starting with [repository] where repository is a unique identifier for the repository. The section can have various options, such as name, baseurl, enabled, gpgcheck, etc. For example, a .repo file for the EPEL repository could look like this:

[epel] name=Extra Packages for Enterprise Linux 7 - $basearch baseurl=http://download.fedoraproject.org/pub/epel/7/$basearch enabled=1 gpgcheck=1 gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-EPEL-7

References:

• 2, 102.5 Use RPM and YUM package management
• 4, 101-500 Exam - Free Questions and Answers - ITExams.com
• man yum.conf

The world-writable directory that should be placed on a separate partition in order to prevent users from being able to fill up the / filesystem is /tmp. This directory is used by applications and users to store temporary files, and it is world-writable by default. By creating a separate partition for /tmp, the amount ofspace available to users is limited, and the root filesystem is protected from being filled up by temporary files1.

To create a separate partition for /tmp, you can use the fdisk or parted command to create a new partition on the disk. Once the partition is created, you can format it with a filesystem such as ext4, and then mount it to the /tmp directory using the mount command. Finally, you can modify the /etc/fstab file to ensure that the partition is mounted automatically at boot time1. Here is an example of the steps to create a separate partition for /tmp:

After completing these steps, the /tmp directory will be mounted on a separate partition, and users will be limited in the amount of space they can use for temporary files.

References:

• LFCS: Linux World-Writable Directory Partitioning

The yum command is a tool for managing software packages on Red Hat Enterprise Linux and other RPM-based systems. The yum update option will update the entire system by checking the versions of the installed packages and installing the latest available versions from the repositories. The yum upgrade option will do the same, but it will also remove any obsolete packages that are no longer needed by the system. Both options will prompt the user to confirm before proceeding with the update or upgrade process. References:

• Yum Command Cheat Sheet for Red Hat Enterprise Linux
• "yum update" Explained for Beginners!
• How to Install Updates on CentOS 7
• Which option to the yum command will update the entire system?

 The command that lists all currently installed packages when using RPM package management is rpm --query --all. This command displays information about all the packages that are currently installed on the system, including their name, version, release, and architecture1. The output can be customized by using various query options and format specifiers2.

The other commands are either invalid or related to YUM, not RPM. yum --query --all is not a valid YUM command, as YUM does not have a --query option3. yum --list --installed is a valid YUM command, but itlists the packages from the YUM repositories, not the RPM database3. rpm --list --installed is not a valid RPM command, as RPM does not have a --list option2.

References:

• RPM Command in Linux | Linuxize
• rpm(8) - Linux manual page
• Linux package management with YUM and RPM | Enable Sysadmin

 The command apt-cache can be used to perform a full text search on all available packages on a Debian system. It searches the package names and the descriptions for an occurrence of the regular expression given as a keyword and prints out the package name and the short description1. The syntax is: apt-cache search keyword. For example, apt-cache search openssh will return a list of packages related to OpenSSH2. The other commands are not suitable for this task because:

• apt is a high-level command-line tool that provides a user-friendly way to manage packages, but it does not have a search option3.
• apt-get is a low-level command-line tool that handles the installation and removal of packages, but it does not have a search option4.
• apt-search is not a valid command.
• dpkg is a tool to install, build, remove and manage Debian packages, but it does not have a search option5. It can only list the installed packages with the option -l4. References:
• How To Search For Available Packages From Command Line In Debian, Ubuntu Or Linux Mint [APT] - Linux Uprising Blog
• apt(8) — apt — Debian buster — Debian Manpages
• How to List Installed Packages on Debian | Linuxize
• Debian / Ubuntu Linux search package names with apt-cache command
• dpkg(1) — dpkg — Debian buster — Debian Manpages

 The RPM command that will output the name of the package which supplied the file /etc/exports is rpm -qf /etc/exports. This command will query the RPM database and find the package that owns or provides the file /etc/exports1. The output will show the package name, version, release, and architecture. For example:

The other options are incorrect for the following reasons:

• rpm -F /etc/exports. This command will try to freshen or upgrade the package that contains the file /etc/exports, if it is already installed2. This command will not output the package name, but rather install the latest version of the package from a specified source. For example:

• rpm -Kl /etc/exports. This command is not valid, as RPM does not have a -Kl option. The -K option is used to verify the signatures of the RPM package files, not the installed files3. The -l option is used to list the files in a package, not to query the package name. For example:

• rpm -qp /etc/exports. This command will try to query the package information of the file /etc/exports, as if it was an RPM package file. This command will not output the package name, but rather an error message, as /etc/exports is not a valid RPM package file. For example:

• rpm -qi /etc/exports. This command will try to query the information of the package /etc/exports, as if it was an installed package name. This command will not output the package name, but rather an error message, as /etc/exports is not a valid package name. For example:

References:

• How to find which rpm package provides a specific file or library in RHEL / CentOS
• rpm(8) - Linux manual page
• rpm(8) - Linux manual page
• [rpm(8) - Linux manual page]

The environment variable that overrides or extends the list of directories holding shared libraries is LD_LIBRARY_PATH. This variable is used to specify a colon-separated list of directories where the dynamic linker should look for shared libraries when loading a program1. The directories in LD_LIBRARY_PATH are searched before the default directories, such as /lib and /usr/lib, or the directories specified in/etc/ld.so.conf or the executable’s rpath1. This variable can be useful for testing or debugging purposes, or for running programs that require a specific version of a library that is not installed in the system1.

The other options are incorrect for the following reasons:

• LD_LOAD_PATH. This is not a standard environment variable for shared libraries. It may be confused with LD_PRELOAD, which is a variable that allows the user to specify one or more shared libraries that should be loaded before any other library, even the C library2. This variable can be used to override or modify the behavior of certain functions or symbols in the libraries2.
• LD_LIB_PATH. This is not a standard environment variable for shared libraries. It may be confused with LIBPATH, which is a variable that is used on some Unix variants, such as AIX, to specify the search path for shared libraries3. On Linux, this variable has no effect4.
• LD_SHARE_PATH. This is not a standard environment variable for shared libraries. It may be confused with LD_RUN_PATH, which is a variable that allows the user to specify a list of directories that should be embedded in the executable as the rpath5. The rpath is a attribute that tells the dynamiclinker where to look for shared libraries at run time5. Unlike LD_LIBRARY_PATH, LD_RUN_PATH is only effective at link time, not at run time5.
• LD_RUN_PATH. This is not an environment variable that overrides or extends the list of directories holding shared libraries, but rather one that sets the rpath of the executable at link time. See the explanation for LD_SHARE_PATH above.

References:

• How to set the environmental variable LD_LIBRARY_PATH in Linux
• LD_PRELOAD - The secret of code injection into a running process without ptrace
• LIBPATH - Wikipedia
• linux - What is the difference between LD_LIBRARY_PATH and -L at link time? - Stack Overflow
• ld-linux(8) - Linux manual page

The /etc/apt/sources.list file is the main configuration file for the Advanced Package Tool (apt), which is used to manage Debian installation package files. This file contains a list of repositories, or sources, from which apt can download and install packages. Each repository is specified by a line that has the following format:

type uri suite [component1] [component2] […]

Where:

• type is the access method, such as http, ftp, file, etc.
• uri is the Uniform Resource Identifier (URI) of the repository, such as http://deb.debian.org/debian
• suite is the distribution code name or archive name, such as stable, testing, unstable, etc.
• component is an optional section of the repository, such as main, contrib, non-free, etc.

For example, a typical sources.list file for Debian stable could look like this:

deb http://deb.debian.org/debian stable main contrib non-free deb-src http://deb.debian.org/debian stable main contrib non-free

deb http://deb.debian.org/debian-security/ stable/updates main contrib non-free deb-src http://deb.debian.org/debian-security/ stable/updates main contrib non-free

deb http://deb.debian.org/debian stable-updates main contrib non-free deb-src http://deb.debian.org/debian stable-updates main contrib non-free

The first two lines specify the main repository for Debian stable, with both binary (deb) and source (deb-src) packages. The next two lines specify the security updates repository for Debian stable, which contains important security fixes. The last two lines specify the stable-updates repository, which contains packages that have been updated after the release of Debian stable.

By editing the /etc/apt/sources.list file, one can select the network locations from which Debian installation package files are loaded. However, it is recommended to use a graphical or command-line tool, such as aptitude or synaptic, to manage the sources.list file, as they can handle the syntax and avoid errors.

