Free Practice Questions for LPI 102-500 Exam

The xwininfo command is a utility for displaying information about windows on an X server. One of the information it displays is the depth of the window, which is the number of bits per pixel used to represent the color of the window. The depth of the root window, which is the background window of the X server, is the same as the color depth of the X server. To display the depth of the root window, one can use the command xwininfo -root and look for the line that says “depth of root window”. Alternatively, one can use the command xdpyinfo, which displays information about the X server, and look for the line that says “depths of root window”. References:

xwininfo(1) - Linux man page

xdpyinfo(1) - Linux man page

[LPI Linux Certification/Configure the X Window System, Xorg and …]

The command that can be used to show the current color depth of the X Server is xwininfo. xwininfo is a command-line tool that provides information about X windows. When executed, it opens a small window and waits for the user to select a window by clicking on it. Then, it displays various characteristics about the window in question, such as its geometry, position, size, depth, class, name, id, and more. The depth value indicates the number of bits per pixel used to represent the colors of the window. xwininfo is part of the X Window System, which is a graphical user interface system for Unix-like operating systems. xwininfo can be useful for debugging, testing, or scripting purposes.

The other options are incorrect because they are either invalid commands or do not show the color depth of the X Server:

xcd is not a valid command in Linux. It may be confused with cd, which is used to change the current working directory.

xcdepth is not a valid command in Linux. It may be confused with xrandr, which is used to change the screen resolution and orientation.

xcolordepth is not a valid command in Linux. It may be confused with xcalib, which is used to load, alter, and query the color profile of the X display.

cat /etc/X11 is not a command, but a directory. cat is used to concatenate files and print them to the standard output. /etc/X11 is a directory that contains configuration files for the X Window System. However, these files do not necessarily show the current color depth of the X Server, as it may be overridden by other settings or options. References:

https://bing.com/search?q=command+to+show+color+depth+of+X+Server

https://x.org/releases/X11R7.5/doc/man/man5/xorg.conf.5.html

The xhost program is used to add and delete host names or user names to the list allowed to make connections to the X server1. In the case of hosts, this provides a rudimentary form of privacy control and security. It is only sufficient for a workstation (single user) environment, although it does limit the worst abuses1. However, if xhost is used to grant access to everyone, even if they aren’t on the list (i.e., access control is turned off), then any user on the network can connect to your X server and monitor your keystrokes, capture your screen, or run malicious programs2. This is why xhost is considered dangerous to use and should be avoided in favor of more secure methods, such as xauth or ssh23. References:

xhost linux command man page - commandlinux.com

Linux Xhost Command Help and Examples - Computer Hope

xhost(1) — Arch manual pages

The command that can be used to investigate the properties for a particular window in X by clicking that window is xwininfo. xwininfo is a command-line tool that provides information about X windows. When executed, it opens a small window and waits for the user to select a window by clicking on it. Then, it displays various characteristics about the window in question, such as its geometry, position, size, depth, class, name, id, and more. xwininfo is part of the X Window System, which is a graphical user interface system for Unix-like operating systems. xwininfo can be useful for debugging, testing, or scripting purposes. References: https://bing.com/search?q=command+to+investigate+properties+of+a+window+in+X

https://www.exam-answer.com/linux-foundation-certified-system-administrator-lfcs-simulation-investigate-window-properties

The X11 configuration file xorg.conf is grouped into sections, and the content of the section SectionName is associated with that section by placing it between a line containing Section “SectionName” and a line containing EndSection. For example, the following is a section named ServerLayout that defines the layout of the X server:

Section “ServerLayout” Identifier “X.org Configured” Screen 0 “Screen0” 0 0 InputDevice “Mouse0” “CorePointer” InputDevice “Keyboard0” “CoreKeyboard” EndSection

The other options are incorrect for the following reasons:

A: Curly brackets are not used to delimit sections in xorg.conf. They are used to enclose values that are lists, such as Option “XkbLayout” “{us,fr}”.

C: Tags are not used to delimit sections in xorg.conf. They are used in XML files, which have a different syntax and structure than xorg.conf.

