XK0-005 Practice Exam Questions with Answers CompTIA Linux+ Exam Certification

The main objective when using Application Control is to ensure the security and privacy of information. Application Control is a security practice that blocks or restricts unauthorized applications from executing in ways that put data at risk. The control functions vary based on the business purpose of the specific application, but the main objective is to help ensure the privacy and security of data used by and transmitted between applications1. Application Control can also prevent malware, untrusted, or unwanted applications from running on the network, reducing the risks and costs associated with data breaches1. Application Control can also improve the overall network stability and performance by eliminating unnecessary or harmful applications1.

Application Control is not mainly used to filter out specific content, although it can be combined with other technologies such as URL filtering or content filtering to achieve that goal. Application Control is not mainly used to assist the firewall blade with handling traffic, although it can be integrated with firewall policies to enforce granular access rules based on applications. Application Control is not mainly used to see what users are doing, although it can provide visibility and reporting on application usage and activity.

The ping command is used to measure network latency. The function provided uses ping -c 1 to ping the target once and extracts the average round-trip time using awk. This is a simple and effective way to monitor network latency during a scan or other network activity.

The yum history undo last command allows the administrator to undo the most recent transaction, effectively removing the httpd package and any installed dependencies. This is the safest and easiest way to revert package installations in RPM-based systems using yum.

The sshd is the Secure Shell Daemon, which is a service that allows remote login to a Linux system using the SSH protocol. The output shows that the sshd is running on port 2222, which is a non-standard port for SSH. The default port for SSH is 22, which is what the user is trying to use. Therefore, the statement B is most likely causing the issue. The statements A, C, and D are incorrect because they do not explain why the user cannot log on using port 22. References: [How to Change SSH Port in Linux]

To terminate an unresponsive process immediately without waiting for a graceful shutdown, the administrator can use the command kill -SIGKILL 5545 (A). This will send a signal to the process with the PID 5545 that cannot be ignored or handled by the process, and force it to stop. The other commands will send different signals that may allow the process to perform some cleanup or termination actions, or may be ignored by the process. References:

[CompTIA Linux+ Study Guide], Chapter 6: Managing Processes, Section: Killing Processes

[How to Kill Processes in Linux]

docker ps shows only running containers.

docker ps -a includes both running and stopped containers.

Incorrect Options:

B: Lists container images, not containers.

C: Shows resource usage of running containers.

D: Invalid syntax.

The systemctl reload httpd command reloads the Apache HTTP server configuration without terminating any existing connections. This is ideal for applying configuration changes without disrupting the current web traffic, ensuring seamless operation.

Tab 1: List of logins on Mar 13

Best Command:

grep "Mar 13" log.txt

Reasoning:

This command searches for lines in log.txt containing "Mar 13", which matches the date shown in the output. The result shows all login records for that day.

Tab 2: List of logins on Mar 12 (UPPERCASE) including REBOOT entries

Best Command:

awk '{ print toupper($0) }' log.txt

Reasoning:

All lines in the output are in UPPERCASE, including the word "REBOOT". This command converts every character in each line to uppercase, which matches the output format exactly.

Tab 3: List of unique usernames (sorted) including 'reboot'

Best Command:

awk '{ print $1 }' log.txt | sort | uniq

Reasoning:

This command extracts the first column (the username), sorts them, and removes duplicates, resulting in a list of unique usernames in alphabetical order. The output matches exactly.

? Tab 1 shows logins for "Mon Mar 13" –> grep "Mar 13" log.txt

? Tab 2 shows all entries in uppercase (including "REBOOT") for "Sun Mar 12" –> awk '{ print toupper($0) }' log.txt

? Tab 3 shows unique usernames in sorted order –> awk '{ print $1 }' log.txt | sort | uniq

? grep "Mar 13" log.txt

Searches for and displays all log entries from March 13.

? awk '{ print toupper($0) }' log.txt

Prints each line from log.txt in all uppercase letters (including system reboots).

? awk '{ print $1 }' log.txt | sort | uniq

Extracts just the username from each log entry, sorts them, and removes duplicates for a clean list.

