RH033 Red Hat Linux Essentials Question and Answers

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

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.

If the package is not yet installed, the yum deplist httpd command is used to get the list of packages that httpd depends on.Answer option C is incorrect. The yum list httpd command can be used to list various information about available packages. For example, it lists all available and installed packages and all packages with updates available in the yum repositories.

Answer option D is incorrect. If the package is already installed, the rpm -qR httpd command is used to get the list of packages that this package depends on.

Answer option A is incorrect. This command is incorrect. The deplist option is not used with the rpm command.

According to the scenario, John will execute the foo && bar; command. Because of the && operator, bar will execute if and only if foo completes successfully.

Answer option C is incorrect. The foo; bar; command sequence will run foo and bar in a sequential manner, but the successful completion of the first command does not matter.

Answer option D is incorrect. The foo || bar; command sequence will run the bar if and only if foo fails to complete successfully.

Answer option B is incorrect. In the foo | bar; command sequence, the output of the foo command will be the input for the bar command.

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 ipconfig network diagnostic tool is used in the Windows operating system to see IP addresses and MAC addresses, and other related information. It is not used in the Linux operating system. In the place of the ipconfig utility, ifconfig is used in Linux for performing the same task.

Answer option D is incorrect. The ping utility is a network diagnostic tool that checks TCP/IP connectivity on any host. It is used in both Linux and Windows operating systems.

What is the ping utility?

The ping command-line utility is used to test connectivity with a host on a TCP/IP-based network.

This is achieved by sending out a series of packets to a specified destination host. On receiving the packets, the destination host responds with a series of replies. These replies can be used to determine whether or not the network is working properly.

Answer option A is incorrect. This is a network diagnostic tool in Linux that perform hostname to IP address translation and vice versa.

Answer option B is incorrect. This is a network diagnostic tool in Linux which is used to perform hostname to IP address translations, and vice versa in greater detail.

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 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,

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 -c option with the wc command is used to count the number of bytes in a file. It shows only the number of bytes used by a file.

Answer option A is incorrect. The -l option with the wc command is used to count the number of lines in a file. It shows only the number of lines in a file.

Answer option D is incorrect. The -w option with the wc command is used to count the number of words in a file. It shows only the number of words in a file.

Answer option C is incorrect. The -m option with the wc command is used to count the number of characters in a file.

The cal 7 2010 command will display the calendar of July 2010.

What is the cal command?

The cal command prints an ASCII calendar of the current month.

Syntax: cal [month] [year]

Given a month and year as arguments, cal displays the calendar for that particular month of the given year.

When a single numeric argument (such as 2005) is given, cal will display a calendar for the given year. Always use a fourdigit year. For example, the command cal 05 will display the calendar for the year 05, not the year

2005.

Answer option B is incorrect. The cal 20 July command will display only the month and year, and not the date.

Answer option A is incorrect. The cal command will display the calendar of the current month.

Answer option D is incorrect. The date command will display the current date and time of the system.

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

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 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.

The date command with the %M specifier prints the current time (Minutes). Since the output is redirected towards the date.txt file, the current time (Minutes) will be printed in the date.txt file.

The locate command queries a database for all pathnames that match the specified pattern. The specificity of locate can be increased by using it together with wildcards or other regular expressions. This command uses the star wildcard to display all files on the system that have the .xml filename extension.

What is a regular expression?

A regular expression is a way of describing a string of text using metacharacters or wildcard symbols.

For example, "*.xml" is a regular expression that refers to all files having the extension .xml.

What is a wildcard?

The specificity of LOCATE can be increased by using it together with wildcards or other regular expressions. Wildcards are characters that can be used to substitute for any other character or characters. For example, the star character (*) is a wildcard that can represent any single character or any string containing any number of characters.

Answer option A is incorrect. This is an incorrect syntax and an error messages will be displayed.

Answer option D is incorrect. The cat command displays the content of the specified file.

Answer option B is incorrect. This is an incorrect command, when you type this command an error message will be displayed.

The inode table contains the last access time, last modification time as well as the last inode change time of a file.

What type of data is stored in an inode table?

An inode table contains a list of all files in an ext2 and ext3 filesystem. An inode ( index node) is an entry in the table, containing information about a file (the metadata). Some important data stored in the inode table are as follows:

The file type (regular file, directory, etc.)

File permissions

Link count: The number of file names associated with the inode number.

The user ID number of file owner and the group ID number of the associated group.

Timestamps, including last access time, last modification time, and last inode change time.

Location of the data on the hard disk.

Answer options D, B, and A are incorrect. The inode table contains all these information, the file type, file permissions on the specified file, location of data on the hard disk.

The default tool for email and groupware in Red Hat Enterprise Linux is called Evolution. Evolution provides not only the email access, but also the ability to maintain a calendar, tasklist and contacts database.

What is Evolution?

Evolution is a full-featured personal and workgroup information management tool for Linux systems, and is the default email client for Red Hat Enterprise Linux. It provides all of the standard email client features, including powerful mailbox management, user-defined filters, and quick searches. Its additional feature is a flexible calendar/scheduler, which allows users to create and confirm group meetings and special events online.

Answer option C is incorrect. Thunderbird is a graphical mail client that offers email, Usenet and rss support but it does not support groupware features. Thunderbird is provided along with Firefox and others as part of the Mozilla suit of application.

What is groupware?

Groupware refers to programs that help users work together collectively while located remotely from each other.

Groupware services can include the sharing of calendars, collective writing, e-mail handling, shared database access, electronic meetings with each user able to see and display information to others, and other activities. Sometimes called collaborative software, groupware is an integral component of a field of study known as Computer-

Supported Cooperative Work or CSCW.

Answer options A and D are incorrect. The mutt and pidgin are Non-GUI mail clients.

What is mutt? mutt is a powerful tool for managing email within a text-only environment. This tool is very important to access email even when a graphical interface is not available. Some of its strengths are handling of message threads and flexibility. When mutt sees a series of related messages, it displays each reply under the parent. mutt supports sending of attachments through a mail. The following example describes how a file can be attached to a mail: echo "Sending an attachment." | mutt -a backup.zip -s "attachment" local@domain.com

This command will send a mail to local@domain.com with the subject (-s) "attachment", the body text "Sending an

attachment.", containing the attachment (-a) backup.zip.

What is Pidgin?

Pidgin is a multi-protocol Instant Messaging client that allows a user to use all of his IM accounts at once. It is a free software that can work with AIM ,Gadu-Gadu, Jabber, ICQ ,IRC, MSN, SILC, XMPP, Yahoo!, and Zephyr Network. Anyone is

free to use it and modify it, but if a user distributes his modifications, he must distribute the modified source code as well.

The license of this communication software is Freeware, i.e. anyone can freely download and use this communication software.

When a user types alias c= 'clear' on the command prompt and presses Enter this will create an alias for the clear command. After creating the alias whenever a user wants to clear the screen, he just needs to type c and then press Enter.

This action will clear the screen. This alias will be lost if a user logs out and logs in again.

What is the alias command?

The alias command is a shortcut name for longer commands. If a command is run often, but it takes a considerable amount of time in typing that command, the time can be reduced by using the alias command.

For example: # alias list= 'ls-la'

This will create an alias called list, which will use the ls command to print a long-style listing of all files in the current directory (the -l gives a long-style list, and the -a shows all files -including hidden files).

Answer options B, C, and A are incorrect. These are incorrect commands and will show error messages on the command prompt.