Pass the LPI LPIC Level 1 101-500 Questions and answers with CertsForce

The mount command is used to attach a filesystem to a directory on the system, which is called a mount point. The mount command requires the device name or the UUID of the filesystem as the first argument, and the mount point as the second argument. Optionally, the mount command can also take some options, such as the filesystem type, the mount options, and the label. The syntax of the mount command is:

mount [options] device mountpoint

In this question, the device name of the CD-ROM is /dev/sr0, and the mount point is /mnt/cdrom. Therefore, the correct command to mount the CD-ROM is:

mount /dev/sr0 /mnt/cdrom

This command will mount the CD-ROM as a read-only filesystem with the type iso9660, which is the standard format for optical discs. The mount command can automatically detect the filesystem type and the mount options, so there is no need to specify them explicitly. However, if you want to specify them, you can use the -t and -o options, respectively. For example, the following command is equivalent to the previous one:

mount -t iso9660 -o ro /dev/sr0 /mnt/cdrom

The other options are not correct because:

A. mount /dev/cdrom /mnt/cdrom: This command may work on some systems, but it is not guaranteed to be correct. The /dev/cdrom is usually a symbolic link to the actual device name of the CD-ROM, which can vary depending on the system. For example, on some systems, the /dev/cdrom may point to /dev/sr0, but on others, it may point to /dev/scd0 or /dev/hdc. Therefore, it is better to use the actual device name of the CD-ROM, which can be found by using the lsblk or the dmesg command.

C. mount -t cdrom /dev/sr0 /mnt/cdrom: This command is not valid because cdrom is not a valid filesystem type. The filesystem type for optical discs is iso9660, not cdrom. The mount command will fail with an error message saying:

mount: unknown filesystem type ‘cdrom’

D. mount -l cdrom /dev/sr0 /mnt/cdrom: This command is not valid because -l is not a valid option for the mount command. The -l option is used to list all the mounted filesystems, not to mount a filesystem. The mount command will fail with an error message saying:

mount: can’t find /dev/sr0 in /etc/fstab

E. mount -f /dev/sr0/mnt/cdrom: This command is not valid because it is missing a space between the device name and the mount point. The mount command requires two separate arguments for the device name and the mount point, separated by a space. Also, the -f option is used to fake the mount operation, not to perform the actual mount. The mount command will fail with an error message saying:

mount: /dev/sr0/mnt/cdrom: mount point does not exist.

The dpkg command is used to manage Debian packages on Linux systems. The -r option removes a package but leaves its configuration files in case the package is re-installed. The -P option purges a package and removes its configuration files as well. The -s option shows the status of a package and the -L option lists the files installed by a package. References:

LPI Linux Essentials, Chapter 6: Managing Software, Section 6.2: Debian Package Management

LPI Linux Administrator, Exam 101: System Architecture, Topic 102: Linux Installation and Package Management, Objective 102.5: Manage shared libraries

LPI Linux Engineer, Exam 201: Linux Kernel, Topic 201: System Architecture, Objective 201.1: Kernel Components and Compilation

The :e command in vi is used to edit a file. If the file name is not specified, it will edit the current file. If the file has been changed by another process, the :e command will reload the file with the new content, discarding any unsaved changes made in vi. Therefore, the :e command can be used to reopen the file for editing with the new content without exiting vi. The other options are either invalid or do not perform the desired task. The :r command is used to read the content of another file or command and insert it into the current file. The :n command is used to edit the next file in the argument list, if any. The :w command is used to write the current file to disk, optionally with a new name. 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 <, > and %> are valid stream redirection operators within Bash. The < operator redirects the standard input of a command from a file or another command. For example, sort < names.txt will sort the lines of the file names.txt and print them to the standard output. The > operator redirects the standard output of a command to a file or another command, overwriting the file if it exists. For example, echo "Hello World" > greeting.txt will write the string “Hello World” to the file greeting.txt. The %> operator redirects the standard error of a command to a file or another command, overwriting the file if it exists. For example, ls foo %> errors.log will list the contents of the directory foo and write any error messages to the file errors.log. The other options are either invalid or do not perform the desired task. The <<< operator is not a valid Bash operator, but it is used in some other shells like Zsh to redirect a string literal as the standard input of a command. The >>> operator is not a valid Bash operator, but it is used in some programming languages like Python to denote a bitwise right shift operation. 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 -v option for the egrep command activates the invert matching mode, which means that it only outputs the lines that do not match the given pattern or regular expression. This is useful for filtering out unwanted lines or finding exceptions in a file. For example, the following command will output all the lines in the file my_text that do not contain the word “Linux”:

egrep -v Linux my_text

The -v option can be combined with other options to modify the output format or behavior of the egrep command. For example, the -c option will count the number of non-matching lines instead of printing them, and the -i option will ignore the case of the pattern while matching. 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 egrep to search for extended regular expressions in text output.