The /etc/sudoers file is used to configure the sudo command, which allows non-privileged users to execute commands that require elevated account permissions1. The file contains a list of users and groups that are allowed to use sudo, and the commands they can run with it. The file also defines the security policy for sudo, such as whether a password is required, how long the sudo session lasts, and what environment variables are preserved or reset.

The /etc/passwd file is used to store information about the user accounts on the system, such as their username, user ID, home directory, and login shell. The /etc/shadow file is used to store the encrypted passwords for the user accounts, along with other information such as password expiration and aging. These files are not directly related to the sudo command, and updating them will not grant a user elevated account permissions.

The /etc/bashrc file is used to set up the environment for the bash shell, such as aliases, functions, variables, and options. This file is executed whenever a new bash shell is started, and it affects all users on the system. However, this file does not control the sudo command or its configuration, and updating it will not allow a user to use commands that require elevated account permissions.

The httpd.service is the Apache HTTPD Server, which is a web service that runs on Linux systems. The output 1 shows that the httpd.service is inactive (dead), which means that it is not running. The output 1 also shows that the httpd.service is disabled, which means that it is not enabled to auto start at boot time. Therefore, the statements C and D best describe the root cause of the issue. The statements A, B, E, and F are incorrect because they do not match the output 1. References: [How to Manage Systemd Services on a Linux System]

The error indicates corrupted kernel/initrd files.

Booting via rescue media (D) allows recovery without data loss.

Once in rescue, the administrator can reinstall kernel packages (E) to restore /boot.

Single-user mode (C) won’t work unless the kernel loads.

Replacing hardware or reinstalling the OS (A, F) is excessive and unnecessary.

Swap (B) is unrelated to kernel boot issues.

Production web servers should use certificates issued by trusted Certificate Authorities (CAs).

B is correct: This describes the proper process—generate a private key, create a CSR (Certificate Signing Request), send it to a CA, and use the returned signed certificate for HTTPS.

Incorrect Options:

A: SSH keys are for SSH, not HTTPS/TLS.

C: Self-signed certs are insecure in production.

D: Irrelevant to HTTPS; /dev/random is used for entropy generation.

The command that would address the memory-related issue is kill -9 8321. This command will send a SIGKILL signal to the process with the PID 8321, which is the mysqld process that is using 99.7% of the available memory according to the top output. The SIGKILL signal will terminate the process immediately and free up the memory it was using. However, this command should be used with caution as it may cause data loss or corruption if the process was performing some critical operations.

The other options are not correct commands for addressing the memory-related issue. The top -p 8321 command will only display information about the process with the PID 8321, but will not kill it or reduce its memory usage. The renice -10 8321 command will change the priority (niceness) of the process with the PID 8321 to -10, which means it will have a higher scheduling priority, but this will not affect its memory consumption. The free 8321 command is invalid because free does not take a PID as an argument; free only displays information about the total, used, and free memory in the system. References: How to troubleshoot Linux server memory issues; kill(1) - Linux manual page

The command systemct1 status systemd-resolved.service will show the information about the service systemd-resolved.service. The systemct1 command is a tool for managing system services and units. The status option displays the current status of a unit, such as active, inactive, or failed. The output also shows the unit description, loaded configuration, process ID, memory usage, and recent log messages. This command will show if the service systemd-resolved.service is running without any errors. This is the correct command to use to accomplish the task. The other options are incorrect because they either perform different actions (enable, mask, or show) or do not show the status of the service (systemct1 show systemd-resolved.service only shows the properties of the service, not the status). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 14: Managing Processes and Scheduling Tasks, page 427.

The command that will accomplish this task is sudo useradd -e 2021-09-30 Project_user. This command will create a new user account named Project_user with an expiration date of 2021-09-30. The -e option of useradd specifies the date on which the user account will be disabled in YYYY-MM-DD format.