D: Rows are not used to delimit sections in xorg.conf. They are used to define key-value pairs within a section, such as Identifier “Screen0”.

E: Indentation is not required to delimit sections in xorg.conf. It is used to improve readability and clarity, but it does not affect the functionality of the file.

References:

xorg.conf - X Window System

Editing basics for the xorg.conf file - Linux.com

106.1 Lesson 1 - Linux Professional Institute Certification Programs

The xwininfo command is a utility for displaying information about windows in X. It can show various attributes of a window, such as its location, size, depth, border width, visual class, colormap, map state, and event masks. The -metric option specifies that all dimensions should be displayed in metric units (millimeters) rather than pixels. By issuing the xwininfo -metric command and then clicking on a window, the administrator can determine the geometry of that window, including the decorations, in millimeters. References:

xwininfo(1) — Arch manual pages

[command line -

The /etc/cron.allow and /etc/cron.deny files are used to control access to the crontab command and cron jobs for individual users. If neither of these files exists, then depending on site-dependent configuration parameters, only the superuser (root user) will be allowed to use this command, or all users will be able to use this command1. The default behavior of most Linux distributions is to allow all users to use the crontab command and have user specific crontabs if neither /etc/cron.allow nor /etc/cron.deny exists23. Therefore, option B is the correct answer. The other options are not true because:

Option A is false because it contradicts the default behavior of most Linux distributions.

Option C is false because the cron daemon will not refuse to start or report missing files in the system’s logfile if neither /etc/cron.allow nor /etc/cron.deny exists. The cron daemon will start normally and use the default configuration parameters1.

Option D is false because the system administrator does not need to approve user specific crontabs explicitly. The user can create, edit, display, or remove their own crontab files without any intervention from the system administrator1. References:

How cron.allow and cron.deny can be used to limit access to crontab for a particular user | The Geek Search

crontab(1) — cron — Debian bullseye — Debian Manpages

Controlling Access to crontab (System Administration Guide: Basic Administration) - Oracle

/etc/cron.allow - Linux Bash Shell Scripting Tutorial Wiki - nixCraft

Running the command chsh -s /bin/false with the user name will change the user’s login shell to /bin/false, which is a program that does nothing and returns a non-zero exit code. This means that the user will not be able to execute any commands or start an interactive shell session. This is a common way to disable a user’s login without disabling the account completely, which can be useful for users who only need to access the system via scp, sftp, or other non-interactive services. However, this method does not prevent the user from authenticating with the system, and it may not work with some services that do not rely on the login shell, such as ssh with a forced command. Therefore, it is not a foolproof way to secure the system from unauthorized access. References: 1234

The crontab file format consists of six fields: minute, hour, day of month, month, day of week, and command. The user-specific crontab files have the same format as the global /etc/crontab file, except that they do not have the username field. The username field is only present in the system-wide crontab files and specifies which user will run the cron job. The year field is not a valid crontab field and is not supported by cron. References:

Scheduling Cron Jobs with Crontab | Linuxize

Crontab Explained in Linux [With Examples]

The TZ environment variable is used to change the time zone for the commands run from within the environment variable’s scope. It specifies the name of a time zone as defined in the /usr/share/zoneinfo directory or a custom time zone in the POSIX format12. The TZ variable can be set either globally in a shell profile file or locally in a shell session. For example, to set the time zone to America/New_York for the current shell session, one can use the following command:

export TZ=America/New_York

To verify the change, one can use the date command to display the current date and time according to the TZ variable. The TZ variable can also be used to run a single command with a different time zone without affecting the system’s time zone. For example, to run the date command with the Asia/Tokyo time zone, one can use the following syntax:

TZ=Asia/Tokyo date

The TZ variable is useful for testing how applications behave in different time zones or for displaying the time in different locations34. References:

How to Set or Change the Time Zone in Linux | Linuxize

Linux / UNIX: TZ Environment Variable - nixCraft

Get Current System Time Zone in Linux | Baeldung on Linux

Setting the TZ Environment Variable on Linux | InterSystems Developer