References:

• 1, 102.4 Lesson 1
• 2, 102.4 Use Debian package management
• man sources.list

The command dpkg-reconfigure is a Debian package management tool that asks the configuration questions for a specific already installed package just as if the package were being installed for the first time. It can be used to reconfigure a package that was previously installed with default settings, or to change the settings of a package that requires user input during installation. It can also be used to fix a broken configuration file or to restore the original configuration file of a package. References:

• Debian Reference: Chapter 2. Debian package management
• LPI Linux Essentials: 1.3 Package Management

 The main configuration file for GNU GRUB is grub.cfg, which is usually located in /boot/grub/ or /boot/grub2/ depending on the distribution. This file contains the menu entries for the boot loader, each with a title, a kernel image, an initrd image, and optional parameters. The grub.cfg file is not meant to be edited manually, as it is generated by the grub-mkconfig command, which reads the settings from /etc/default/grub and the scripts in /etc/grub.d/. The /etc/default/grub file contains the global options for GRUB, such as the default menu entry, the timeout, the theme, etc. The /etc/grub.d/ directory contains executable scripts that are run by grub-mkconfig to generate the menu entries for each operating system or kernel found on the system. For example, the script 10_linux generates the entries for the Linux kernels installed by the package manager, while the script 30_os-prober generates the entries for other operating systems detected on the system, such as Windows. To make changes to the GRUB configuration, one should edit the /etc/default/grub file and/or the scripts in /etc/grub.d/, and then run grub-mkconfig -o /boot/grub/grub.cfg to update the grub.cfg file. References:

• 2, 102.2 Install a boot manager
• 4, 102.2 Install a boot manager
• man grub-mkconfig

The /tmp directory should be on a separate partition if possible because it is world writable. This means that any user can create, modify, or delete files and directories in /tmp. This can pose a risk of filling up the / partition, which can cause system instability or failure. By having /tmp on a separate partition, we can limit the amount of disk space that can be used by temporary files and prevent users from affecting the / partition. The /tmp directory is also a common target for malicious attacks, so having it on a separate partition can improve the security and isolation of the system. The /tmp directory is one of the few directories that are world writable by default, according to the Filesystem Hierarchy Standard (FHS)1. The other directories that are usually world writable are /var/tmp and /var/lock, which are also used for temporary or lock files. However, these directories are not as frequently used or as large as /tmp, so they are less likely to fill up the / partition. The /tmp directory also has the sticky bit set, which means that only the owner of a file or directory can delete or rename it2. This prevents users from deleting or modifying other users’ files in /tmp. However, this does not prevent users from creating new files or directories in /tmp, which can still consume disk space and resources. Therefore, it is advisable to have /tmp on a separate partition if possible. References:

• Filesystem Hierarchy Standard
• Sticky bit - Wikipedia

 The command df displays the current disk space usage for all mounted file systems. It shows the size, used space, available space, percentage of usage, and mount point of each file system. By default, the output is in 1K blocks, but it can be changed with options like -h (human-readable), -B (block size), -i (inodes), and -T (type). The command df is part of the 101.1 Determine and configure hardware settings topic of the LPI Linux Essentials certification program12. References:

• Linux Essentials - Linux Professional Institute Certification Programs1
• Exam 101 Objectives - Linux Professional Institute

The command that prints a list of usernames (first column) and their primary group (fourth column) from the /etc/passwd file is cut -d : -f 1,4 /etc/passwd. The cut command is used to extract selected fields or characters from each line of a file or standard input. The -d or --delimiter option specifies the character that separates the fields, which in this case is a colon (:). The -f or --fields option specifies the fields to be printed, which in this case are the first and the fourth fields. The /etc/passwd file is a text file that contains information about the user accounts on the system, such as the username, password, user ID, group ID, home directory, and login shell. The first column of the file is the username and the fourth column is the group ID, which corresponds to the primary group of the user. The cut command will print these two columns separated by a colon for each line of the file. For example, running cut -d : -f 1,4 /etc/passwd will produce an output like this:

root:0 daemon:1 bin:1 sys:3 sync:4 games:5 man:12 lp:7 mail:8 news:9 uucp:10 proxy:13 www-data:33 backup:34 list:38 irc:39 gnats:41 nobody:65534 systemd-network:100 systemd-resolve:101 syslog:102 messagebus:103 _apt:104 lxd:105 uuidd:106 dnsmasq:107 sshd:108 pollinate:109 vboxadd:999 ubuntu:1000

The other commands are either invalid or do not perform the desired task. The fmt command is used to reformat paragraphs of text, but it does not have a -f option. The sort command is used to sort lines of text, but it does not have a -t option. The paste command is used to merge lines of files, but it does not have a -f option. The split command is used to split a file into pieces, but it does not have a -c option. References:

• Linux Essentials - Linux Professional Institute Certification Programs
• Exam 101 Objectives - Linux Professional Institute
• cut(1) - Linux manual page
• /etc/passwd file - Linux.com

The directories on a 64 bit Linux system that typically contain shared libraries are /usr/lib64/ and /lib64/. Shared libraries are binary files that provide reusable functions, routines, classes, data structures, and so on for programs and applications. They are loaded into memory before the program starts and shared by multiple processes that use the same library. Shared libraries are usually stored in standard locations in the file system, such as /usr/lib, /usr/local/lib, /lib, and /lib64 for 32 bit systems, and /usr/lib64, /usr/local/lib64, /lib64, and /lib for 64 bit systems12. The /usr/lib64 and /lib64 directories contain the shared libraries for the system and user applications, respectively. The other directories are either non-existent or do not contain shared libraries. The ~/.lib64/ directory is not a standard location for shared libraries, and it is unlikely that a user would have such a directory in their home directory. The /var/lib64/ directory is also not a standard location for shared libraries, and it is usually used for variable data files that are specific to a package or application. The /opt/lib64/ directory is not a standard location for shared libraries, and it is usually used for optional software packages that are installed in the /opt directory3. References:

• Linux Essentials - Linux Professional Institute Certification Programs1
• Exam 101 Objectives - Linux Professional Institute2
• Understanding Shared Libraries in Linux - Tecmint3

The correct answer is A, tr -d ‘\r’ < userlist.txt > newlist.txt. This command will use the tr utility to delete the carriage return characters (\r) from the userlist.txt file and redirect the output to the newlist.txt file. The tr utility is used to translate, delete, or squeeze characters from the standard input and write the result to the standard output. The syntax of the tr command is:

tr [options] set1 [set2]

The options can modify the behavior of the tr command, such as complementing, squeezing, or truncating the sets of characters. The set1 and set2 are strings of characters that specify the translation to be performed. The characters in set1 are replaced by the corresponding characters in set2. If set2 is omitted, the characters in set1 are deleted.

The -d option tells tr to delete the characters in set1 from the output. The \r character is a special escape sequence that represents the carriage return character, which is used in Windows systems to mark the end of a line, along with the line feed character (\n). The < and > symbols are redirection operators that redirect the input and output of a command to a file or device. The < symbol redirects the standard input of a command from a file, while the > symbol redirects the standard output of a command to a file, overwriting any existing content.

Therefore, the command tr -d ‘\r’ < userlist.txt > newlist.txt will read each character from the userlist.txt file, delete any carriage return characters, and write the output to the newlist.txt file. This will effectively change all CR-LF line breaks (\r\n) in the userlist.txt file to Linux standard LF line breaks (\n) and store the result in newlist.txt.

The other commands are incorrect for the following reasons:

• B, tr -c ‘\n\r’ ‘’ userlist.txt: This command will not work as expected, because it has several errors. First, the -c option tells tr to complement the set of characters in set1, which means that the operations will apply to the characters that are not in the set1. However, the set1 in this command is ‘\n\r’, which includes both the line feed and the carriage return characters, so the complement will be all the other characters except these two. Second, the set2 in this command is an empty string (‘’), which means that tr will delete the characters that match the set1 (or its complement, in this case). Third, the redirection operators are reversed, which means that tr will read the input from the newlist.txt file and write the output to the userlist.txt file, instead of the other way around. Therefore, the command tr -c ‘\n\r’ ‘’ userlist.txt will delete all the characters except the line feed and the carriage return characters from the newlist.txt file and overwrite the userlist.txt file with the output, which will be a series of blank lines.
• C, tr ‘\r\n’ ‘’ newlist.txt: This command will not work as expected, because it has several errors. First, the set1 in this command is ‘\r\n’, which means that tr will match the carriage return and the line feed characters separately, not as a pair. Second, the set2 in this command is an empty string (‘’), which means that tr will delete the characters that match the set1. Third, the redirection operators are missing, which means that tr will not read the input from the userlist.txt file or write the output to the newlist.txt file, but instead it will expect the input from the standard input and write the output to the standard output. Therefore, the command tr ‘\r\n’ ‘’ newlist.txt will delete all the carriage return and the line feed characters from the standard input and write the output to the standard output, and treat the userlist.txt and newlist.txt as additional arguments that will cause an error.
• D, tr ‘\r’ ‘\n’ userlist.txt newlist.txt: This command will not work as expected, because it has several errors. First, the set1 and set2 in this command are ‘\r’ and ‘\n’, which means that tr will replace the carriage return characters with the line feed characters, not delete them. Second, the redirection operators are missing, which means that tr will not read the input from the userlist.txt file or write the output to the newlist.txt file, but instead it will expect the input from the standard input and write the output to the standard output. Third, the userlist.txt and newlist.txt are treated as additional arguments that will cause an error. Therefore, the command tr ‘\r’ ‘\n’ userlist.txt newlist.txt will replace all the carriage return characters with the line feed characters from the standard input and write the output to the standard output, and report an error for the extra arguments.
• E, tr -s ‘/M/J/’ userlist.txt newlist.txt: This command will not work as expected, because it has several errors. First, the -s option tells tr to squeeze the repeated characters in set1 with a single occurrence, not delete them. Second, the set1 in this command is ‘/M/J/’, which is not a valid escape sequence for the carriage return and the line feed characters. The correct escape sequences are ‘\r’ and ‘\n’, respectively. Third, the redirection operators are missing, which means that tr will not read the input from the userlist.txt file or write the output to the newlist.txt file, but instead it will expect the input from the standard input and write the output to the standard output. Fourth, the userlist.txt and newlist.txt are treated as additional arguments that will cause an error. Therefore, the command tr -s ‘/M/J/’ userlist.txt newlist.txt will squeeze the repeated occurrences of the characters /, ^, M, and J from the standard input and write the output to the standard output, and report an error for the extra arguments.

References:

• Tr Command in Linux with Examples | Linuxize
• tr command in Unix/Linux with examples - GeeksforGeeks
• How to Use the Linux tr Command - How-To Geek
• [tr(1) - Linux manual page - man7.org]
• [Linux tr command help and examples - Computer Hope].

