RH033 Red Hat Linux Essentials Questions and Answers

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

The cp command in option A will copy file3.txt to the destination /home/john/backup. The source and destination paths have been used correctly.

In option D ~ refers to home directory so it is also the correct destination path.

In option B appending / to the destination just tells the cp command explicitly that you are referring to a directory, not a file.

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.

In order to accomplish the task, you should create a recurring CRON job to delete the temporary files on the server.

According to the scenario, you will use newgrp command to accomplish the task. The newgrp command is used to temporarily change the primary group of a user into another group of which that user is a member. In this step, a new shell will be created, and when that user will exit from the shell, his previous group will be reinstated. If no group is specified, the GID is changed to the login GID.

Answer option C is incorrect. John will not use the chgrp command to accomplish his task. 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 D is incorrect. John will not use the chown command to accomplish his task. The chown command is used to change the user and/or group ownership of each given file as specified by the first non-option argument as follows: if only a user name (or numeric user ID) is given, that user is made the owner of each given file, and the file's group is not changed.

If the user name is followed by a colon and a group name (or numeric group ID), with no spaces between them, the group ownership of the files is changed as well.

The syntax of the chown command is as follows: chown [-R [ -H | -L | -P ]] [ -h ] owner[:group] file ...

Answer option A is incorrect.

The chmod command is used to change the access mode of a file. The syntax of the command is: chmod who=permissions filename

Here, "who" refers to the owner of the file, group members, or other users, and permissions refers to "rwx".

For example, chmod 755 File.txt will give all access permissions to the owner and the read and execute permissions to the group members and other users.

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.

Note: The swap file system cannot be mounted using the mount command.

Answer option D is incorrect. In Linux, the UMOUNT command is used to unmount a file system from its mount point.

Answer options A and B are incorrect. There are no such commands as attach and detach in Linux.

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 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.

The lpc command can be used to rearrange jobs awaiting printing, as well as to disable/enable a

printer or queue and find the status of printers.

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

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

Answer option C is incorrect. The lprm removes a job from the queue.

creates a command prompt at bottom-left of screen. w will save the file and q will quit from the file. When :wq is used in combination and then the Enter key is pressed, this will save the file and exit it.

Answer option D is incorrect. : enters EX mode. EX mode will open a prompt on the last line of the terminal, and will accept certain keys for commands.

Answer option A is incorrect. :w only saves a file on the disk. To quit from the file after saving its contents, use q after :w.

Answer option C is incorrect. This key is used to quit from the file without saving its contents.

A file's inode number can easily be found by using the ls command with the -i option.

What is an inode?

An inode is a data structure in Unix file systems, which holds key information about a file. A file is uniquely identified by its

inode number. An inode contains the following information about a file:

Owner's user identification number

Owner's group identification number

Device on which the inode resides

Locking information of the file

Mode and type of file

Number of links to the file

Size of the file

Access and modification time of the file

Modification time of the inode

Addresses of the blocks of the file on the disk

Answer option D is incorrect. ls without arguments lists the names of files and directories in the current directory.

Answer option A is incorrect. The cat command only displays the contents of a file, not the file's inode number.

Answer option C is incorrect. This command displays the long listing of files and directories. It will not display the inode number of a file.

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

The Ctrl+Alt+Backspace key combination is used to terminate the X session.

Answer option A is incorrect. The Ctrl+Alt+F7 key combination is used to switch from a virtual console back to the X terminal.

Answer option C is incorrect. The Ctrl+Alt+Fn key combination is used to switch from graphical mode to the nth (n varies from 1-6) virtual console running in text mode.

Answer option D is incorrect. Ctrl+Alt+A is not a valid key combination to terminate the X session.

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.

All these information are stored in the /etc/passwd file.

What is the /etc/passwd file?

In Linux operating systems, the /etc/passwd file lists information about each of the users that may login to the system. The file is so named because originally it also contained the data used to verify passwords. However, on

modern Unix systems, the security-sensitive password information is instead often stored in a different file using shadow passwords.

The /etc/passwd file typically has world-readable permissions, though it may only be edited by the

superuser or by using a few special purpose commands.

The first field is the user name. Each record in the file must have a unique user name field.

The second field stores information used to confirm a user's password; however, in most modern uses, this field is usually set to "x" (or some other indicator) with the actual password information being stored in a separate shadow password file.

The third field is the user identifier, the number that the operating system uses for internal purposes. It does not have to be unique.

The fourth field is the group identifier. This number identifies the primary group of the user; all files that are created by this user will initially belong to this group.

Reserved gecos ID (Typically, this is a set of comma-separated values including the user's full name

and contact details).

The sixth field is the path to the user's home directory.

The seventh field is the shell program that is started every time the user logs into the system.

Answer option C is incorrect. The shadow password is stored in the /etc/shadow file.

What is /etc/shadow file?

The /etc/shadow file stores the account information in the following format:

xinit is a program that allows a user to manually start an X server. The startx script is a front-end for xinit. By default, xinit and

startx start an X server on display :0 and then start an xterm on it. When the xterm terminates, xinit and startx kill the X server. In general,

xinit and startx can start an arbitrary server and run an arbitrary script. Typically, this script runs a number of programs and a window manager. Arguments immediately following the startx command are used to start a client in the same manner as xinit. For example the startx -

- -dpi 100 command starts the xsession with 100 dpi.

The service and chkconfig commands are used to start and stop a service, and to ensure persistence across reboots. The service command is used to abstract the management of services provided by the system. It can be used to start and stop services, as well as to determine the status of services. To execute a given command for a given service, it uses the start, stop, restart, and reload arguments. Some important options used with the service command are as follows:

The chkconfig tool is used to update and query runlevel information for system services.

Answer option D is incorrect. The yum command automatically attempts to check all configured repositories to resolve all package dependencies during an installation/upgrade.

Answer option B is incorrect. The tape archive (tar) command combines a large number of files into a single file for archival purposes.

The VI is a visual interactive text editor that allows a user to create, modify, and store files on a Linux computer. It works in the following modes:

Command: This is the default mode of the command. Various commands can be used in this mode to manipulate the opened text.

Input: In this mode, a user can insert text directly in the text screen area.

Answer option D is incorrect. The GNU zip (GZIP) utility is a compression utility that is used to compress files for saving space. It creates files with the .gz extension. It can also compress tar files. In order to unzip files with the .gz extension, the

GUNZIP command is used.

Answer option B is incorrect. The nmap utility, also commonly known as port scanner, is used to view the open ports on a Linux computer. It is used by administrators to determine which services are available for external users. This utility helps administrators in deciding whether to disable the services that are not being used in order to minimize any security risk.

Answer option C is incorrect. MS Word is a Windows-based utility. Hence, it cannot be used in Linux.