Practice Free RH033 Red Hat Linux Essentials Exam Questions Answers With Explanation

The second column in the listing shows the number of hard links created for the file.

The Ctrl-r key-combination is used to redo a change undone by a u command in vim. You can go back in time with the undo command. You can then go forward again with the redo command. If you make a new change after the undo command, the redo will not be possible anymore.

Answer options B and D are incorrect. The Ctrl-w, s and Ctrl-w, v key-combinations are used to view a file in two windows in a single vim screen. Ctrl-w, s splits the screen horizontally and Ctrl-w, v splits the screen vertically.

Answer option A is incorrect. The Ctrl-w key-combination with an arrow key is used to jump from one window to another. This will move you to the next window in whichever direction the arrow would normally move your cursor.

The pwd command-line utility is used to display the current working directory.

What is the pwd command?

The pwd command prints the complete pathname of the current working directory to the standard output.

pwd [ -L | -P]

The options are described as follows:

OptionDescription

-LDisplays the logical current working directory.

-PDisplays the physical current working directory.

If no options are specified, the -L option is assumed.

Answer option A is incorrect. The ls command lists the contents of the current directory or the specified directory.

Answer option D is incorrect. The cd command with no argument is used to move to your home directory.

Answer option C is incorrect. The mv command is used to move and/or rename files and directories.

The less command is most useful for viewing large files. The less command displays the output of a file one page at a time. Viewing large files through cat may take more time to scroll pages, so it is better to use the less command to see the content of large files.

Answer option B is incorrect. The cat command is also used to view the content of a file, but it is most useful for viewing short files.

Answer option A is incorrect. The cp command is used to copy files and directories from one location to another.

Answer option D is incorrect. The touch command is not used to view the content of a file. It is used to create empty files or to update file timestamps.

This command will prompt you to remove Joe's tmp files that are 3 days older. When the -ok option is used with the find command it causes find to execute the rm command once for each /tmp file that is 3 days older. {} can be used as a filename placeholder.

The -ok option with the find command is used to execute a command once for each file that matches the given criteria. This is commonly used in situations such as removing files or renaming files to have a certain extension. The -ok option causes find to ask for each file before removing it.

What is the find command?

The find command is a versatile method for locating files on a file system. The syntax for this command is as follows:

find -

Some of the important criteria are described in the table below:

What are some numeric criteria that the find command uses?

The find command can search your system for files that comply with certain numeric criteria. For

example, -ctime, -atime, -

cmin, -amin, etc. The -ctime and -atime are measured in days and the -cmin and -amin are measures in minutes.

For example:

find /tmp -ctime +10

This command searches for files that are more than 10 days older.

find /tmp -cmin +10

This command searches for files that are more than 10 minutes older.

What is the purpose of using \; at the end of the find command?

The purpose of using \; at the end of the find command is that when find is used with -exec and –ok the find command uses ; as the delimiting character. Unfortunately ; is also a delimiting character for the bash shell so we must prevent bash from interpreting it. When a character is preceded with a backslash (\), bash instructs it literally, so typing \; at the bash command prompt will send ; to find command after bash has done its interpretation.

Answer option A is incorrect. This command will prompt you to remove Joe's tmp files that are 3 minutes older.

Answer options D and B are incorrect. These are the incorrect command syntaxes.

You will use the yum install firefox command to install the package named firefox in the Linux system. This command will search the configured repositories for the package named firefox, and if found, will install the latest version, pulling in dependencies if needed.

Answer options B and D are incorrect. The -ivh and i options are not used with the yum command.

Answer option A is incorrect. The yum update firefox command is used to update a package in the Linux system. It is not used to install a package in Linux. If run without any specified package, the update option will update every currently installed package. If one or more packages are specified, yum will only update the listed packages. While updating packages, yum will ensure that all dependencies are satisfied.

The LPRM command is used to remove a file from a print queue.

Answer option D is incorrect. The LPQ command reports the status of a print queue.

Answer option A is incorrect. The LPR command is used to submit a file for printing.

Answer option B is incorrect. There is no command such as LPQDEL in Linux.

The nl install.log and sed = install.log commands can be used to assign a line number to every line of the install.log file.