The configuration of yum can be divided into multiple files, and repository configurations can include variables such as $basearch or $releasever. The main configuration file for yum is /etc/yum.conf, which contains the global options for yum and can also define repositories in the [repository] sections. However, it is recommended to define individual repositories in separate files in the /etc/yum.repos.d/ directory, which can be easier to manage and maintain. Each file in this directory should have a .repo extension and contain one or more [repository] sections with the repository name, URL, and other options12. Repository configurations can use yum variables to dynamically set values for certain options, such as the baseurl or the enabled. Yum variables are enclosed in curly braces and start with a dollar sign, such as {$basearch} or {$releasever}. These variables are replaced by their actual values at runtime, based on the system architecture, the operating system version, or other factors. Some of the common yum variables are34:

• $basearch: The base architecture of the system, such as x86_64, i386, or arm.
• $releasever: The release version of the operating system, such as 7, 8, or 9.
• $arch: The exact architecture of the system, such as x86_64, i686, or armv7hl.
• $uuid: A unique identifier for the system, generated by the product-id plugin.
• $YUM0-$YUM9: Custom variables that can be set by the user in the /etc/yum/vars/ directory or the /etc/yum.conf file.

The other options are false or irrelevant. There is no yum confupdate command or yumd service, and changes to the yum configuration become active immediately after saving the files. The /etc/yum.conf file is not ignored if the /etc/yum.repos.d/ directory contains files, but the repository options in the /etc/yum.conf file can be overridden by the options in the .repo files. References:

• Linux Essentials - Linux Professional Institute Certification Programs1
• Exam 101 Objectives - Linux Professional Institute2
• How to Use Yum Variables to Enhance your Yum Experience - Red Hat …3
• Yum Variables - CentOS4

The reserved space is a portion of the filesystem that is only accessible to the root user or users with sudo privileges. The reserved space serves two purposes: to prevent ordinary users from filling up the filesystem completely and crashing the system, and to reduce fragmentation by leaving some free space. The reserved space is set by default to 5% of the total filesystem size when the filesystem is created with the mkfs.ext4 command. This means that 5% of the blocks are reserved for the root user and are not counted as available space by the df command. The reserved space can be changed or disabled by using the tune2fs command with the -m option. For example, to change the reserved space to 1%, use the following command:

sudo tune2fs -m 1 /dev/sdXY

where /dev/sdXY is the device name of the ext4 filesystem.

To disable the reserved space completely, use 0% instead of 1%. However, this is not recommended, as it may affect the performance and stability of the system, especially if the filesystem is almost full.

References:

• Reserved space for root on a filesystem - why?
• Linux : How to reduce the percentage of reserved blocks on ext4 filesystem
• tune2fs(8) - Linux manual page

This command will display the output of the foo command on the screen and also write it to a file called /tmp/foodata. The syntax of the command is:

foo | tee [options] [file]

The foo command is any command that produces some output. The | symbol is a pipe operator that redirects the standard output of one command to the standard input of another command. The tee command reads from the standard input and writes to both the standard output and one or more files. The options can modify the behavior of the tee command, such as appending to the file instead of overwriting it, or ignoring interrupt signals. The file is the name of the file to which the output is written. If no file is given, the tee command will only write to the standard output.

Therefore, the command foo | tee /tmp/foodata will run the foo command, pipe its output to the tee command, which will display the output on the screen and write it to the file /tmp/foodata.

The other commands are incorrect for the following reasons:

• A, foo | less /tmp/foodata: This command will not write the output of the foo command to a file, but it will display the output of the foo command on the screen in a pager. The less command is a program that allows the user to view and scroll through a file or the output of a command. The syntax of the command is:

foo | less [options] [file]

The foo command is any command that produces some output. The | symbol is a pipe operator that redirects the standard output of one command to the standard input of another command. The less command reads from the standard input or a file and displays it on the screen in a pager. The options can modify the behavior of the less command, such as setting the number of lines per screen, or searching for a pattern. The file is the name of the file to be viewed. If no file is given, the less command will read from the standard input.

Therefore, the command foo | less /tmp/foodata will run the foo command, pipe its output to the less command, which will display the output on the screen in a pager. However, the /tmp/foodata argument will be ignored by the less command, because it will read from the standard input instead of the file. The command will not write anything to the file /tmp/foodata.

• B, foo | cp /tmp/foodata: This command will not work as expected, because it has several errors. First, the cp command is not a valid command to write the output of a command to a file. The cp command is used to copy files or directories from one location to another. The syntax of the command is:

cp [options] source destination

The options can modify the behavior of the cp command, such as preserving the attributes of the files, or creating backups of the existing files. The source is the name of the file or directory to be copied. The destination is the name of the file or directory where the source is copied to.

Second, the pipe operator is not a valid way to redirect the output of a command to the cp command. The pipe operator redirects the standard output of one command to the standard input of another command. However, the cp command does not read from the standard input, but from the source argument. Therefore, the command foo | cp /tmp/foodata will run the foo command, pipe its output to the cp command, which will ignore the standard input and report an error for missing the destination argument. The command will not write anything to the file /tmp/foodata.

• C, foo > /tmp/foodata: This command will not display the output of the foo command on the screen, but it will write it to a file called /tmp/foodata. The > symbol is a redirection operator that redirects the standard output of a command to a file or device, overwriting any existing content. The syntax of the command is:

foo > file

The foo command is any command that produces some output. The > symbol redirects the standard output of the foo command to the file. The file is the name of the file to which the output is written.

Therefore, the command foo > /tmp/foodata will run the foo command, redirect its output to the file /tmp/foodata, and overwrite any previous content. The command will not display anything on the screen.

• E, foo > stdout >> /tmp/foodata: This command will not work as expected, because it has several errors. First, the stdout argument is not a valid file name or device name. The stdout is an abbreviation for the standard output, which is a stream that a program uses to write its output. However, the stdout is not a file or device that can be used as a destination for the redirection operator. Second, the >> symbol is a redirection operator that redirects the standard output of a command to a file or device, appending to any existing content. The syntax of the command is:

foo >> file

The foo command is any command that produces some output. The >> symbol redirects the standard output of the foo command to the file. The file is the name of the file to which the output is appended.

Therefore, the command foo > stdout >> /tmp/foodata will run the foo command, redirect its output to the stdout argument, which will cause an error, and then redirect its output again to the file /tmp/foodata, which will append the output to the file. The command will not display anything on the screen.

References:

• Linux Tee Command with Examples | Linuxize
• tee command in Linux with examples - GeeksforGeeks
• Linux tee command explained for beginners (6 examples) - HowtoForge
• Command Options and Examples of Tee Command in Linux - UbuntuPIT
• Linux tee Command Explained for Beginners (6 Examples) - Linux Handbook.

Systemd is a system and service manager for Linux systems, and it can manage the mounting and unmounting of file systems. Systemd can automatically create and start mount units for file systems that are listed in /etc/fstab or are known to the system. Mount units are unit files that encode information about a file system mount point controlled and supervised by systemd. Mount units must be named after the mount point directories they control, and they have the suffix .mount. For example, the mount point /home must be configured in a unit file home.mount.

Systemd can also handle file systems that are neither listed in /etc/fstab nor known to the system, but are mounted manually by the user. In this case, systemd automatically generates a transient mount unit and monitors the mount point without changing it. A transient mount unit is a unit that is created dynamically and temporarily, and is not backed by a unit file on disk. A transient mount unit has the same name and properties as a regular mount unit, but it is not persistent across reboots. Systemd does not interfere with the manual mount, and does not unmount it unless explicitly requested by the user. The user can use the mount command or the systemd-mount command to create a manual mount, and the umount command or the systemd-umount command to remove it. The user can also use the systemctl command to inspect and control the transient mount unit. For example, to show the status of the transient mount unit for the mount point /mnt, use the following command:

systemctl status mnt.mount

References:

• systemd.mount - freedesktop.org
• systemd-mount - freedesktop.org
• How to name systemd mount unit properly? - Server Fault
• Working with Systemd Mount Units - Pluralsight

The command that searches for packages owning the file /etc/debian_version is dpkg –S /etc/debian_version. The dpkg command is the low-level tool for installing, removing, configuring, and querying Debian packages. The -S or --search option takes a file name or a pattern as an argument and searches for the packages that contain the matching files. The output shows the package name and the file name separated by a colon. For example, running dpkg -S /etc/debian_version will produce the output base-files:/etc/debian_version, indicating that the file /etc/debian_version belongs to the base-files package. The other commands are either invalid or do not perform the desired task. The apt-get command is used to download and install packages from the Debian repositories, but it does not have a search option. The aptcommand is a high-level tool for managing packages, but it does not have a -r option. The find command is used to search for files in the file system, but it does not have a -dpkg option. The apt-file command is used to search for files in the packages available in the Debian repositories, but it requires a subcommand such as search or show before the file name or pattern. References:

• Linux Essentials - Linux Professional Institute Certification Programs1
• Exam 101 Objectives - Linux Professional Institute2
• dpkg(1) - Linux manual page3
• apt-get(8) - Linux manual page
• apt(8) - Linux manual page
• find(1) - Linux manual page
• apt-file(1) - Linux manual page

The umask value is a four-digit octal number that determines the default permissions for new files and directories created by a user. The umask value specifies the permissions that are not granted to the user, group, and others. The permissions are represented by three bits for each category, where 1 means execute, 2 means write, and 4 means read. The sum of these values indicates the combination of permissions. For example, 7 means read, write, and execute; 6 means read and write; 5 means read and execute; 4 means read only; 3 means write and execute; 2 means write only; 1 means execute only; and 0 means no permission.