[Linux egrep Command with Examples], Topic: Invert Matching with egrep.

The maximum niceness value that a regular user can assign to a process with the nice command when executing a new process is 19. The niceness value is a user-space value that controls the priority of a process. The lower the niceness value, the higher the priority, and vice versa. The niceness value range is -20 to +19, where -20 is the highest priority and +19 is the lowest priority. The default niceness value is 0. The nice command can be used to run a new process with a modified niceness value. The syntax is: nice -n value command, where value is the niceness value and command is the process to run. For example, nice -n 10 sleep 60 will run the sleep command with a niceness value of 10 for 60 seconds. However, regular users can only increase the niceness value of their processes, not decrease it. This means that they can only lower the priority of their processes, not raise it. The minimum niceness value that a regular user can assign is 0, and the maximum is 19. Only the root user can assign a negative niceness value, which means raising the priority of a process. For example, nice -n -10 sleep 60 will run the sleep command with a niceness value of -10 for 60 seconds, but only if the user is root. The other options are not correct because:

A. 9 is not the maximum niceness value that a regular user can assign, but a valid niceness value within the range.

C. 49 is not a valid niceness value, as it exceeds the maximum of 19.

D. 99 is not a valid niceness value, as it exceeds the maximum of 19.

The export command is a Bash built-in command that exports environment variables and functions for use in other shell sessions1. Environment variables are named values that affect the behavior of applications and processes2. For example, the PATH variable stores a list of directories where executable programs are located, and the LANG variable sets the language and locale of the system2. By using the export command, you can make these variables available to any child process spawned by the current shell1. For example, if you want to set the EDITOR variable to vim for all subshells, you can run:

export EDITOR=vim

The export command can also be used to export functions, which are blocks of code that can be reused by invoking their name3. For example, if you want to create and export a function that prints “Hello world”, you can run:

hello () { echo “Hello world”; } export -f hello

Then, you can call the hello function in any subshell or script that inherits the environment from the current shell.

The other options are not related to the export command. Option A refers to the mount command, which attaches a filesystem to a directory4. Option B refers to the command substitution feature, which runs a command in a subshell and replaces it with its output5. Option C refers to the history command, which displays the command history of the current shell. Option E refers to the exportfs command, which maintains the table of exported NFS shares.

 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.

The command that will reduce all consecutive spaces down to a single space is tr -s ’ ’ < a.txt > b.txt. This command uses the following options and syntax:

-s: Squeezes repeated characters listed in the first set with single occurrence.

’ ': Specifies a space character as the first set.

< a.txt: Redirects the input from a file named a.txt.

b.txt: Redirects the output to a file named b.txt.

The output of this command will be a new file called b.txt that contains the same text as a.txt, except that any sequence of multiple spaces will be replaced by a single space. For example, if the file a.txt contains the following text:

This is a text file with multiple spaces.

The file b.txt will contain the following text:

This is a text file with multiple spaces.

The other commands are incorrect for the following reasons:

A. tr ‘\s’ ’ ’ < a.txt > b.txt: This command will replace every whitespace character (\s) with a space character, which will not reduce the number of spaces, but rather convert tabs and newlines into spaces.

B. tr -c ’ ’ < a.txt > b.txt: This command will complement the first set, meaning that it will apply the operation to all characters that are not spaces. This will not affect the spaces at all, but rather squeeze all other characters.

C. tr -d ’ ’ < a.txt > b.txt: This command will delete all spaces from the input, which will not reduce them to a single space, but rather remove them completely.

D. tr -r ’ ’ ‘\n’ < a.txt > b.txt: This command will replace all spaces with newlines, which will not reduce the spaces, but rather create a new line for each word.

 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 output of 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.