Answer options C and D are incorrect. The wc -c install.log and wc -m install.log commands will print the number of bytes and the number of characters, respectively.

You can view all running processes with the help of the ps -aux command. Hence, any of the ps –aux commands (i.e., ps -aux | grep cc, ps -aux

| more, or ps -aux) can be used to check whether the cc process is running on the computer.

Answer option B is incorrect. The tail command is used to display the last few lines of a text file or piped data. It has a special command line option -f (follow) that allows a file to be monitored. Instead of displaying the last few lines and exiting, tail displays the lines and then monitors the file. As new lines are added to the file by another process, tail updates the display. This is particularly useful for monitoring log files. The following command will display the last 10 lines of messages and append new lines to the display as new lines are added to messages: tail -f /var/adm/messages

The Interface configuration files are read by system-config-network, ifup, ifdown, and other tools that bring network interfaces up and down.

Answer option B is incorrect. The system-config-services tool is used to manage services in Linux.

The jobs command lists the jobs that are running in the background and in the foreground. If the prompt is returned with no information, no jobs are present.

Syntax:

jobs [-p | -l] [-n] [-p] [-x] [job id]

Some important options used with jobs command are as follows:

Answer option A is incorrect. The top command is used to produce a frequently-updated list of processes. By default, the processes are ordered by percentage of CPU usage, with only the "top" CPU consumers shown. This command shows how much processing power and memory are being used, as well as other information about the running processes. The following figure demonstrates the output of the top command:

Answer option B is incorrect. The bg command can be used to resume in the background when a process is suspended.

Answer option C is incorrect. There is no such command as job.

Kernel files do not change regularly and therefore are contained in the /boot directory, not in the

/var directory.

What is the /var directory?

According to the Filesystem Hierarchy Standard, the /var directory contains regularly-changing system files. This comprises spool directories and files, and administrative and logging data.

Answer option A is incorrect. System log files are stored in the /var directory.

Answer options D and C are incorrect. Print spool files and email-spools are variable data files and therefore are contained in the /var directory.

This command will search for files with a size of over 50 megabytes. The -size option tells find to search files according to the size of files, and

+50M will tell the find command to search files over 50 megabytes.

Answer option C is incorrect. This command will search for files with a size of exactly 50 megabytes.

Answer option B is incorrect. This command will search for files with a size of less than 50 megabytes.

Answer option D is incorrect. - must be prefixed with size, otherwise shell will not recognize this command, and display an error message.

The ps2pdf utility is used to convert PostScript to a PDF file.

What is a ps2pdf command?

The ps2pdf command creates PDF files. It is used to convert a PostScript file to a PDF file.

There are a number of versions of this program, some are as follows:

Answer option D is incorrect. The enscript utility converts a text to a PostScript format and sends it to a file or the print queue.

Answer option B is incorrect. The evince utility is used to view a PDF file, not to create a PDF file.

What is the evince command?

The evince command is a document viewer capable of displaying multiple and single page document formats such as PDF and Postscript.

Syntax: evince [Options] [Filename]

This command will execute a program named My_program and whatever errors are generated while executing that program will all be added to a file named file2 rather than being displayed on the screen.

What is redirection of STDIN, STDOUT, STDERR in Linux?

Redirection means diverting data from their normal destination to another. Whenever a program is executed on terminal some output is displayed at the shell prompt. In case a user does not want that output to appear in the shell window, the user can redirect it elsewhere. The user can redirect the output into a file, printer, etc.

Not only the output of programs is redirected, but also input of a program and error messages are redirected to a file.

Common Redirection operators are as follows:

Answer option D is incorrect. This command will direct the standard output of My_program to file2.

Answer option A is incorrect. This command will append the standard output of My_program to file2.

Answer option C is incorrect. This command cannot be applied in this scenario.

Ctrl-w key-combination with an arrow key is used to jump from one window to another. This will move you to the next window in whichever direction the arrow would normally move your cursor. Instead of the arrow keys, you can also use

vi's traditional h, j, k and l keys for the same effect.

Answer options B and A are incorrect. Ctrl-w, s and Ctrl-w, v key-combinations are used to view a file in two windows in a single vim screen.