The umask value is subtracted from the maximum permissions for files and directories, which are 666 and 777, respectively. The maximum permissions are then converted to binary and bitwise ANDed with the bitwise complement of the umask value. The result is the default permissions for the new files and directories. For example, if the umask value is 0027, the default permissions for a new file are:

666 - 027 = 639 639 in octal = 110 011 001 in binary 027 in octal = 000 010 111 in binary Bitwise complement of 027 = 111 101 000 in binary 110 011 001 AND 111 101 000 = 110 001 000 in binary 110 001 000 in binary = 608 in octal 608 in octal = rw- — —

The default permissions for a new directory are:

777 - 027 = 750 750 in octal = 111 101 000 in binary 027 in octal = 000 010 111 in binary Bitwise complement of 027 = 111 101 000 in binary 111 101 000 AND 111 101 000 = 111 101 000 in binary 111 101 000 in binary = 750 in octal 750 in octal = rwx r-x —

Therefore, the umask value of 0027 ensures that new files can be read and written by their owning user, and are not accessible at all for everyone else. New directories can be read, written and listed by their owning user, read and listed by their owning group, and are not accessible at all for everyone else.

References:

• Umask command in Linux with examples - GeeksforGeeks
• What Is umask in Linux, and How Do You Use It? - How-To Geek
• What is UMASK and how to set UMASK in Linux/Unix? - Kernel Talks

The command that lists the dependencies of the RPM package file foo.rpm is rpm -qpR foo.rpm. The rpm command is the low-level tool for managing RPM packages on Linux systems. The -q or --query option isused to query information about installed or uninstalled packages. The -p or --package option is used to specify a package file instead of an installed package name. The -R or --requires option is used to list the capabilities that the package requires. The capabilities are usually the names of other packages, libraries, or files that the package depends on. The rpm command is part of the 101.1 Determine and configure hardware settings topic of the LPI Linux Essentials certification program .

The other options are either invalid or do not perform the desired task. The rpm -dep foo command does not exist, as -dep is not a valid option for rpm. The rpm -ld foo.rpm command does not list the dependencies of the package file, but the files in the package. The rpm -R foo.rpm command does not list the dependencies of the package file, but the capabilities that the package provides. The rpm -pD foo command does not exist, as -pD is not a valid option for rpm. References:

• Linux Essentials - Linux Professional Institute Certification Programs
• Exam 101 Objectives - Linux Professional Institute
• rpm(8) - Linux manual page
• RPM Package Manager - Wikipedia

The mount --bind command is used to create a bind mount, which is an alternate view of a directory tree. A bind mount takes an existing directory tree and replicates it under a different point. The directories and files in the bind mount are the same as the original. Any modification on one side is immediately reflected on the other side, since the two views show the same data. For example, after issuing the command:

mount --bind /some/where /else/where

the directories /some/where and /else/where have the same content, which is the content of /some/where. A bind mount can be useful for accessing hidden files, creating chroot environments, or changing the permissions or ownership of files.

The other options are not correct because:

• B. It mounts all available filesystems to the current directory: This is not what the mount --bind command does. The mount --bind command only creates a bind mount for a single directory tree. To mount all available filesystems to the current directory, one would need to use the mount -a command with the -t option and specify the current directory as the target.
• C. It mounts all user mountable filesystems to the user’s home directory: This is not what the mount --bind command does. The mount --bind command only creates a bind mount for a single directory tree. To mount all user mountable filesystems to the user’s home directory, one would need to use the mount -a command with the -t option and specify the user’s home directory as the target. However, this is not a common or recommended practice, as it may cause conflicts or errors with the existing files and directories in the user’s home directory.
• D. It mounts all file systems listed in /etc/fstab which have the option userbind set: This is not what the mount --bind command does. The mount --bind command only creates a bind mount for a single directory tree. To mount all file systems listed in /etc/fstab which have the option userbind set, one would need to use the mount -a command with the -O option and specify userbind as the option. However, this is not a standard or supported option for the mount command or the /etc/fstab file, and it may not work as expected.
• E. It permanently mounts a regular file to a directory: This is not what the mount --bind command does. The mount --bind command only creates a bind mount for a directory tree, not a regular file. To mount a regular file to a directory, one would need to use the mount command with the -o loop option and specify the file and the directory as the source and the target. However, this is only possible for files that contain a valid filesystem image, such as an ISO file or a disk image. A bind mount is not permanent, and it can be unmounted with the umount command.

References:

• Understanding Bind Mounts | Baeldung on Linux
• What is a bind mount? - Unix & Linux Stack Exchange
• mount(8) - Linux manual page

The command that installs GRUB 2 into the master boot record on the third hard disk is grub-install /dev/sdc. The grub-install command is the high-level tool for installing GRUB 2 on a disk or a partition. It takes a device name as an argument and writes the GRUB 2 boot loader information to the specified location. If the device name is a disk, such as /dev/sdc, the boot loader information is written to the master boot record (MBR) of the disk, which is the first sector that contains the boot code and the partition table. If the device name is a partition, such as /dev/sdc1, the boot loader information is written to the boot sectorof the partition, which is the first sector of the partition that contains the boot code and the file system information. The grub-install command is part of the 101.1 Determine and configure hardware settings topic of the LPI Linux Essentials certification program12.

The other commands are either invalid or do not perform the desired task. The grub2 install command does not exist, as grub2 is not a valid command name. The grub-mkrescue command is used to create a bootable GRUB 2 rescue image, not to install GRUB 2 on a disk or a partition3. The grub-mbrinstall command does not exist, as mbrinstall is not a valid subcommand for grub. The grub-setup command is a low-level tool for installing GRUB 2 on a disk or a partition, but it is not recommended for normal use, as it requires specifying the location of the GRUB 2 core image file4. References:

• Linux Essentials - Linux Professional Institute Certification Programs1
• Exam 101 Objectives - Linux Professional Institute2
• GNU GRUB Manual 2.06: Making a GRUB bootable CD-ROM3
• GNU GRUB Manual 2.06: Installing GRUB natively4

 The daemon that handles power management events on a Linux system is acpid. A daemon is a background process that runs continuously and performs certain tasks without user intervention. The acpid daemon listens for power management related events, such as switching between AC and battery power on a laptop, pressing the power button, closing the lid, etc., and executes various commands in response. The acpid daemon can be configured by editing the files in /etc/acpi/events and /etc/acpi/actions directories, or by using a graphical tool like gnome-power-manager or xfce4-power-manager. The acpid daemon is part of the 101.1 Determine and configure hardware settings topic of the LPI Linux Essentials certification program12. References:

• Linux Essentials - Linux Professional Institute Certification Programs1
• Exam 101 Objectives - Linux Professional Institute2
• Power management - ArchWiki2
• 9.12. Power Management: Advanced Configuration and Power Interface (ACPI)

The regular expression that represents a single upper-case letter is [A-Z]. This is a character class that matches any one character from the range A to Z, which are the 26 upper-case letters of the English alphabet. A character class is enclosed in square brackets and can contain a list or a range of characters to match. For example, [abc] matches any one of the letters a, b, or c, and [0-9] matches any one digit from 0 to 9. The other options are not valid regular expressions for a single upper-case letter. The :UPPER: option is not a valid syntax for a character class, and it would be interpreted as a literal string of seven characters. The !a-z option is not a valid syntax for a negated character class, and it would be interpreted as a literal string of four characters. The %C option is not a valid syntax for a character class, and it would be interpreted as a literal string of two characters. The {AZ} option is not a valid syntax for a character class, and it would be interpreted as a literal string of four characters. The curly braces are used for interval expressions, which specify the number of repetitions of a character or a group of characters. For example, a{2,4} matches the letter a repeated two, three, or four times. References:

• How to Use Regular Expressions (regexes) on Linux1
• How to Use Regular Expressions (RegEx) on Linux2
• A beginner’s guide to regular expressions with grep3

The correct commands to create an ext3 filesystem on /dev/sdb1 are /sbin/mke2fs -j /dev/sdb1 and /sbin/mkfs -t ext3 /dev/sdb1. These commands format the partition /dev/sdb1 with the ext3 filesystem type. The first command uses the mke2fs utility with the -j option, which enables journaling. The second command uses the mkfs utility with the -t option, which specifies the filesystem type. Both commands are equivalent and can be used interchangeably. The other options are incorrect because they use the wrong syntax or parameters for the commands. Option C is wrong because the -c option for the mkfs command checks the device for bad blocks, not the filesystem type. Option D is wrong because there is no such utility as mke3fs. The correct utility name is mke2fs.

The modprobe command is used to add or remove modules from the Linux kernel. The modprobe command can automatically resolve and load the dependencies of a module, which are the other modules that the module depends on. The modprobe command reads the modules.dep file, which is generated by the depmod command, to determine the dependencies of a module. The syntax of the modprobe command is:

modprobe [options] module [module parameters]

The module is the name of the module to be loaded or removed. The module parameters are optional arguments that can modify the behavior of the module. The options are optional, and they can modify the behavior of the modprobe command, such as displaying the dependencies, listing the modules, or specifying the configuration file.

For example, to load the e1000e module, which is a driver for Intel Gigabit Ethernet adapters, along with any required dependency modules, use the following command:

modprobe e1000e

This command will load the e1000e module and any other modules that it depends on, such as the crc32c module. You can verify the loaded modules by using the lsmod command, which lists the modules and their dependencies, sizes, and usage counts.

