LPI 010-160 Linux Essentials Certificate Exam, version 1.6 Exam Dumps and Practice Test Questions Set 7 Q91-105
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Question 91
Which command in Linux is used to check the available free memory?
A) free
B) ps
C) top
D) vmstat
Answer: A) free
Explanation
The free command in Linux is used to check the available free memory on the system. It displays the total, used, free, shared, buffer/cache, and available memory in a system. This is one of the most common commands for quickly checking how much memory is being used and how much is free, making it a valuable tool for system administrators and users who need to monitor memory usage.
When you run the free command, it typically displays output similar to the following:
Total: This is the total amount of physical RAM installed in the system.
Used: The amount of RAM that is currently being used by running processes.
Free: The amount of RAM that is currently not in use by any processes.
Shared: The amount of RAM that is being shared between processes.
Buffer/Cache: Memory used by the system for caching data and buffering I/O operations.
Available: The amount of memory available for use by processes, factoring in memory that can be reclaimed from caches and buffers.
The free command provides an overview of memory usage, which can be particularly useful for troubleshooting or understanding how much memory your system has available at any given time. By using the -h option, you can display the output in a more human-readable format (e.g., in MB, GB) instead of in kilobytes, which is the default unit of measurement.
The second option, ps, is a command used to display information about processes running on the system, not memory usage. While ps provides information such as the PID, memory usage, and CPU usage for individual processes, it does not provide a summary of overall system memory usage like free does.
The third option, top, is another command that can display system memory usage, but it is a real-time tool that continuously updates the display with information about CPU and memory usage. While top provides detailed, continuously updated resource usage statistics, it is more useful for monitoring resource consumption over time rather than getting a one-time snapshot of memory usage, which free excels at.
The fourth option, vmstat, stands for virtual memory statistics. It provides information about system processes, memory, paging, block IO, traps, and CPU activity. Although it can show memory statistics, vmstat is primarily focused on system performance and is less commonly used for checking available free memory in comparison to the free command.
Thus, the free command is the best choice for quickly checking the available free memory on the system. It provides a clear and concise summary of memory usage and is an essential tool for system monitoring.
Question 92
What command would you use to display the manual pages for a command in Linux?
A) man
B) help
C) info
D) page
Answer: A) man
Explanation
The man command is used in Linux to display the manual pages (manuals) for other commands. The manual pages provide detailed documentation for commands, their syntax, options, and examples of usage. The man command is one of the most frequently used tools for learning about other commands and understanding how they work.
For example, if you wanted to learn more about the ls command (which lists files and directories), you would run the following command:
man ls
This would display the manual page for the ls command, which explains its various options (e.g., -l for long format, -a for all files) and provides additional details on how to use it effectively.
The man command supports navigation using the arrow keys, and you can search for specific terms within the manual page using the / key. To exit the manual page viewer, you simply press q.
The help command is another way to get information about Linux commands, but it typically only provides a brief overview of the command’s syntax and options. For example, running help ls will provide a short summary of how to use the ls command, but it will not offer the same level of detailed information that the man command does.
The info command is used to display documentation for commands, but it generally provides a different style of documentation, sometimes more detailed than man pages and sometimes organized differently. While info is useful, it is not as universally available as man, and many commands do not have info pages.
The fourth option, page, is not a valid command in Linux. There is no page command used for viewing manuals or documentation.
The man command is the most widely used method for accessing command documentation in Linux and should be your go-to tool for learning about any Linux command.
Question 93
Which command is used to change the current working directory in Linux?
A) ls
B) cd
C) pwd
D) mv
Answer: B) cd
Explanation
The cd (change directory) command is used in Linux to change the current working directory. This command allows users to navigate the filesystem by specifying the directory they wish to work in. After executing the cd command with the desired directory path, the terminal session’s current working directory changes to the specified location.
For example, if you are in the home directory and want to navigate to the /var/log directory, you would use the following command:
cd /var/log
After running this command, the terminal’s current directory will be /var/log, and any subsequent commands will operate within that directory until you change the directory again with cd.