Ctrl-w, s splits the screen horizontally and Ctrl-w, v splits the screen vertically.

Answer option D is incorrect. Ctrl-w, q is used to quit from your current window.

The env command is used to list the environment variables that are set on a Linux computer.

The programs that run on a Linux computer are known as processes. When a user starts a program, a new process is created. This process runs within what is called an environment. A user can set parameters in this environment so that the running program can find the desired values. The following syntax is used to set a parameter to a variable:

VARIABLE=value

This would set a parameter by the name VARIABLE with the value that you provide. Some of the commonly used environment variables are HOME, PATH, PS1, etc.

Answer option B is incorrect. The rm command is used to delete files from a directory on a Linux computer.

Answer option C is incorrect. The ls command is used to list files on a Linux computer.

Answer option D is incorrect. The echo $shell command will provide the name of the current shell that a user is using.

In order to accomplish the task, you will have to kill the process and rerun it by using the nice command to lower the priority of the process.

You will have to run the following command: kill : nice -n 19

The nice command is used to run a process with the desired priority level. The priority level varies from 1 to 19. Level 1 is for the highest priority and level 19 is for the lowest. By default, every process runs with the priority level 10.

Answer option C is incorrect. The fg command is used to run a process in the foreground.

Answer option D is incorrect. The bg command is used to run a process in the background.

Answer option A is incorrect. The -n 1 switch will provide the process the top priority.

You will use find -name foobar.png command to do case-senstive search for files named foobar.png.

What is the find command?

The find command can perform a search based on a variety of search limitations. It searches through one or more directory tree(s) of a filesystem, locating files based on some user-specified criteria. By default, find returns all files in the current working directory. Further, find allows a user to specify an action to be taken on each matched file.

Thus, it is an extremely powerful command for applying actions to many files.

The find command can be used with a wild card (*), but it works best when we know the name of the file or directory we are looking for.

The find command can search your system for files that comply with certain numeric criteria, such as the size of the file (-size), the number of links to the file (-links), the date of the last change to the files data (-mtime), or the date of the last time the file was read (-atime). All these criteria accept a numeric value. When a numeric value is provided to find, it looks for an exact match, more than the number, or less than the number.

Answer option B is incorrect. The find -iname foobar.png command will do case-insensitive search for files named foobar.png.

Answer option C is incorrect. The grep-name foobar.png is an invalid command.

What is the grep command?

The grep command is used to search for a specific pattern of text in a file. It helps administrators in searching large amounts of text for a certain error message or name.

Answer option A is incorrect. The locate -name foobar.png is an invalid command.

What is the locate command?

The locate command is used to search for matching files in a database that is usually updated daily by a cron job. On the forthcoming Linux operating systems, this command is usually replaced by the slocate command, which stores permissions as well as paths and thus prevents users from prying into directories. One more advantage of the locate command is that it matches against any part of a pathname, not just the file itself.

The /etc/X11/xdm/xdm-config file is the default configuration file of XDM. The X Window Display

Manager (XDM) is the default display manager for the X Window System. XDM is distributed as part of XFree86 and is configured by a series of files located in /etc/X11/XDM. Some of the important files of XDM are given below in the list:

Xaccess: It is used to control inbound requests from remote hosts.

Xresources: This file holds configuration information for XDM resources and the graphical login screen. It can be edited to modify the appearance of the XDM login screen. Xservers: This file is used to associate the X display names with either the local X server software or a foreign display such as an X terminal.

Xsession: This file contains the script XDM launches after a successful login.

Xsetup_0: This file defines how XDM will open. It is a script started before the graphical login screen.

It often includes commands to set colors, display graphics, or run other programs. This script is executed as root.

XDM-config: This file is used to configure XDM configuration resources.

Answer option B is incorrect. $HOME/.Xauthority is the user authorization file where XDM stores keys for clients to read.

Answer option D is incorrect. The /usr/bin/xterm file is the default session program of XDM.

Answer option C is incorrect. It is not a valid XDM configuration file.

aspell is a utility that can function as an ispell -a replacement, as an independent spell checker, as a test utility to test out Aspell features, and as a utility for managing dictionaries.