The other options are not correct because:

• A. depmod: This command is used to generate the modules.dep file, which contains the dependency information for the modules. The depmod command does not load or remove any modules, but it prepares the modules.dep file for the modprobe command to use. The depmod command is usually run automatically when a new kernel or module is installed, and it does not need to be run manually by the user.
• B. insmod: This command is used to insert a single module into the kernel. The insmod command does not resolve or load any dependencies of the module, and it requires the full path to the module file as an argument. The insmod command is a low-level command that is rarely used by the user, and it is usually invoked by the modprobe command internally.
• D. module_install: This command does not exist in the Linux system. There is no such command as module_install in the Linux documentation or the man pages.
• E. loadmod: This command does not exist in the Linux system. There is no such command as loadmod in the Linux documentation or the man pages.

References:

• modprobe(8) - Linux manual page
• How to Load and Unload Kernel Modules in Linux - Linux Handbook
• Linux Kernel Module Programming Guide - TLDP

 The correct file permissions that belong to a symbolic link are lrwxrwxrwx. This is because a symbolic link is a special file that points to another file or directory. The first character of the file permissions indicates the file type. The letter l means that the file is a symbolic link. The other letters r, w, and x represent the read, write, and execute permissions for the owner, group, and others classes. However, the permissions of the symbolic link are not used for accessing the file or directory that it points to. The permissions of the target file or directory are used instead. Therefore, the permissions of the symbolic link are usually set to rwx for all classes, meaning that anyone can read, write, or execute the link. The other options are incorrect because they do not indicate the file type of a symbolic link. Option A is wrong because the first character - means that the file is a regular file, not a symbolic link. Option B is wrong because the first character + is not a valid file type indicator. Option D is wrong because the first character s means that the file is a socket, not a symbolic link. References:

• symlink - Change permissions for a symbolic link - Unix & Linux Stack Exchange
• linux - How do file permissions apply to symlinks? - Super User
• Is it possible to change the permissions for the symbolic link?
• Permission through symbolic link - Unix & Linux Stack Exchange
• How to change permissions for a symbolic link under Linux/UNIX

The command yum check-update prints a list of available package updates when using RPM-based package management. This command queries all enabled repositories and shows the packages that have updates available, along with the new version number. This command does not actually update any packages, but only lists them. To update the packages, the command yum update can be used. The other commands are either invalid or belong to a different package management system. dpkg is a low-level tool for Debian-based package management, and yum list shows all available packages in the repositories, not just the ones that have updates. References:

• Linux Package Management with Yum, RPM, Apt, Dpkg, Aptitude and Zypper - Part 9
• rpm - RPM package management tool | Linux Docs
• RPM Command in Linux | Linuxize

The command rpm -qpl apache-ql.rpm is used to preview the list of files that would be installed by the RPM package file apache-xml.rpm. This command queries the package file without installing it and lists the contents of the package. Here’s what each part of the command means:

• rpm is the command-line tool used for managing RPM packages on Linux systems.
• -qpl are options for the rpm command.
• apache-xml.rpm is the name of the RPM package file you want to query.

So, when you run this command, it will display a list of all the files that are included in the apache-xml.rpm package file, without installing it. This can be useful for checking what files are included in the package before installing it or comparing it with another version of the package.

The other commands are either invalid or do not perform the same function as the correct answer. For example:

• rpm -qp apache-xml.rpm will only display the name and version of the package, not the list of files.
• rpm -qv apache-xml.rpm will display the verbose information about the package, such as the description, license, and changelog, but not the list of files.
• rpm -ql apache-xml.rpm will list the files that are installed on the system by the apache-xml.rpm package, but only if the package is already installed. If the package is not installed, it will return an error.

References:

• 4 ways to list files within a rpm package in Linux
• How to list all files installed by RPM package
• How to List Files Installed From an RPM Package in CentOS?
• How to list all files contained in an RPM package

The BIOS (Basic Input/Output System) is a firmware program that is stored in a ROM chip on the motherboard, and it performs some basic tasks when the system is powered on, such as:

• initializing the hardware components and peripherals
• performing the power-on self-test (POST) to check the system integrity
• selecting a boot device from the boot order list
• loading and executing the bootloader program from the boot device

The boot device is the data carrier that contains the bootloader, which is a small program that is responsible for loading and executing the kernel. The boot device can be a hard disk, a USB drive, a CD-ROM, or a network device. The BIOS has a boot order list, which is a sequence of possible boot devices that the BIOS will search for a valid bootloader. The boot order list can be configured by the user through the BIOS setup utility, which is usually accessed by pressing a key such as F2, F10, or Del during the POST.

The BIOS will search for a bootloader by means of a special signature, which is a sequence of bytes that indicates the presence of a bootloader. The signature is usually located in the first sector of the boot device, which is called the boot sector or the master boot record (MBR). The BIOS will read the boot sector of each boot device in the boot order list, and check if the last two bytes are 0x55 and 0xAA, which are the standard boot signature. If the boot signature is found, the BIOS will load the boot sector into memory and execute it. If the boot signature is not found, the BIOS will move on to the next boot device in the boot order list. If none of the boot devices have a valid boot signature, the BIOS will display an error message such as:

No bootable device – insert boot disk and press any key

References:

• How does the BIOS know where the bootloader is located? - Super User
• Bootloader: What is it and how does it work? - IONOS
• Boot Process with Systemd in Linux - GeeksforGeeks
• Linux Boot Process Step-by-Step Explained - javatpoint

The tune2fs command is used to change metadata and options for ext2, ext3, and ext4 filesystems. The tune2fs command can adjust various parameters such as the maximum mount count, the check interval, the reserved blocks percentage, the volume label, and the UUID. The tune2fs command can also enable or disable some filesystem features, such as the journal, the dir_index, the acl, and the user_xattr. The tune2fs command requires the device name or the UUID of the filesystem as an argument, and one or more options to specify the changes to be made. For example, to change the volume label of an ext3 filesystem on /dev/sda1 to “data”, use the following command:

tune2fs -L data /dev/sda1The other options are not valid commands or options. The mod3fs and mod2fs commands do not exist on a standard Linux system. The tune3fs command is a synonym for tune2fs, but it is not commonly used. The dump2fs command is used to display the superblock and blocks group information for ext2, ext3, and ext4 filesystems, but it does not change any parameters or options. References:

• tune2fs - adjust tunable filesystem parameters on ext2/ext3/ext4 …
• Chapter 5. The Ext3 File System - Red Hat Customer Portal
• Chapter 37. Getting started with an ext3 file system - Red Hat Customer …

A hard link is a directory entry that refers to the same inode as another file. An inode is a data structure that stores the metadata and the location of the data blocks of a file. A hard link allows multiple names to refer to the same file content, as long as they are on the same filesystem. Therefore, when a hard link is created, the inode reference count is increased by one, and when a hard link is deleted, the inode reference count is decreased by one. The file content is only removed from the disk when the inode reference count reaches zero, meaning that there are no more hard links to the file. In this scenario, after successfully creating a hard link called bar to the ordinary file foo, foo and bar both refer to the same inode and the same file content. The inode reference count is two. When foo is deleted from the filesystem, the inode reference count is decreased by one, but it is still one, meaning that there is still one hard link to the file. Therefore, foo would be removed while bar would remain accessible. The file content would not be removed from the disk until bar is also deleted. The other options are either incorrect or not applicable. The user is not prompted whether bar should be removed, too. The bar link would still exist and be usable, not unusable. References:

• LPIC-1 Exam 101 Objectives, Topic 103: GNU and Unix Commands, 103.3 Perform basic file management
• LPIC-1 Linux Administrator 101-500 Exam FAQ, LPIC-1 Exam 101 Objectives, GNU and Unix Commands (Total Weight: 25)

When piping the output of find to the xargs command, the option to find that is useful if the filenames have spaces in them is -print0. The -print0 option prints the full file name on the standard output (STDOUT), followed by a null character, instead of a newline. This allows the xargs command to use the -0 option to read items from the standard input (STDIN) delimited by null characters, instead of spaces or newlines. This way, filenames with spaces are not split into separate arguments. For example, find . -name “*.txt” -print0 | xargs -0 grep “hello” will find all the text files in the current directory and its subdirectories that contain the word hello, even if the filenames have spaces in them. The -rep-space, -nospace, and -ignore-space options are not valid options for the find command. References: LPI Exam 101 Detailed Objectives, Topic 103: GNU and Unix Commands, Weight: 25, Objective 103.3: Perform basic file management, find command, xargs command

The Filesystem Hierarchy Standard is a distribution neutral description of locations of files and directories. According to the first result, it is a reference describing the conventions used for the layout of Unix-like systems. It is maintained by the Linux Foundation and the latest version is 3.0

The mkfs command creates a file system on a given device partition. If the type of file system is not specified, the default file system type is ext2. This is mentioned in the man page of mkfs1 and also in the article by How-To Geek2. Ext2 is an older file system that does not support journaling, which is a feature that allows the file system to recover from crashes or power failures. Ext2 is not very commonly used nowadays, as most Linux systems prefer ext4 or other file systems that support journaling and other features. References:

• How to Use the mkfs Command on Linux - How-To Geek
• mkfs(8): build file system - Linux man page

 The signal that is sent by the kill command by default is SIGTERM(15). The kill command sends a signal to a process to terminate it. The signal can be specified by name or number as an option to the kill command. If no signal is specified, the default signal is SIGTERM(15), which means terminate. The process can catch this signal and perform any necessary cleanup before exiting. The SIGHUP(1) signal means hang up and is usually sent when the terminal or network connection is disconnected. The SIGQUIT(3) signal means quit and is usually sent when the user presses Ctrl-\ on the keyboard. The SIGKILL(9) signal means kill and is used to force the process to terminate immediately, without any chance to catch the signal or perform any cleanup. References: LPI Exam 101 Detailed Objectives, Topic 103: GNU and Unix Commands, Weight: 25, Objective 103.3: Perform basic file management, kill command, Signal List

The system configuration file named /etc/inittab is commonly used to set the default runlevel. This file contains information about the initialization process of the system, and it defines the default runlevel, the available runlevels, and the actions to be taken when entering or leaving a runlevel. The default runlevel is the mode of operation that the system starts up into, and it determines which services and processes are running. The default runlevel is specified by a line similar to the following in the /etc/inittab file:

id:5:initdefault:

The number after the first colon indicates the default runlevel, which can range from 0 to 6. The meaning of each runlevel is:

• 0 — Halt
• 1 — Single-user text mode
• 2 — Not used (user-definable)
• 3 — Full multi-user text mode
• 4 — Not used (user-definable)
• 5 — Full multi-user graphical mode (with an X-based login screen)
• 6 — Reboot

To change the default runlevel, edit the /etc/inittab file as root and change the number to the desired runlevel. For example, to change the default runlevel to 3, use the following command:

sudo nano /etc/inittab

And change the line to:

id:3:initdefault:

Then save and exit the file. The changes will take effect on the next reboot.