The other options are not correct commands for creating a user account with an expiration date. The sudo useradd -c 2021-09-30 Project_user command will create a new user account named Project_user with a comment of 2021-09-30. The -c option of useradd specifies a comment or description for the user account, not an expiration date. The sudo modinfo -F 2021-09-30 Project_user command is invalid because modinfo is not a command for managing user accounts, but a command for displaying information about kernel modules. The -F option of modinfo specifies a field name to show, not an expiration date. The sudo useradd -m -d 2021-09-30 Project_user command will create a new user account named Project_user with a home directory of 2021-09-30. The -m option of useradd specifies that the home directory should be created if it does not exist, and the -d option specifies the home directory name, not an expiration date. References: useradd(8) - Linux manual page; modinfo(8) - Linux manual page

The command that will accomplish the goal of avoiding the deletion or modification of files from non-owners is chmod +t /project/access2all. This command will set the sticky bit on the directory /project/access2all, which is a special permission that restricts file deletion or renaming to only the file owner, directory owner, or root user. This way, even if multiple users have write permission to the directory, they cannot delete or modify each other’s files.

The other options are not correct commands for accomplishing the goal. The chmod +rws /project/access2all command will set both the SUID and SGID bits on the directory, which are special permissions that allow a program or a directory to run or be accessed with the permissions of its owner or group, respectively. However, this does not prevent file deletion or modification from non-owners. The chmod 2770 /project/access2all command will set only the SGID bit on the directory, which means that any new files or subdirectories created in it will inherit its group ownership. However, this does not prevent file deletion or modification from non-owners. The chmod ugo+rwx /project/access2all command will grant read, write, and execute permissions to all users (user, group, and others) on the directory, which means that anyone can delete or modify any file in it. References: chmod(1) - Linux manual page; How to Use SUID, SGID, and Sticky Bits on Linux

The most likely issue is that the service does not have permissions to read or write the startupfile. The output of systemct1 status startup.service shows that the service has failed to start and the error message is “Permission denied”. The output of ls -l /etc/startupfile shows that the file has the permissions -rw-r--r--, which means that only the owner (root) can read and write the file, while the group (root) and others can only read the file. The service may not run as root and may need write access to the file. The administrator should change the permissions of the file by using the chmod command and grant write access to the group or others, or change the owner or group of the file by using the chown command and assign it to the user or group that runs the service. The other options are incorrect because they are not supported by the outputs. The file size, owner, and group are not the causes of the issue. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing Files and Directories, pages 345-346.

The command that would resolve the issue is chmod 600 .ssh/authorized_keys. This command will change the permissions of the .ssh/authorized_keys file to 600, which means that only the owner of the file can read and write it. This is necessary for SSH key authentication to work properly, as SSH will refuse to use a key file that is accessible by other users or groups for security reasons. The output of ls -l shows that currently the .ssh/authorized_keys file has permissions of 664, which means that both the owner and group can read and write it, and others can read it.

The other options are not correct commands for resolving the issue. The restorecon .ssh/authorized_keys command will restore the default SELinux security context for the .ssh/authorized_keys file, but this will not change its permissions or ownership. The ssh_keygen -t rsa -o .ssh/authorized_keys command is invalid because ssh_keygen is not a valid command (the correct command is ssh-keygen), and the -o option is used to specify a new output format for the key file, not the output file name. The chown root:root .ssh/authorized_keys command will change the owner and group of the .ssh/authorized_keys file to root, but this will not change its permissions or make it accessible by the user who wants to log in with SSH key authentication. References: How to Use Public Key Authentication with SSH; chmod(1) - Linux manual page

The docker logs command retrieves logs, including errors, for a running container. By using docker logs WEB, the administrator can check the error output generated by the web server container and debug any issues related to application performance or errors.

To enable root login over SSH, the administrator must edit the /etc/ssh/sshd_config file, which configures the SSH daemon. The PermitRootLogin directive should be set to yes to allow root login. After making this change, the SSH daemon must be restarted for the changes to take effect.

A function of a bootloader is to help load the different kernels to initiate the OS startup process. A bootloader is a program that runs when the system is powered on and prepares the system for booting the OS. A bootloader can load different kernels, which are the core components of the OS, and pass the control to the selected kernel. A bootloader can also provide a menu for the user to choose which kernel or OS to boot. This is a correct function of a bootloader. The other options are incorrect because they are either functions of the kernel (initialize devices or mount root filesystem) or functions of the init system (trigger the start of system services). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 8: Managing the Linux Boot Process, page 265.