Syntax:

aspell [options]

Some important options used with aspell are as follows:

The following options may be used with the aspell command to control which dictionaries to use and how they behave:

Answer option A is incorrect. The tee command is used to split the output of a program so that it can be seen on the display and also be saved in a file. It can also be used to capture intermediate output before the data is altered by another command or program. The tee command reads standard input, then writes its content to standard output, and simultaneously copies it into the specified file(s) or variables.

The syntax of the tee command is as follows: tee [-a] [-i] [File] where, the -a option appends the output to the end of File instead of writing over it and the -i option is used to ignore interrupts.

Answer option B is incorrect. The concatenate (cat) command is used to display or print the contents of a file.

Syntax:

cat filename

For example, the following command will display the contents of the /var/log/dmesg file:

cat /var/log/dmesg

Note: The more command is used in conjunction with the cat command to prevent scrolling of the screen while displaying the contents of a file.

Answer option D is incorrect. There is no such utility as dict in Linux.

This command looks for files on the system whose data has been changed exactly five days ago.

The du command is used to summarize disk usage. The du command displays the number of blocks used for files. If the File parameter specified is actually a directory, the disk usage of all files within the directory are summarized. If no

File parameter is provided, the du command uses the files in the current directory.

Answer option C is incorrect. The df command reports information about space on file systems.

Answer option B is incorrect. The fsck command checks file system consistency and interactively repairs the file system.

Answer option D is incorrect. The dfsck command checks and repairs two file systems simultaneously on different drives.

If there is no free space on the hard disk drive, users will not be able to write on it. To prevent this issue from happening again, you should track the amount of free space on the hard disk. By doing so, you can take necessary actions before the actual problem arises.

Answer option B is incorrect. Even if users save their important files, the hard disk drive will still become full sooner or later.

Answer option A is incorrect. Dedicating a hard disk drive for users to save their files will not prevent the drive from becoming full.

Answer option D is incorrect. The shortage of RAM is not the issue in this scenario.

The yum remove packagename and yum erase packagename commands are used to remove a specified package from a Linux system. If any packages depend on this package, yum will prompt about this and give the option to remove those packages too.

Answer options A and C are incorrect. These commands are incorrect. The -r and -rm options are not used with the yum command to remove a package from a Linux system.

This is the correct syntax for granting ownership of foofile to John.

What is the chown command?

The chown command is used to change the ownership of a file. Only root can change the ownership of a file. The chown command can be used with the -R option to recursively change the ownership of an entire directory tree.

Syntax:

chown [-R] newowner filename

Answer option B is incorrect. The chmod command is used to change access mode for files and directories.

Answer option D is incorrect. The syntax of this command is not correct. With chown, first write the name of the user whom you want to give ownership, then write the filename of the file whose ownership you want to change.

Answer option C is incorrect. The chgrp command is used to change Group-ownership not file ownership.

In Linux, the directories are simply special files that have an inode and a data section.

The contents of the data section are a list of the directory's contents. In order to enter a directory or list its contents, a user must have the Read permission on the directory. The Write permission is required to modify that list.

The following directories cannot be separated from the root filesystem:

/lib

/dev

/etc

/sbin

/bin

Answer option D is incorrect. /var can be separated from the root filesystem. Such filesystems are known as optional filesystems. Some of the optional filesystems are as follows:

/var

/usr

/opt

/home

Set user ID is the Linux access permission flag bit that allows users to run an executable file as the permissions of the executable's owner. When the Set user ID (SUID) bit is set and a user executes the file, the user will have the same rights as the owner.

If the Set user ID bit is set and the owner has the execute permission, the 'x' in the owner permissions is replaced by 's'. If the Set user ID bit is set and the owner has no execute permission, the 'x' is replaced by 'S'.

For example:

-rwsrw----The owner has the execute permission and the SUID bit is set.

-rwSr----- The SUID bit is set, but the owner has no execute permission.

The $! environmental variable represents the PID value of the last child process.

Answer option D is incorrect. The $$ environmental variable represents the PID of the running shell.