References:

• SysV Init Runlevels - Red Hat Customer Portal
• init - How can I see or change default run level? - Ask Ubuntu

The correct commands to display all currently mounted filesystems are cat /proc/self/mounts and mount. The cat /proc/self/mounts command reads the contents of the /proc/self/mounts file, which is a symbolic link to /proc/mounts. This file contains information about all the filesystems that are currently mounted on the system, as reported by the kernel. The mount command without any arguments shows all the mounted filesystems, as recorded by the mount and umount commands. The other options are incorrect because they do not display the mounted filesystems. The free command shows the amount of free and used memory in the system. The lsmounts command is not a standard Linux command. The cat /proc/filesystems command shows the filesystem types that are supported by the kernel. References:

• [LPI Linux Essentials - 2.2 Mounting, Unmounting Filesystems]
• How to get the complete and exact list of mounted filesystems in Linux? - Unix & Linux Stack Exchange
• 4 Commands to List Mounted File Systems in Linux - Linux Shell Tips
• How To Show Mounted Devices In Linux Operating System
• How to Check if a Filesystem is Mounted in Linux?

The correct answers are C and E. Instead of supplying an explicit device in /etc/fstab for mounting, you can also use LABEL or UUID to identify the intended partition. LABEL is a human-readable name that can be assigned to a partition using tools such as e2label, tune2fs, or gparted. UUID is a universally unique identifier that is automatically generated for each partition and can be obtained using tools such as blkid or lsblk. Using LABEL or UUID instead of device names can be useful for avoiding problems caused by device name changes, such as when adding or removing disks. For example, instead of writing something like this in /etc/fstab:

/dev/sda1 /mnt/example ext4 defaults 0 0

You can write something like this:

LABEL=example /mnt/example ext4 defaults 0 0

or

UUID=80b496fa-ce2d-4dcf-9afc-bcaa731a67f1 /mnt/example ext4 defaults 0 0

The other options are not valid ways to identify a partition in /etc/fstab. FIND, ID, and NAME are not supported by the mount command or the /etc/fstab file. For more information on how to use LABEL and UUID in /etc/fstab, you can refer to the following articles:

• How to Use UUID to Mount Partitions / Volumes Under Ubuntu Linux
• How to Use Labels and UUIDs to Mount Partitions in Linux
• How to use disk quota on Linux with examples
• How to use UUIDs in fstab - LinuxConfig.org

The .bash_history file, located in the user home directory, is used to store the Bash history. The Bash history is a list of commands that the user has entered in the Bash shell. The .bash_history file is created when the user first starts a Bash session, and is updated when the user exits the session or runs the history command with the -a or -w option. The user can view the contents of the .bash_history file with the cat command, or use the history command to see the numbered list of commands. The user can also edit, delete, or clear the .bash_history file with various commands and options. The location and name of the history file can be changed by setting the HISTFILE environment variable to a different value. References:

• [LPI Exam 101 Detailed Objectives], Topic 103: GNU and Unix Commands, Objective 103.1: Work on the command line, Weight: 4, Key Knowledge Areas: Use of history and HISTFILE.
• Where is bash’s history stored?, Topic: Bash maintains the list of commands internally in memory while it’s running.

QUESTIONNO: 26

Which Bash environment variable defines in which file the user history is stored when exiting a Bash process? (Specify ONLY the variable name.)

Answer: HISTFILE

The HISTFILE environment variable defines in which file the user history is stored when exiting a Bash process. The user history is a list of commands that the user has entered in the Bash shell. By default, the HISTFILE variable is set to ~/.bash_history, which means that the history is stored in a hidden file called .bash_history in the user’s home directory. The user can change the value of the HISTFILE variable to store the history in a different file or location. For example, the following command will set the HISTFILE variable to ~/my_history:

export HISTFILE=~/my_history

This will cause the history to be stored in a file called my_history in the user’s home directory. The user can also unset the HISTFILE variable to disable the history saving feature. For example, the following command will unset the HISTFILE variable:

unset HISTFILE

This will prevent the history from being written to any file when the Bash process exits. The user can view the value of the HISTFILE variable by using the echo command. For example, the following command will display the value of the HISTFILE variable:

echo $HISTFILE

The output will be something like:

/home/user/.bash_history

References:

• [LPI Exam 101 Detailed Objectives], Topic 103: GNU and Unix Commands, Objective 103.1: Work on the command line, Weight: 4, Key Knowledge Areas: Use of history and HISTFILE.
• How To Read and Set Environmental and Shell Variables on Linux, Topic: How the Environment and Environmental Variables Work.

The uptime and top commands can be used to determine how long the system has been running. The uptime command displays the current time, the system load, the number of users logged in, and the time since the system was last booted. The top command displays information about the processes running on the system, as well as the system load, the number of users logged in, and the time since the system was last booted. The other options are either invalid or do not perform the desired task. The up command is not a valid Linux command. The uname -u command displays the user ID of the current user, not the system uptime. The time –up command is not a valid syntax for the time command, which measures the execution time of a command, not the system uptime. References:

• LPIC-1 Exam 101 Objectives, Topic 103: GNU and Unix Commands, 103.2 Process management
• LPIC-1 Linux Administrator 101-500 Exam FAQ, LPIC-1 Exam 101 Objectives, GNU and Unix Commands (Total Weight: 25)

The tr command is used to translate or delete characters from a given input. The -d option specifies that the characters in the second argument should be deleted from the input. In this case, the second argument is aieou, which are the vowels in the English alphabet. Therefore, the tr command will delete any vowel from the input, which is Hello World. The output will be the input without any vowels, which is Hll Wrld. References:

• [LPI Exam 101 Detailed Objectives], Topic 103: GNU and Unix Commands, Objective 103.7: Perform basic file management, Weight: 4, Key Knowledge Areas: Use of tr to perform basic text transformations.
• [LPI Linux Essentials Certification All-in-One Exam Guide], Chapter 5: Working with Files, Page 165, Using the tr Command.

The cut command is used to extract sections from each line of a file or input stream. The -d option specifies the delimiter that separates the fields in each line. The -f option specifies the fields to select. In this case, the delimiter is a colon (:) and the fields are 1 and 7. The first field is the user name and the seventh field is the login shell. Therefore, the cut command with these options will generate a list of user names and their login shells from /etc/passwd. References:

• Linux cut Command Explained with 6 Examples
• How to Use the Linux cut Command
• cut command in Linux with examples

 The commands that directly execute the instruction from the file /usr/local/bin/runme.sh without starting a subshell are source /usr/local/bin/runme.sh and . /usr/local/bin/runme.sh. These commands use the source or dot builtins, which read and execute commands from the given file in the current shell environment. This means that any changes made by the file, such as setting variables, defining functions, or changing directories, will affect the current shell. This is different from running the file as a script, which will create a new shell process and execute the commands in a separate environment. The source or dot commands are useful for loading configuration files, such as ~/.bashrc or /etc/profile, or for running scripts that modify the current state of the shell.

The other commands are incorrect for the following reasons:

• C. /bin/bash /usr/local/bin/runme.sh: This command will run the file as a script using the /bin/bash interpreter. This will create a new shell process and execute the commands in a separate environment. Any changes made by the file will not affect the current shell.
• D. /usr/local/bin/runme.sh: This command will also run the file as a script, but using the interpreter specified by the shebang line (#!) at the beginning of the file. If the file does not have a shebang line, it will use the default shell interpreter, which may or may not be /bin/bash. This will also create a new shell process and execute the commands in a separate environment. Any changes made by the file will not affect the current shell.
• E. run /usr/local/bin/runme.sh: This command is not valid, as there is no builtin or external command called run. This will produce an error message.

References:

• [LPI Exam 101 Detailed Objectives], Topic 103: GNU and Unix Commands, Objective 103.1: Work on the command line, Weight: 4, Key Knowledge Areas: Use of source and ..
• [Bash Reference Manual], Section 4.2: Bash Builtin Commands, Subsection 4.2.5: Bourne Shell Builtins.

In the vi editor, one of the ways to issue commands multiple times or apply them to multiple rows is to specify the number right in front of a command. This will repeat the command as many times as the number indicates. For example, the command 4l will move the cursor four characters to the right, and the command 2yj will copy two lines from the current line to the buffer. This method can be used for most of the vi commands that operate on single characters, words, lines, or blocks of text. Another way to issue commands multiple times or apply them to multiple rows is to use the . (dot) command, which repeats the last command. For example, after deleting a line with dd, pressing . will delete another line. However, this method is less precise and efficient than specifying the number before the command. References:

• Basic vi commands (cheat sheet), Topic: Moving within a File (Navigation).
• Vi Editor with Commands in Linux/Unix Tutorial, Topic: VI Editing commands.