You can also use cd to navigate relative to the current directory. For instance, if you are currently in /home/user and want to move to the Documents directory inside it, you would type:
cd Documents
Additionally, cd .. is used to move up one directory level, meaning it will take you to the parent directory of your current directory.
The ls command is used to list the contents of a directory. It does not change the current directory but helps you see what files and subdirectories are available in the directory you are currently in.
The pwd command stands for print working directory, and it is used to display the current working directory. It shows the full path of the directory you are currently in but does not change it. pwd is helpful when you want to know where you are in the filesystem.
The mv command is used for moving or renaming files and directories. It does not change the current working directory but instead allows you to move files from one directory to another or rename them. For example, you could use mv file1.txt /home/user/Documents to move file1.txt to the /home/user/Documents directory.
Thus, the cd command is the correct one for changing the current working directory in Linux. It is a fundamental command for navigation within the filesystem and essential for working in different directories.
Question 93
Which command is used to change the current working directory in Linux?
A) ls
B) cd
C) pwd
D) mv
Answer: B) cd
Explanation
The cd (change directory) command is used in Linux to change the current working directory. The Linux file system is organized in a hierarchical structure, and cd allows users to navigate this structure to access different directories or subdirectories.
When you execute cd with a directory path, it changes your working directory to the specified location. For example, if you are currently in the /home/user directory and you want to go to /var/log, you would use the command:
cd /var/log
After executing this command, your current working directory is now /var/log, and any subsequent commands you run will be relative to this directory. If you want to go to the parent directory (one level up), you can use the cd .. command. This command moves you from your current directory to its immediate parent directory. For instance, if you are in /home/user/Documents, running cd .. will take you to /home/user.
cd can also be used with relative paths. For example, if you are in /home/user and want to navigate to Documents within that directory, you can simply use cd Documents. If the directory does not exist, cd will return an error message.
The ls command, listed as option A, is used to list the contents of a directory, not to change the current directory. ls will show files and subdirectories within the directory you are currently in, but it doesn’t allow you to move to a different directory.
The pwd command, option C, stands for print working directory, and it displays the full path of the current working directory. It is useful for verifying where you are in the file system but does not allow you to change directories.
The mv command, option D, is used for moving or renaming files and directories. It does not change the working directory. Instead, it allows you to move a file from one location to another or rename a file or directory. For example, mv oldfile.txt newfile.txt renames oldfile.txt to newfile.txt. It’s important to note that mv does not navigate directories.
Therefore, the cd command is the correct command to change the current working directory. It is a critical tool for navigation in the Linux file system and is frequently used to move between directories.
Question 94
Which of the following commands in Linux is used to view disk usage for a specific directory?
A) df
B) du
C) ls
D) fdisk
Answer: B) du
Explanation
The du (disk usage) command in Linux is used to view the disk usage of specific files and directories. This command is helpful for determining how much disk space a directory and its contents are consuming. Unlike df, which provides information about the total space used on mounted filesystems, du gives a detailed view of the storage usage within a specific directory.
By running du on a directory, it recursively calculates and displays the total disk space used by that directory and all of its subdirectories. For example, if you want to find out how much space the /home/user/Documents directory is using, you would run:
du /home/user/Documents
This command will list the disk usage for each subdirectory inside /home/user/Documents, as well as the total disk usage for the entire directory.
To make the output easier to read, you can use the -h option to display the disk usage in a human-readable format, such as kilobytes (KB), megabytes (MB), or gigabytes (GB). Running the following command would make the output more intuitive:
du -h /home/user/Documents
For example, the output might look like this:
4.0K /home/user/Documents/dir1
8.0K /home/user/Documents/dir2
12K /home/user/Documents
This indicates that dir1 uses 4 KB, dir2 uses 8 KB, and the total size of the /home/user/Documents directory is 12 KB.
The df command, listed as option A, is used to display the disk space usage of the entire filesystem. While df shows the available, used, and total space of mounted filesystems, it does not provide detailed information about the usage of individual directories or files. It’s more about the overall system storage than a directory’s specific usage.