Answer option A is incorrect. The $? environmental variable results in the value zero if the last command was executed successfully, otherwise it displays the value one.

Answer option C is incorrect. It is an invalid Linux standard environmental variable.

The bg utility resumes suspended jobs from the current environment by running them as background jobs if job control is enabled. If the job specified by job_id is already a running background job, the bg utility will have no effect and shall exit successfully. Using bg to place a job into the background will cause its process ID to become "known in the current shell execution environment", as if it had been started as an asynchronous list.

Answer option D is incorrect. The fg utility continues a stopped job by running it in the foreground, some shells are not able to run this command.

Syntax:

fg [%job] Where %job specifies the job that a user wants to run in the foreground.

Answer option A is incorrect. The jobs command lists the jobs that are running in the background and in the foreground. If the prompt is returned with no information, no jobs are present.

Syntax: jobs [-p | -l] [-n] [-p] [-x] [job id]

Some important options used with jobs command are as follows:

Answer option C is incorrect. The top command is used to produce a frequently-updated list of processes. By default, the processes are ordered by percentage of CPU usage, with only the "top" CPU consumers shown. This command shows how much processing power and memory are being used, as well as other information about the running processes. The following figure demonstrates the output of the top command:

Using the -f option causes tail to continue to display the file in real time, showing added lines to the end of the file as they occur.

What is the tail -f command?

The tail command is used to display the last few lines of a text file or piped data. It has a special command line option –f (follow) that allows a file to be monitored. Instead of displaying the last few lines and exiting, tail displays the lines and then monitors the file. As new lines are added to the file by another process, tail updates the display.

This is particularly useful for monitoring log files. The following command will display the last 10 lines of messages and append new lines to the display as new lines are added to messages: tail -f /var/adm/messages

Answer option C is incorrect. The cat command simply shows the content of the file when it was last opened, cat does not continue to show updates of the file.

Answer option D is incorrect. The tail -n 3 /var/adm/messages command is used to show most recent entries in log file but it will not continue to show updates of the log file.

Answer option B is incorrect. The tail command will show the last few lines of the log file, but it will not continue to show updates of the log file.

The head -n 5 /etc/passwd command will show the first 5 lines of the file /etc/passwd.

According to the question, the permission set requires setting SID with the owner and the group.

Moreover, the Read, Write, and Execute permissions on the script file are required for the owner, Read and Execute permissions for the group, and Read permission for others.

The chmod command is used to change the permissions. The last three digits, i.e., 754 will provide the required permissions to the owner, group, and others. The digit 7 will provide the Read, Write, and Execute permissions to the owner.

The digit 5 will provide the Read and

Execute permissions to the group. The digit 4 will provide the Read permission to others.

According to the question, you have to set SID for the owner and users. For the owner (SUID), you will have to add 4 as a prefix to the permission number. For the group (SGID), you will have to add 2 as a prefix to it. For setting both the

SIDs (SUID and SGID), you will have to add 6 as a prefix to the permission set. Hence, in order to accomplish the task, you will have to run the following command:

chmod 6754

This will set the SID for the owner and group on the permission set of the lf.cgi script file. When SID is set, the Execute permission symbol x is replaced with s.

The 3l command in vi will move the cursor 3 characters to the right when you are in command mode of vi editor. You can go into command mode by pressing the key.

What is the vi editor?

The vi editor is an interactive, cryptic, and screen-based text editor used to create and edit a file. It operates in either

Input mode or Command mode. In Input mode, the vi editor accepts a keystroke as text and displays it on the screen, whereas in Command mode, it interprets keystrokes as commands. As the vi editor is case sensitive, it interprets the same character or characters as different commands, depending upon whether the user enters a lowercase or uppercase character. When a user starts a new session with vi, he must put the editor in Input mode by pressing the "I" key. If he is not able to see the entered text on the vi editor's screen, it means that he has not put the editor in

Insert mode. The user must change the editor to Input mode before entering any text so that he can see the text he has entered.

Answer option D is incorrect. The 3h command will move the cursor 3 characters to the left.

Answer option B is incorrect. The 3w command will move the cursor forward by 3 words.

Answer option A is incorrect. The 3b command will move the cursor backward by 3 words.