The bg command is used to resume a suspended command in the background, allowing it to run without user interaction. The command takes a job ID as an argument, which can be obtained by using the jobs command. Alternatively, if no job ID is specified, bg will resume the most recently suspended job. The bg command is part of the job control features of the Linux shell, which allow users to manage multiple processes running in the same terminal. References:

• LPI Linux Essentials: 1.3.2 Job Control
• LPI Linux Administrator: 103.1 Work on the command line

 The command that displays the contents of a gzip compressed tar archive is tar ztf archive.tgz. This command uses the following options:

-z: Tells tar to read or write archives through gzip, allowing it to work on compressed files directly. -t: Lists the contents of an archive without extracting it. -f archive.tgz: Specifies the name of the archive file.

The output of this command will show the names of the files and directories stored in the archive, one per line. For example, if the archive contains three files named file1, file2, and file3, the output will be:

file1 file2 file3

The other commands are incorrect for the following reasons:

• gzip archive.tgz | tar xvf -: This command will decompress the archive using gzip and pipe it to tar, which will extract the files to the current directory. The - option tells tar to read the archive from the standard input. This command does not display the contents of the archive, but rather extracts them.
• gzip -d archive.tgz | tar tvf -: This command is similar to the previous one, except that it uses the -d option for gzip to decompress the archive instead of compressing it, and the -t option for tar to list the contents instead of extracting them. However, this command is redundant and inefficient, as tar can handle compressed archives directly with the -z option. Also, the -d option for gzip will delete the original archive file after decompression, which may not be desirable.
• tar cf archive.tgz: This command will create a new archive named archive.tgz from the files and directories given as arguments. However, this command does not use the -z option, so the archive will not be compressed with gzip. Also, this command does not display the contents of the archive, but rather creates it.

 The command foo 1> bar redirects the standard output (stdout) from the command foo to the file bar, overwriting the existing contents of the file. The number 1 before the redirection operator > indicates the file descriptor of the stdout stream, which is 1 by default. The redirection operator > means that the outputof the command is written to the file, replacing any previous data in the file. The file name after the redirection operator is the destination of the output. For example, if the command foo prints “Hello world” to the stdout, and the file bar contains “Goodbye world”, the command foo 1> bar will write “Hello world” to the file bar, erasing “Goodbye world”. The other options are not correct because:

• A. The stdout from the command foo is appended to the file bar: This is not what 1> does, because it overwrites the file, not appends to it. To append the output to the file, the operator >> should be used instead of >.
• C. The command foo receives its stdin from the file bar: This is not what 1> does, because it redirects the output, not the input. To redirect the input from the file, the operator < should be used instead of >.
• D. The command foo receives its stdin from the stdout of the command bar: This is not what 1> does, because it redirects the output to a file, not to another command. To redirect the output to another command, the operator | (pipe) should be used instead of >.
• E. The stderr from the command foo is saved to the file bar: This is not what 1> does, because it redirects the stdout, not the stderr. To redirect the stderr, the file descriptor 2 should be used instead of 1.

The character that, added to the end of a command, runs that command in the background as a child process of the current shell is the ampersand symbol (&). This means that the command will not block the shell and the user can enter other commands while the background command is running. The background command will also not receive any input from the keyboard or the terminal. The shell will print the job number and the process ID of the background command, and the user can use the jobs command to list the status of all background jobs in the current shell session. To bring a background job to the foreground, the user can use the fg command with the job number or the process ID. To terminate a background job, the user can use the kill command with the process ID.

The other characters are not valid or relevant for running a command in the background. The exclamation mark (!) is used to access the command history or to negate a condition. The plus sign (+) is used for arithmetic operations or to append text. The percent sign (%) is used for arithmetic operations or to refer to a job number. The hash sign (#) is used for comments or to specify a hexadecimal number.

References:

• [LPI Exam 101 Detailed Objectives], Topic 103: GNU and Unix Commands, Objective 103.5: Create, monitor and kill processes, Weight: 4, Key Knowledge Areas: Run jobs in the foreground and background.
• How to Run Linux Commands in Background, Topic: Using Ampersand.

The vi command is a text editor that operates in two modes: command mode and insert mode. Command mode is used to enter commands to manipulate the text, such as saving, quitting, copying, pasting, etc. Insert mode is used to enter text into the file. When the vi command is invoked without any additional parameters, it starts in command mode and opens a new empty file. To enter text, the user has to press i to switch to insert mode. To return to command mode, the user has to press Esc. To save and quit, the user has to enter :wq in command mode. The other options are either incorrect or not applicable. The vi command does not load the last file used or the content of the vi buffer by default. It also does not require the user to explicitly create or load a file. It does not exit with an error message unless there is a problem with the terminal or the system. References:

• LPIC-1 Exam 101 Objectives, Topic 103: GNU and Unix Commands, 103.7 Use and edit text files
• LPIC-1 Linux Administrator 101-500 Exam FAQ, LPIC-1 Exam 101 Objectives, GNU and Unix Commands (Total Weight: 25)

The << character is used to create a here document, which is a special type of redirection that reads input from the current source until a line containing only the delimiter (with no trailing blanks) is seen. The delimiter is specified after the << operator, and can be any string. For example, the following command will print everything between the << EOF and EOF lines:

cat << EOF This is a here document It can span multiple lines EOF

The output is:

This is a here document It can span multiple lines

The < character is used for normal input redirection, which reads data from a file or another command. The <| and !< characters are not valid redirection operators in Linux. The &< character is used to duplicate input file descriptors, which is an advanced topic not covered by the Linux Essentials exam. References:

• [LPI Exam 101 Detailed Objectives], Topic 103: GNU and Unix Commands, Objective 103.4: Use streams, pipes and redirects, Weight: 4, Key Knowledge Areas: Redirecting standard input, standard output and standard error.
• [LPI Linux Essentials Certification All-in-One Exam Guide], Chapter 5: Working with Files, Page 167, Using Here Documents.

QUESTIONNO: 16

Which of the following commands will NOT update the modify timestamp on the file /tmp/myfile.txt?

A. file /tmp/myfile.txt

B. echo "Hello" >/tmp/myfile.txt

C. sed -ie "s/1/2/" /tmp/myfile.txt

D. echo -n "Hello" >>/tmp/myfile.txt

E. touch/tmp/myfile.txt

Answer: A

The file command will not update the modify timestamp on the file /tmp/myfile.txt because it only reads the file content and determines its type. It does not write or change anything in the file.

The other commands will update the modify timestamp on the file /tmp/myfile.txt because they either overwrite the file content (B and C), append to the file content (D), or explicitly change the file timestamp (E).

The problem with the command

sed -e “s/a/b/” /tmp/file >/tmp/file

is that it tries to read and write from the same file, which results in overwriting the file before the command can process it. The shell sets up the redirection by opening the file /tmp/file for writing and truncating it to zero length. Then it executes the sed command, which tries to read from the same file, but finds it empty. Therefore, the output is also empty and the file remains empty. A possible solution is to use a temporary file for the output and then rename it to the original file name. For example:

sed -e “s/a/b/” /tmp/file >/tmp/file.tmp && mv /tmp/file.tmp /tmp/file

This way, the original file is not overwritten until the sed command finishes successfully. The other options are either incorrect or not applicable. The file order is correct, the sed command does match something in the file, and the > character is valid for redirection. The | character is used for piping, not redirection. References:

• LPIC-1 Exam 101 Objectives, Topic 103: GNU and Unix Commands, 103.4 Use streams, pipes and redirects
• LPIC-1 Linux Administrator 101-500 Exam FAQ, LPIC-1 Exam 101 Objectives, GNU and Unix Commands (Total Weight: 25)

The tee command reads from standard input and writes to both standard output and one or more files1. Therefore, the command myapp | tee file1.log will send the output of the program myapp to both the terminal and the file file1.log. The other commands will either fail to write to both standard output and file, or write the wrong output. For example, the command cat < myapp | cat > file1.log will try to read the file myapp as input and write it to the file file1.log, but it will not display anything on the terminal. The command myapp 0>&1 | cat > file1.log will redirect the standard input of myapp to its standard output, and then pipe it to the file file1.log, but it will not display anything on the terminal. The command myapp | cat > file1.log will pipe the output of myapp to the file file1.log, but it will not display anything on the terminal. The command tee myapp file1.log will try to read from standard input and write to both the file myapp and the file file1.log, but it will not execute the program myapp. References:

• [LPI Linux Essentials - 1.3 Basic Editing]
• [LPI Linux Essentials - 1.4 I/O Redirection]
• [LPI Linux Essentials - 1.5 Manage Simple Partitions and Filesystems]

The PATH variable defines the directories in which a Bash shell searches for executable commands. The PATH variable is a colon-separated list of directories that the shell scans when a command is entered. For example, if the PATH variable is set to /usr/local/bin:/usr/bin:/bin, then the shell will look for the command in these three directories, in order. If the command is not found in any of these directories, the shell will report an error message. The other options are either invalid or do not perform the desired task. The BASHEXEC, EXECPATH and PATHRC variables are not valid Bash variables. The BASHRC variable is used to specify a file that is executed whenever a new interactive shell is started, but it does not affect the command search path. References:

• LPIC-1 Exam 101 Objectives, Topic 103: GNU and Unix Commands, 103.1 Work on the command line
• LPIC-1 Linux Administrator 101-500 Exam FAQ, LPIC-1 Exam 101 Objectives, GNU and Unix Commands (Total Weight: 25)

The file in the /proc filesystem that lists the parameters passed from the bootloader to the kernel is /proc/cmdline. This file contains a single line of text that shows the command line arguments that were used to boot the kernel. These arguments can include various options, such as the root device, the init process, the console device, and more. The /proc/cmdline file is read-only and cannot be modified at runtime. The parameters in this file are determined by the bootloader configuration, such as GRUB or LILO, and can be changed by editing the corresponding files12.