The ls command, option C, is used to list files and directories in the current directory. While you can use ls -lh to see the size of individual files, it does not provide a summary of the total disk usage for a directory. It’s more focused on listing directory contents rather than calculating disk usage.
The fdisk command, option D, is used to manage disk partitions. It allows you to create, delete, and modify partitions on a disk. fdisk is not concerned with disk usage or file space. Instead, it deals with partitioning tasks, which are different from monitoring disk usage.
Therefore, the correct command to view disk usage for a specific directory is du. It provides a detailed breakdown of disk space usage and is an essential tool for administrators and users who need to monitor disk space consumption at a granular level.
Question 95
Which command is used to display the system’s hostname in Linux?
A) uname
B) hostname
C) sysctl
D) ip
Answer: B) hostname
Explanation
The hostname command is used to display or set the system’s hostname in Linux. A hostname is the name that identifies a machine on a network. It is an essential part of the system’s configuration and is used by other systems to identify this machine over a network. The hostname command can be used to display the current system hostname or set a new one.
For example, running the following command will show the current hostname of the system:
hostname
This will display just the name of the system, such as mycomputer, without any additional details.
To set a new hostname temporarily (it will revert after a reboot), you can use the hostname command followed by the new name:
hostname newname
The new hostname will be applied immediately but will not persist after a reboot unless it is also updated in the system’s configuration files (such as /etc/hostname).
The uname command, listed as option A, is used to display system information, including the kernel name, version, and architecture. While uname -n can show the hostname, it is primarily used for kernel and system information, not specifically for displaying the hostname in a user-friendly format.
The sysctl command, option C, is used to configure kernel parameters at runtime. It allows you to view and modify system settings related to networking, memory management, and other kernel features. sysctl does not display the system hostname.
The ip command, option D, is used for network configuration tasks, such as displaying or modifying network interfaces and routing tables. While ip a displays information about network interfaces, it does not provide the system’s hostname.
Therefore, the correct command to display the system’s hostname is hostname. It provides the name of the machine as recognized by the network, which is crucial for network identification and communication.
Question 96
Which command in Linux is used to display the last few lines of a file?
A) cat
B) tail
C) head
D) less
Answer: B) tail
Explanation
The tail command in Linux is used to display the last few lines of a file. It is commonly used for monitoring log files or viewing the end of a large file when you only need the most recent entries. By default, tail shows the last 10 lines of a file, but you can customize the output to show a different number of lines if needed.
For example, if you want to view the last 10 lines of a file called logfile.txt, you would run the command:
tail logfile.txt
If you want to display a specific number of lines, you can use the -n option. For example, to display the last 20 lines, you would run:
tail -n 20 logfile.txt
Additionally, the tail command is often used in conjunction with the -f option to monitor log files in real-time. When you use tail -f, it continuously updates the output with new lines as they are added to the file, making it ideal for tracking ongoing logs or process output.
The cat command, listed as option A, is used to concatenate and display the contents of a file. While cat can display the entire contents of a file, it does not specifically focus on the last few lines. cat is typically used for smaller files or for concatenating multiple files into one output, rather than for viewing the end of a file.
The head command, option C, is the opposite of tail. It is used to display the first few lines of a file, not the last few. By default, head shows the first 10 lines of a file, but like tail, you can use the -n option to customize the number of lines displayed.
The less command, option D, is a pager utility used to view large files interactively. While less can be used to scroll through a file and move to the end, it does not specifically show only the last few lines of a file unless you navigate to the end manually. less is often used for navigating through long files, but for simply viewing the last few lines, tail is more efficient.
Therefore, the tail command is the best option for displaying the last few lines of a file. It is particularly useful for monitoring logs or any file where you need to view the most recent data added.
Question 97
What is the purpose of the chmod command in Linux?
A) Change file ownership
B) Change file permissions
C) Change file contents
D) Change the file’s name
Answer: B) Change file permissions
Explanation
The chmod command in Linux is used to change file permissions. In Linux, every file and directory has associated permissions that control who can read, write, or execute the file. The chmod command allows users to modify these permissions.
Permissions in Linux are represented by three types of access for three categories of users:
Owner: The user who owns the file.