The output from free -m shows that a significant portion of the swap space (955 MB) is being used, indicating the server is swapping. Swapping occurs when the system runs low on physical memory, leading to poor performance because the system must offload memory pages to the slower swap space. To resolve this, either more physical memory should be added or the application’s memory usage should be optimized.

The command chattr +a /opt/app/logs will ensure the log file can only be written into without removing previous entries. The chattr command is a tool for changing file attributes on Linux file systems. The +a option sets the append-only attribute, which means that the file can only be opened in append mode for writing. This prevents the file from being modified, deleted, or renamed. This is the best command to use to accomplish the task. The other options are incorrect because they either set the wrong attributes (+d, +i, or +c) or do not affect the file at all (-a). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing Files and Directories, page 357.

The command that will satisfy the requirement of having all files that are created by the user named web have read-only permissions by the owner is echo “umask 377” >> /home/web/.bashrc. This command will append the umask 377 command to the end of the .bashrc file in the web user’s home directory. The .bashrc file is a shell script that is executed whenever a new interactive shell session is started by the user. The umask command sets the file mode creation mask, which determines the default permissions for newly created files or directories by subtracting from the maximum permissions (666 for files and 777 for directories). The umask 377 command means that the user does not want to give any permissions to the group or others (3 = 000 in binary), and only wants to give read permission to the owner (7 - 3 = 4 = 100 in binary). Therefore, any new file created by the web user will have read-only permission by the owner (400) and no permission for anyone else. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 8: Managing Users and Groups; Umask Command in Linux | Linuxize

The reason the firewall rules are not active is that the firewalld service is not enabled. This means that the service will not start automatically at boot time or after a system reload. To enable the firewalld service, the systems administrator needs to use the command sudo systemct1 enable firewalld. This will create a symbolic link from the firewalld service file to the appropriate systemd target, such as multi-user.target. Enabling the service does not start it immediately, so the systems administrator also needs to use the command sudo systemct1 start firewalld or sudo systemct1 reload firewalld to activate the firewall rules.

The other options are not correct reasons for the firewall rules not being active. iptables is not conflicting with firewalld, because firewalld uses iptables as its backend by default. The wrong system target is not activated, because firewalld is independent of the system target and can be enabled for any target. FIREWALL_ARGS has no value assigned, but this is not a problem, because FIREWALL_ARGS is an optional environment variable that can be used to pass additional arguments to the firewalld daemon, such as --debug or --nofork. If FIREWALL_ARGS is empty or not defined, firewalld will use its default arguments. References: firewalld.service(8) - Linux manual page; firewall-cmd(1) - Linux manual page; systemct1(1) - Linux manual page

The commands that can be used together to persistently enable IPv4 forwarding in one of the Linux systems are sysctl -w net.ipv4.ip_forward=1 and sysctl –p. The first command will use sysctl to write a new value (1) to the net.ipv4.ip_forward kernel parameter, which controls whether IP forwarding is enabled or disabled for IPv4. This will enable IP forwarding immediately without rebooting. However, this change is temporary and will be lost after a reboot or a system reload. To make it permanent, we need to use the second command sysctl –p, which will load kernel parameters from /etc/sysctl.conf file. This file contains key-value pairs of kernel parameters and their values. To make sure that net.ipv4.ip_forward is set to 1 in this file, we can either edit it manually or append it using echo “net.ipv4.ip_forward=1” >> /etc/sysctl.conf.

The other options are not correct commands for persistently enabling IPv4 forwarding. The sysctl net.ipv4.ip_forward command will only display the current value of net.ipv4.ip_forward parameter, but not change it. The echo 1 > /proc/sys/net/ipv4/ip_forward command will write 1 to /proc/sys/net/ipv4/ip_forward file, which is another way to change net.ipv4.ip_forward parameter. However, this change is also temporary and will not survive a reboot or a system reload. The echo “net.ipv6.conf.all.forwarding=l” >> /etc/sysctl.conf command will append a line to /etc/sysctl.conf file that sets net.ipv6.conf.all.forwarding parameter to 1. However, this parameter controls whether IP forwarding is enabled or disabled for IPv6, not IPv4. References: sysctl(8) - Linux manual page; Configure Linux as a Router (IP Forwarding)

This answer allows the accounting user to run the /opt/acc/report command as root on any host without entering a password. The % sign indicates that accounting is a group name, not a user name. The ALL keyword means any host, any user, and any command, depending on the context. The NOPASSWD tag overrides the default behavior of sudo, which is to ask for the user’s password.