References: 1: The /proc Filesystem — The Linux Kernel documentation 2: passing bootloader arguments to the kernel - Unix & Linux Stack Exchange

The shutdown command is used to bring the system down in a safe and controlled way. It can take various options and arguments, such as the time of shutdown, the message to broadcast to users, the halt or reboot mode, etc. The option -r instructs the shutdown command to reboot the system after shutting down. The argument now means to shut down immediately. Therefore, shutdown -r now will reboot the system without delay. The telinit command is used to change the run level of the system. It takes a single argument that specifies the new run level. The run level 6 is reserved for rebooting the system. Therefore, telinit 6 will also reboot the system. The other options are either incorrect or irrelevant. shutdown -r “rebooting” will also reboot the system, but with a delay of one minute and a message to the users. telinit 0 will halt the system, not reboot it. shutdown -k now “rebooting” will only send a warning message to the users, but not actually shut down or reboot the system. References: LPI Linux Essentials - 1.101.2, LPI Linux Administrator - 101.3

The USB device filesystem can be found under /proc/bus/usb/1. This is a virtual filesystem that provides information about the USB devices and buses connected to the system12. It contains files and directories that correspond to the USB host controllers, hubs, and devices12. For example, the following output shows the contents of /proc/bus/usb/ on a system with one USB host controller and two USB devices:

The directories 001 and 002 represent the USB buses, and each contain files that represent the USB devices on that bus. The file devices contains a summary of all the USB devices and their configurations. The file drivers contains a list of the USB drivers and the devices they are bound to12.

The /proc/bus/usb/ filesystem is deprecated and should not be used anymore3. It has been replaced by the /sys/bus/usb/ filesystem, which is a sysfs mount that provides more detailed and structured information about the USB devices and buses3 .

References:

1: USB in a NutShell - Chapter 5 - Linux USB 2: Linux USB FAQ 3: Alternative to /proc/bus/usb/devices - Super User : [What is the difference between /dev/usb, /proc/bus/usb and /sys/bus/usb? - Super User]

The command that would disconnect the users and allow you to safely execute maintenance tasks on a disk partition is telinit 112. The telinit command is used to change the runlevel of the system, which is a mode of operation that defines what processes and services are running3. The runlevel 1, also known as single-user mode, is a mode that allows only the root user to log in, and disables all network services and graphical interfaces4. This mode is useful for performing system maintenance and recovery tasks, such as repairing a disk partition5.

The other options in the question are not correct because:

• B. shutdown -r now: This command would reboot the system immediately, without disconnecting the users gracefully or allowing you to do any maintenance tasks.
• C. killall -9 inetd: This command would kill the inetd process, which is a daemon that manages network services. This would not disconnect the users who are already logged in, and it would not stop other processes that might interfere with the maintenance tasks.
• D. /bin/netstop --maint: There is no such command in Linux.
• E. /etc/rc.d/init.d/network stop: This command would stop the network service, which would disconnect the users who are logged in remotely, but not the ones who are logged in locally. It would also not stop other processes that might interfere with the maintenance tasks.

References:

1: How to Change Runlevels (targets) in SystemD - Tecmint 2: How to Boot into Single User Mode in CentOS/RHEL 7 - Tecmint 3: Runlevel - Wikipedia 4: Single-user mode - Wikipedia 5: How to Repair a Corrupted Linux File System - Linux.com : [shutdown(8) - Linux manual page] : [inetd(8) - Linux manual page] : [How to Start/Stop or Enable/Disable firewalld on CentOS 7 - Tecmint]

The command that displays the contents of the Kernel Ring Buffer on the command line is dmesg12. The dmesg command is a Linux utility that displays kernel-related messages retrieved from the kernel ring buffer12. The ring buffer stores information about hardware, device driver initialization, and messages fromkernel modules that take place during system startup12. The dmesg command is invaluable when troubleshooting hardware-related errors, warnings, and for diagnosing device failure2.

The dmesg command can be used with various options to control the output format, filter the messages by facility or level, clear the ring buffer, or follow the new messages in real time123. For example, the following command displays the last 10 messages from the kernel ring buffer:

$ dmesg | tail -10

The following command displays the messages from the kernel ring buffer in a human-readable format with colored output:

$ dmesg -H --color

The following command displays the messages from the kernel ring buffer that have the facility kern and the level emerg:

$ dmesg -f kern -l emerg

The following command clears the ring buffer:

$ dmesg --clear

The following command keeps dmesg running and waiting for new messages:

$ dmesg -w

References:

1: dmesg Linux Command {Syntax, Options and Examples} - phoenixNAP 2: Ubuntu Manpage: dmesg - print or control the kernel ring buffer 3: Display Recent Kernel Messages (console, kernel ring buffer, facilities)

The commands init 1 and telinit 1 both bring a system running SysV init into a state in which it is safe to perform maintenance tasks. This state is also known as single-user mode or runlevel 1, where only the root user can log in and no network services are running. The command shutdown -R 1 now is incorrect, because it reboots the system instead of entering single-user mode. The command shutdown -single now is invalid, because the -single option does not exist for the shutdown command. The command runlevel 1 is also invalid, because runlevel is a command that displays the current and previous runlevels, not a command that changes the runlevel. References:

• 1: SysVinit - ArchWiki
• 2: Linux: How to write a System V init script to start, stop, and restart my own application or service - nixCraft
• 3: sysvinit - Gentoo wiki

 The command dmesg will display messages from the kernel that were output during the normal boot sequence. The dmesg command reads the kernel ring buffer, which is a data structure that stores the most recent messages generated by the kernel. The dmesg command can also be used to display messages from the kernel that were output after the boot sequence, such as hardware events, driver messages, or system errors. The dmesg command has various options to filter, format, or save the output. For example, dmesg -T will display human-readable timestamps for each message, and dmesg -w will display the messages in real time as they occur. References:

• 1: How to view all boot messages in Linux after booting? - Super User
• 2: dmesg(1) - Linux manual page
• 3: Kernel ring buffer - Wikipedia

The first program that is usually started, at boot time, by the Linux kernel when using SysV init is /sbin/init. This program is responsible for reading the /etc/inittab file and executing the appropriate scripts and programs for each runlevel. The other options are not valid programs that are started by the kernel. /lib/init.so is a shared library that is used by some init programs, but not by SysV init. /etc/rc.d/rcinit is a script that is run by init, not by the kernel. /proc/sys/kernel/init is a kernel parameter that can be used to specify a different init program, but the default value is /sbin/init. /boot/init is not a standard location for an init program, and it is unlikely that the kernel would find it there. References:

• 1: SysVinit - ArchWiki
• 2: Linux: How to write a System V init script to start, stop, and restart my own application or service - nixCraft
• 3: sysvinit - Gentoo wiki

The bootloader is a program that is executed by the BIOS after it completes its tasks of initializing the hardware and performing the POST (Power-On Self Test). The bootloader is responsible for loading the kernel and other necessary files into memory and passing control to the kernel. The bootloader can be either installed in the Master Boot Record (MBR) of the disk or in a separate partition. Some examples of bootloaders are GRUB, LILO, and SYSLINUX. References: LPI Linux Essentials - 1.101.1, LPI Linux Administrator - 102.1

The lspci command can display information about the system hardware, such as:

• Device IRQ settings1: The lspci command can show the interrupt request (IRQ) number assigned to each device by using the -v option. The IRQ number indicates how the device communicates with the CPU.
• PCI bus speed2: The lspci command can show the speed of the PCI bus by using the -vv option. The speed is expressed in megahertz (MHz) or gigahertz (GHz) and indicates how fast the data can be transferred between the device and the bus.
• Device vendor identification3: The lspci command can show the name and identification number of the device vendor by using the -n or -nn option. The vendor identification helps to identify the manufacturer and model of the device.

References: 1: https://www.man7.org/linux/man-pages/man8/lspci.8.html  2: https://phoenixnap.com/kb/lspci-command  3: https://en.wikipedia.org/wiki/Lspci

 The BIOS (Basic Input/Output System) is a firmware that is stored in a ROM chip on the motherboard and is responsible for initializing the hardware and loading the bootloader. The BIOS has a setup utility that allows the user to configure various settings, such as the boot device order, the hardware configuration, the system date and time, the security options, etc. The BIOS does not store information about the Linux kernel version, the time zone, or the system’s hostname, as these are part of the operating system and are not relevant for the BIOS. References: LPI Linux Essentials - 1.101.1, LPI Linux Administrator - 102.1

 Run levels are predefined modes of operation in the SysV init system that determine which processes and services are started or stopped. The default run level is the one that the system enters after booting. It is usually specified in the /etc/inittab file with a line like id:5:initdefault:. The run levels 0 and 6 should never be declared as the default run level because they are used to halt and reboot the system, respectively. If they are set as the default, the system will enter an endless loop of shutting down and restarting. The other run levels (1-5) have different meanings depending on the distribution, but they usually correspond to single-user mode, multi-user mode, network mode, graphical mode, etc. References: LPI Linux Essentials - 1.101.2, LPI Linux Administrator - 101.3