Group: The group that the file belongs to.
Others: All other users who are not the owner or members of the group.
Permissions can be represented numerically or symbolically:
Read (r): Allows viewing the file.
Write (w): Allows modifying the file.
Execute (x): Allows executing the file as a program or script.
For example, the command:
chmod u+x file.txt
adds the execute permission to the file file.txt for the user (owner).
Permissions can be set for the owner, group, and others using symbolic notation (like rwx for read, write, and execute) or numerical values. The numbers used in chmod represent the permission settings:
4 = read
2 = write
1 = execute
So, a permission of 7 (read, write, and execute) is represented as rwx.
For example:
chmod 755 file.txt
This would set the file permissions so that the owner has full permissions (read, write, execute), and the group and others can read and execute the file but cannot modify it.
The chown command, listed as option A, is used to change the ownership of a file, not the permissions. While chmod modifies the file’s permissions, chown changes who owns the file and the group associated with it.
The vi or nano commands are used to edit the contents of a file. They are text editors, not related to changing the file’s permissions or ownership.
The mv command, listed as option D, is used to rename or move files. It does not change file permissions. Instead, mv is for modifying the file’s location in the filesystem or renaming it.
Therefore, chmod is the correct command for changing file permissions, enabling users to control who can read, write, or execute their files.
Question 98
Which command is used to display the IP address configuration of a Linux system?
A) ipconfig
B) ifconfig
C) netstat
D) route
Answer: B) ifconfig
Explanation
The ifconfig command in Linux is used to display the IP address configuration of a network interface on the system. It shows information about the active network interfaces, including their IP addresses, MAC addresses, and other relevant details such as network statistics, broadcast addresses, and network masks.
For example, running the following command:
ifconfig
will display the IP address configuration for all active network interfaces on the system, such as eth0, wlan0, or lo (loopback interface). The output will include information about the IP address, netmask, and other settings related to the interface.
While ifconfig is still widely used, it is considered deprecated in some Linux distributions in favor of the ip command. The ip command provides more advanced and comprehensive network configuration options, but ifconfig remains a common tool for quickly checking the IP address configuration.
The ipconfig command, listed as option A, is used in Windows operating systems, not Linux. It serves a similar purpose to ifconfig by displaying network configuration information, but it is specific to the Windows environment and cannot be used on Linux.
The netstat command, option C, is used for network statistics, including displaying active network connections, routing tables, and interface statistics. While netstat provides information about network connections and traffic, it does not specifically display the IP address configuration of the system.
The route command, option D, is used to view or modify the system’s routing table. It shows how network traffic is routed from one network interface to another but does not provide detailed information about the IP address configuration of the system’s interfaces.
Therefore, ifconfig is the correct command for displaying the IP address configuration on a Linux system. While other commands like netstat and route are useful for networking tasks, ifconfig remains the most straightforward option for checking the system’s IP address and related network settings.
Question 99
What is the purpose of the grep command in Linux?
A) To display system information
B) To search for patterns in a file
C) To list the contents of a directory
D) To monitor system processes
Answer: B) To search for patterns in a file
Explanation
The grep command in Linux is a powerful tool used for searching for patterns in a file or the output of other commands. It is one of the most frequently used commands for searching through files to find specific text, whether it’s a single word, a phrase, or even a regular expression pattern.
The basic syntax of grep is:
grep pattern filename
For example, if you wanted to search for the word «error» in a file called log.txt, you would run:
grep «error» log.txt
This will search for occurrences of the word «error» in the log.txt file and display the lines containing that word. By default, grep performs a case-sensitive search, but you can modify this behavior using various options. For instance, the -i option makes the search case-insensitive.
grep also supports regular expressions. This allows you to perform complex pattern matching, which can be useful when searching for variable strings or specific formats (such as IP addresses or dates).
One of the most useful features of grep is its ability to search through the output of other commands by using piping. For example, to find processes with the word «apache» in their name, you can pipe the output of ps aux into grep:
ps aux | grep apache
This will show only the lines containing the word «apache», which is extremely useful for finding processes or filtering large amounts of data.
