RH033 Red Hat Linux Essentials Questions and Answers

The lpc command is used to check the status of printers, enable and disable printers, and change the arrangement of jobs in the print queue.

Answer option D is incorrect. The lpr command sends a job to the queue to be printed.

Answer option A is incorrect. The lpq command views the contents of the print queue.

Answer option B is incorrect. The lprm command removes a job from the print queue.

The evince utility is used to view PDF files on the Linux operating system.

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]

Answer options B and D are incorrect. These commands are used to convert a text to PostScript and send it to a file or the print queue.

What is PostScript?

PostScript is a language developed by Adobe Systems for printing documents on laser printers. It can also be adapted to produce images on other types of devices. It is the standard for desktop publishing. Every PostScript printer contains a built-in interpreter that executes PostScript instructions. Level 1, Level 2, and PostScript 3 are three basic versions of PostScript language.

Answer option A is incorrect. The ps2pdf utility is used to create PDF files.

The /etc/group file contains group information. This file shows which users are members of which groups.

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:

According to the scenario, John wants to change the modified date and time of the file private.txt to a desired date and time. For this, he can use either the touch -t or touch -d command. The difference between these two commands is that the touch -d command is more flexible, while the touch -t command takes the date and time in the format MMDDhhmm.ss.

The scp command copies files between hosts on a network. It uses ssh for data transfer, and uses the same authentication and provides the same security as ssh. Unlike rcp, scp will ask for passwords or passphrases if they are needed for authentication. Any file name may contain a host and user specification to indicate that the file is to be copied to/from that host.

Copies between two remote hosts are permitted.

According to the scenario, the S status message shows that the process id 24224 is in sleeping status.

The ps -aux command reports the status of processes currently running on a Linux computer. It shows the following status messages:

If no path is given, find looks in the current directory and its subdirectories. Using the -i option tells the find command to perform caseinsensitive search for files named snow.html. It will show all files named snow.html, Snow.html,

SNOW.html in the current directory.

Answer option B is incorrect. This command will only search for files named snow.html in the current directory with case-sensitiveness. It will not search for those files named Snow.html, SNOW.html.

Answer option C is incorrect. This is an incorrect command; it will show an error message.

Answer option D is incorrect. This is also an incorrect command, there should be a name after -i in the command.

The ls -al /root command lists all the files and directories, including hidden files in the /root

directory, in long listing format. /root is the root

user's home directory.

What is the ls command?

The ls command is used to list files on a Linux computer. The syntax of the ls command is as follows:

ls [option] [directory name]

Several options are used with the ls command. Following is a list of some important options:

For example, the following command displays all the files (including hidden files) in the /home

directory and the contents in

the subdirectories:

ls -aR /home

Answer option B is incorrect. The ls command without arguments lists the file and directory names

in the current directory.

Answer option C is incorrect. The ls -s /root command shows the size of all files and directories (in blocks, not bytes) that reside in the /root directory.

Answer option D is incorrect. The ls -h /root command shows the size of files and directories in

"human readable format" (i.e. 19M, 3G, etc).

Answer option C is incorrect. The pdf2ps utility is used to convert a PDF file to a PostScript.

You can use the file command to display the file types of all the files in a directory at a time. In order to accomplish the task, you will have to issue the following command:

file *

What is the file command?

The file command is used to analyze the files specified in the argument.

Syntax:

file [] [] ...

By providing the name of a file as an argument, the file command analyzes the file. The file command supports multiple arguments. The asterix (*) metacharacter can also be used with the file 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.

Answer option A 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.

Answer option D is incorrect. The init command is used to switch a Linux computer to different run levels.

The lprm command is used to remove a job from the print queue.

Answer option C is incorrect. The lpq command is used to view the content of the print queue.

Answer option D is incorrect. The lpr command sends a job to the print queue.

Answer option B is incorrect. The lpc command is used to control the operation of a line printer system.

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.

SELinux is an operating system based on Linux which includes Mandatory Access Control. The

SELinux provides Kernel-level security for Red Hat Enterprise Linux.

Answer options C, B, and A are incorrect. These are the features of SELinux.

What are the features of SELinux?

The features of SELinux are as follows:

SELinux provides Kernal-level security.

SELinux implements Mandatory access control (MAC) security in Red Hat Enterprise Linux.

SELinux assigns every file and process on the system a context, identifying its type and purpose.

SELinux enforces a policy that dictates which actions a given type of process may take on a given type of file

SELinux applies to all users, including root.

The nice command is used to change the priority of a process in the kernel's scheduler.

A niceness of -20 is the highest priority and 19 is the lowest priority. The default niceness for processes is inherited from its parent process, usually 0. For example, when specifying a very low priority, the following command can be entered: nice -n 19 cc -c *.c &

The above command runs the cc command in the background at a lower priority than the default priority set by the nice command.

The lprm command is used to remove the print jobs that have been queued for printing. If no arguments are supplied, the current job on the default destination is cancelled. The command syntax for the lprm command is as follows:

lprm [-E] [-U username] [-h server[:port]] [-P destination[/instance]] [-] [job ID(s)]

where,

Since John wants to use the variable VAR1 as an environmental variable, he will use the export command to accomplish the task.

The /etc/profile shell script is the first startup script run when a login shell is started. It runs only for the login shell.

What is a Login shell?

A login shell is a shell that is started by login into the system. The login shells' responsibility is to start the non-login shell

and to make sure that environment variables are set so as to ensure that a user can get all the default parameters needed at start-up.

Login shell will set the PATH environment variable, TERM, the UID and GID of the terminal amongst other things. These are the requirements in order to work proficiently. Additionally, the login-shell will set default variable such as USERNAME,

HISTSIZE, HOSTNAME, HOME, etc.

Answer option A is incorrect. The ~/.bashrc shell script is the first startup script run when a non-login shell is started.

A non-login shell is a shell started by a user or a program issuing the bash command.

Some non-login shells are as follows:

su

graphical terminals

executed scripts

any other bash instances

Answer options D and B are incorrect. The non-login shells first call ~/.bashrc. The ~/.bashrc calls

/etc/bashrc, and then /etc/bashrc

calls /etc/profile.d.

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

The commands to put data from a buffer into the document are p and P. p puts the data below the current line and P puts the data above the current line.

What is the p command?

The p command is used to put (paste) data from a buffer into the document. If data is line oriented

(a line or a paragraph), the p command will open a new line below the current line and place the data on this line. If data is character oriented (a letter, word, or sentence), the p command will place the data after the cursor.

What is the P command?

The P command is used to put data from a buffer into a document. How this command works depends on the nature of the data in the buffer. If the data is line oriented, the P command will open a new a line above the current line and paste the data there. If the data is character oriented, the P command will put the data before the cursor. Answer option D is incorrect. The ps command displays the status of the current processes in Linux. Answer option A is incorrect. The :set command lists a small number of important configuration items in vim.