The zip -r foobar.zip filesdir command is used to create a file named foobar.zip and put it into the directory named filesdir. foobar.zip represents the file you are creating and filesdir represents the directory you want to put in the new zip file. The -r option specifies that you want to include all files contained in the filesdir directory recursively.

Answer option A is incorrect. The unzip foobar.zip command is used to extract the contents of a zip file to the filesdir directory.

Answer option D is incorrect. The gunzip foobar.zip command is used to expand the compressed file.

Answer option C is incorrect. The tar -tvf foobar.tar command is used to list the contents of a tar file.

To compare the contents of two files the diff command is used in the Red Hat operating system.

pgrep looks through the currently running processes and lists the process IDs that match the selection criteria to stdout. All the criteria have to match. pkill is a tool that looks up or signals processes based on name and other attributes. Pkill will send the specified signal (by default SIGTERM) to each process instead of listing them on stdout.

Answer option A is incorrect. The top command is used to produce a frequently-updated list of processes. By default, the processes are ordered by percentage of CPU usage, with only the "top" CPU consumers shown. This command shows how much processing power and memory are being used, as well as other information about the running processes. The following figure demonstrates the output of the top command:

Answer option C is incorrect. The sort command is used to print the lines of its input or concatenation of all files listed in its argument list in sorted order. Sorting is done based on one or more sort keys extracted from each line of input. By default, the entire input is taken as the sort key. The blank space is taken used as the default field separator in the output of the sort command.

The -r flag, however, reverses the sort order. For example, the ls -s | sort -nr command will sort the directories of the root directory in reverse order of size.

The chmod command is used to change file access permissions in Linux.

Syntax: chmod [option] [mode]

Option: The following is a list of some important options that can be provided with the command:

Mode: Mode is written in the following format:

[ugoa] [+-=] [rwxXstugo]

The combination of ugoa specifies the users for whom the file access permissions will be changed. In

ugoa, u is for the user who owns the file,

g is for other users in the file group, o is for other users not in the file group, and a is for all users.

The operator + adds the specified permissions to the existing permissions of each file. The - operator

removes, and the = character specifies

that the specified permissions are the only permissions for that file.

The combination of rwxXstugo is permission type. In rwxXstugo, r is for read, w is for write, x is for

execute, X is to execute only if the file is a

directory or already has execute permission for some user, s is to set user or group ID on execution, t

is to save program text on swap device,

u are the permissions that the user who owns the file currently has for it, g are the permissions that

other users in the file group have for the

file, and o are the permissions that other users not in the file group have for the file.

Answer option A is incorrect. The chown command is used to change the user or group ownership of

the files specified with the command.

Answer option D is incorrect. The chgrp command is used to change only the group ownership of the

files specified with the command.

What is the chgrp command?

The chgrp (from change group) command is used by unprivileged users to change the group

associated with a file. Unlike the chown command, chgrp allows regular users to change groups, but only to one of which they are

a member. The

general syntax of the chgrp command is as follows:

chgrp group target1 [target2 ..]

The group parameter indicates the new group with which the targets should be associated.

The target1 parameter indicates the files or directories for which the change should be made.

The target2 parameter indicates the optional additional files or directories for which the change

should be made.

For example:

The above command changes the group associated with ttt to 'system', provided the executing user is a member of that group.

Answer option C is incorrect. There is no such command as chperm in Linux.

The fdisk command is a menu-based command available with Linux for hard disk configuration. This command can perform the following tasks:

Delete a partition on a hard disk.

Create a partition on a hard disk.

Change the partition type.

Display the partition table.

Note: The sfdisk command-line utility is an alternative to the fdisk command.

Answer option C is incorrect. In Linux, the mount command is used to mount and display disks, partitions, and file systems. Mounting refers to the process in which the operating system prepares the media to be read.

Anwer option D is incorrect. The File System Check (fsck) command is used to scan all disks and partitions, and it repairs them if required. The

fsck command should be run only on an unmounted file system.

Note: The function of the fsck command is similar to that of the Window's scandisk utility.

Answer option B is incorrect. There is no such command as crpar in Linux.