The ls command, listed as option C, is used to list the contents of a directory. It does not search files or patterns. While ls can be combined with other commands (such as grep) to filter the output, ls by itself is not a search tool.
The top command, listed as option D, is used to monitor system processes and display real-time information about CPU and memory usage. While top is useful for monitoring system performance, it does not search for text or patterns within files.
The uname command, option A, displays system information about the operating system, kernel version, and hardware architecture. While useful for gathering details about the system, uname is not used for searching within files.
Therefore, the grep command is the correct answer. It is a highly versatile tool that allows users to search for specific text patterns in files, outputs from other commands, or even entire directories.
Question 100
What does the ps command do in Linux?
A) Displays the running processes
B) Displays the disk usage
C) Displays the current directory
D) Displays system logs
Answer: A) Displays the running processes
Explanation
The ps command in Linux is used to display information about running processes on the system. A process is any program or task that is running in the system, and ps helps you view details about those processes, such as their process IDs (PIDs), CPU and memory usage, and the command used to start them.
The ps command by itself typically shows information about processes running in the current terminal session. For example, running ps will display a list of processes started by the current user in that terminal.
A more commonly used version of the command is ps aux, which shows all running processes across the system, including those started by other users. This command displays a variety of information, including:
USER: The owner of the process.
PID: The process ID.
%CPU: The percentage of CPU the process is using.
%MEM: The percentage of memory the process is using.
VSZ: The virtual memory size of the process.
RSS: The resident set size, or the non-swapped physical memory the process is using.
COMMAND: The command that started the process.
The ps command can be combined with other options to display more specific information or format the output. For example, ps -ef provides detailed information about every running process in a standard format, and ps -aux can be useful for more general overviews of the system’s process state.
Option B, df, is used to display disk usage statistics, showing the amount of space used and available on mounted filesystems. It is not related to viewing running processes.
Option C, pwd, is used to print the current working directory. It shows the absolute path of the directory you’re currently in, but it does not provide information about running processes.
Option D, journalctl, is used to view system logs generated by systemd. It helps you view logs related to system services and other processes, but it is not used for viewing running processes.
Therefore, the ps command is the correct answer because it provides information about processes that are currently running on the system. It’s essential for monitoring and managing system processes.
Question 101
What command is used to display the IP routing table in Linux?
A) route
B) ip
C) netstat
D) ifconfig
Answer: A) route
Explanation
The route command in Linux is specifically designed to display and manage the system’s IP routing table. The routing table is a critical component of any networked system, as it defines how network traffic is directed from the local machine to other devices or networks. Essentially, it serves as a roadmap that tells the operating system where to send packets of data depending on their destination IP addresses. This command is widely used by system administrators, network engineers, and advanced users to inspect, verify, and troubleshoot routing configurations. The routing table contains key information such as the destination networks, the gateways through which traffic should be routed, the network interfaces to be used for each route, and the metrics or priorities assigned to individual routes. Metrics are particularly important because they determine which route is preferred when multiple routes to the same destination exist. Lower metric values generally indicate higher priority routes, allowing the kernel to make intelligent decisions about packet delivery. Understanding and managing the routing table is essential for ensuring that data is transmitted efficiently and accurately across networks, and the route command provides the necessary visibility and control.
To view the routing table using the route command, a user can simply enter the command without any additional arguments. Running the command in this way will produce an output that lists all current routes configured in the system, including the default route. The default route is particularly significant because it acts as a catch-all path for packets destined for networks not explicitly listed in the routing table. In most cases, the default route points to the system’s primary gateway, which then forwards the traffic to external networks or the internet. Each entry in the routing table shows the destination network, the gateway through which packets are sent, the associated network interface, and the metric. This information allows administrators to understand exactly how data flows through the system and ensures that network communication occurs as intended. For troubleshooting purposes, being able to view the routing table in a clear, structured format is indispensable.
In addition to the basic command, the route command supports several options to customize the output. One commonly used option is -n, which displays the routing table using numeric IP addresses rather than attempting to resolve hostnames. This is useful because DNS resolution can introduce delays or confusion, especially in large networks where hostnames may be unfamiliar or improperly configured. Using route -n produces a cleaner, faster output that allows users to immediately see the destination addresses, gateways, and interfaces without waiting for hostname resolution. This numeric display is particularly valuable in troubleshooting scenarios, where speed and accuracy are critical. The -n option is widely adopted in scripts, automated monitoring tools, and diagnostic procedures to quickly assess the routing configuration and verify connectivity between systems.
While the route command has been historically popular and remains widely recognized, it is important to note that it is considered deprecated on modern Linux distributions in favor of the ip command from the iproute2 suite. The ip command provides a more modern and versatile approach to network configuration and management, including routing. Using ip route, for example, administrators can view routing tables, add or remove routes, and manipulate route attributes in ways that the older route command does not support. The ip command offers finer-grained control and better integration with contemporary Linux networking features, making it the preferred tool for new systems. Despite this, the route command is still used in legacy scripts and documentation, and understanding it is essential for administrators working with older systems or studying Linux networking fundamentals.
Other commands often considered in the context of network management include netstat and ifconfig, but these serve different purposes. The netstat command is primarily used to display network statistics and active connections. It provides information about which ports are open, which services are listening, and the status of established connections. While netstat is extremely useful for monitoring active traffic and diagnosing connection issues, it does not provide visibility into the routing table, and thus cannot be used to determine how packets are routed across networks. Similarly, the ifconfig command is used to display and configure network interface information. It shows details such as the IP addresses assigned to each interface, interface status, MAC addresses, and basic statistics about transmitted and received packets. While this is valuable for interface-level diagnostics and configuration, it does not provide information about routing paths or default gateways. Understanding the distinction between these commands is important because each serves a specific aspect of network management, and using the correct tool for the intended task ensures accurate analysis and troubleshooting.
Analyzing these commands demonstrates that while several network-related tools exist, only the route command is specifically intended to display the IP routing table. It provides the critical information needed to understand how the system directs traffic, including gateways, interfaces, and routing metrics. By using route or its modern counterpart, ip route, administrators can inspect, verify, and troubleshoot network configurations, ensuring proper connectivity and optimal traffic flow. This functionality makes the route command an essential tool for network management and diagnostic tasks on Linux systems.
Question 102
Which of the following commands is used to display the currently mounted filesystems in Linux?
A) df
B) mount
C) lsblk
D) blkid
Answer: B) mount
Explanation
The mount command in Linux is used to display the currently mounted filesystems. A mounted filesystem refers to a file system that has been attached to the system’s directory tree so that the operating system can access and manipulate files stored on a device or storage media. The mount command is crucial for managing disk partitions, network shares, and removable media such as USB drives.
When you run the mount command without any arguments, it displays a list of all filesystems that are currently mounted on the system. The output will include:
The device or partition that has been mounted.
The mount point (the directory where the filesystem is attached).
The filesystem type (e.g., ext4, ntfs).
Mount options (e.g., read-only, noexec).
Other information, such as the device’s label and UUID.
For example, the output might look like this:
/dev/sda1 on / type ext4 (rw,relatime,data=ordered)
/dev/sdb1 on /mnt/usb type vfat (rw,nosuid,nodev,uid=1000)
This tells us that /dev/sda1 is mounted on the root directory / and uses the ext4 filesystem, while /dev/sdb1 is mounted on /mnt/usb and uses the vfat filesystem.
Option A, df, is used to display disk space usage. While it provides information about the total space, used space, and available space on mounted filesystems, it does not list the devices or partitions themselves, nor does it provide detailed information about the mount points.
Option C, lsblk, is used to list information about block devices. It shows details about disks, partitions, and storage devices, including their size, type, and mount points, but it does not explicitly show information about the currently mounted filesystems in the same format as the mount command.
Option D, blkid, is used to display information about block devices like partition types, UUIDs, and labels. It is typically used for identifying and labeling partitions but is not focused on showing the current mount status of filesystems.
Therefore, the mount command is the correct choice for displaying the currently mounted filesystems, as it provides detailed and specific information about each filesystem and its mount point.
Question 103
Which command is used to change the ownership of a file in Linux?
A) chown
B) chmod
C) chgrp
D) mv
Answer: A) chown
Explanation
The chown command in Linux is used to change the ownership of a file. Ownership of a file determines which user or group has control over the file and its associated permissions. This control is important for managing access to files and directories on the system.
The basic syntax of the chown command is:
chown [new-owner] [new-group] filename
For example, to change the owner of the file document.txt to the user alice and the group to admin, you would use the following command:
chown alice:admin document.txt
You can also specify only the owner or the group separately:
To change just the owner: chown alice document.txt
To change just the group: chown :admin document.txt
The chown command requires superuser (root) privileges to change the ownership of a file to a different user or group. A regular user can only change ownership to themselves or their own group, but changing ownership to another user or group requires sudo permissions.
The chmod command, listed as option B, is used to change file permissions, not ownership. chmod allows users to modify read, write, and execute permissions for the owner, group, and others, but it does not change who owns the file.
The chgrp command, option C, is used to change the group ownership of a file. While chgrp can be used to modify the group associated with a file, it does not affect the user ownership.
The mv command, option D, is used to move or rename files, not to change ownership. While mv allows you to move files between directories or rename them, it does not change the ownership or group ownership of the file.
Therefore, chown is the correct command for changing the ownership of a file in Linux. It gives administrators the ability to assign control over files and directories to different users and groups.
Question 104
Which command is used to create an empty file in Linux?
A) touch
B) mkfile
C) newfile
D) create
Answer: A) touch
Explanation
The touch command in Linux is used to create an empty file. It is one of the simplest and most common ways to create a new file without adding any content to it. The primary function of touch is to change the timestamp of a file — if the file already exists, it updates its last access and modification times. If the file does not exist, touch will create an empty file with the specified name.
For example, running the following command:
touch newfile.txt
will create an empty file named newfile.txt in the current directory. If the file already exists, touch will not modify its contents but will update its modification timestamp to the current time.
The touch command is very useful for quickly creating placeholder files or updating the timestamp of a file that has not been accessed or modified recently. You can also use it to create multiple files at once by providing a list of file names:
touch file1.txt file2.txt file3.txt
Option B, mkfile, is not a valid Linux command. It is found in other Unix-like systems (such as Solaris) but does not exist in Linux. Linux uses touch to create empty files instead.
Option C, newfile, is also not a valid command in Linux. There is no newfile command for creating files.
Option D, create, is not a recognized Linux command for creating files. In Linux, file creation is typically handled by touch, echo, or text editors like vi or nano if you want to create a file and edit it simultaneously.
Therefore, touch is the correct command for creating empty files in Linux. It’s simple, effective, and widely used for file creation and timestamp management.
Question 105
Which command is used to display a list of all users currently logged into a Linux system?
A) who
B) useradd
C) w
D) users
Answer: A) who
Explanation
The who command in Linux is used to display a list of all users currently logged into the system. This command shows information about users who are logged in, including their usernames, the terminal they are logged into, their login time, and the IP address or hostname from which they logged in.
For example, running:
who
might produce output like this:
alice tty1 2023-10-01 08:45
bob pts/0 2023-10-01 09:15 (192.168.1.5)
In this example:
alice is logged into the local terminal tty1 since 8:45 AM.
bob is logged into the remote terminal pts/0 from the IP address 192.168.1.5.
This command provides essential information about the users currently interacting with the system and their login times.
The useradd command, listed as option B, is used to add new users to the system. It is not related to displaying the list of logged-in users but is used by system administrators to create new accounts.
The w command, option C, displays information about the users currently logged in as well, but it also shows additional details such as the processes they are running, their idle time, and how long they’ve been logged in. While w is more detailed than who, both commands can be used to view the list of logged-in users.
The users command, option D, simply displays a list of usernames of all users currently logged in. It does not show any additional information, such as login time or terminal.
Therefore, the correct command for displaying a list of all users currently logged into the system is who. It provides a straightforward and essential view of the users who are currently interacting with the Linux system.