The other answers are incorrect for the following reasons:

A. accounting localhost=/opt/acc/report

This answer only allows the accounting user to run the command on the localhost, not on any host.

This answer also requires the accounting user to enter their password, which is not specified in the question.

B. accounting ALL=/opt/acc/report

This answer only allows the accounting user to run the command as themselves, not as root.

This answer also requires the accounting user to enter their password, which is not specified in the question.

D. accounting /opt/acc/report= (ALL) NOPASSWD: ALL

This answer has an invalid syntax, as there should be no space between the equal sign and the parentheses.

This answer also grants too much privilege to the accounting user, as it allows them to run any command as any user without a password.

The git fetch command downloads commits, files, and refs from a remote repository into the local one. It also updates the remote-tracking branches, which are references to the state of the remote branches. By running git fetch, the administrator can see the new branch created by the development team and then use git checkout to switch to it12.

The command setfacl -m g:finance:rw file will permanently fix the access issue while limiting access to IT and finance department employees. The setfacl command is a tool for modifying the access control lists (ACLs) of files and directories on Linux systems. The ACLs are a mechanism that allows more fine-grained control over the permissions of files and directories than the traditional owner-group-others model. The -m option specifies the modification to the ACL. The g:finance:rw means that the group named finance will have read and write permissions on the file. The file is the name of the file to modify, in this case /opt/work/file. The command setfacl -m g:finance:rw file will add an entry to the ACL of the file that will grant read and write access to the finance group. This will fix the access issue and allow the finance employees to access the file. The command will also preserve the existing permissions of the file, which means that the IT employees will still have read and write access to the file. This will limit the access to IT and finance department employees and prevent unauthorized access from other users. This is the correct command to use to accomplish the task. The other options are incorrect because they either do not fix the access issue (chattr +i file or chown it:finance file) or do not limit the access to IT and finance department employees (chmod 666 file). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing File Permissions and Ownership, page 352.

If the application server can ping the database server by its IP address but not by its hostname, it indicates a DNS resolution issue. The most likely cause is incorrect DNS server configuration. The engineer should verify the DNS settings in /etc/resolv.conf or the network configuration.

The IP ping works, but DNS resolution fails, indicating that a DNS server is not configured properly in /etc/resolv.conf. That file is responsible for DNS resolution.

Source: CompTIA Linux+ XK0-005 Study Guide – Chapter 9: Networking

The best tool to use when uploading the public key to the remote servers is B. ssh-copy-id. This tool will copy the public key from the local computer to the remote server and append it to the authorized_keys file, which is used for public key authentication. This tool will also create the necessary directories and files on the remote server if they do not exist. The other tools are either not suitable or not relevant for this task. For example:

A. scp is a tool for securely copying files between hosts, but it does not automatically add the public key to the authorized_keys file.

C. ssh-agent is a tool for managing private keys and passphrases, but it does not upload the public key to the remote server.

D. ssh-keyscan is a tool for collecting public keys from remote hosts, but it does not upload the public key to the remote server.

YAML (YAML Ain't Markup Language) is a human-readable data serialization format often used for configuration files and in Infrastructure as Code (IaC) tools such as Ansible and Kubernetes. YAML files are easy to read and write, making them ideal for specifying infrastructure configurations and managing declarative environments.

TRIM is a feature that allows the operating system to inform the SSD which blocks of data are no longer in use and can be wiped internally. This helps to maintain the SSD’s performance and endurance by preventing unnecessary write operations and reducing write amplification12. Running the corresponding command to trim the SSD drives, such as fstrim or blkdiscard on Linux, can help to solve the issue of slow writes by freeing up space and optimizing the SSD’s internal garbage collection34.

The chage command can be used to change the user password expiry information. The -d or --lastday option sets the last password change date. If the value is 0, the user will be forced to change the password at the next login. See chage command in Linux with examples and 10 chage command examples in Linux.

The lsscsi command can list the SCSI devices on the system, along with their size and device name. The -s option shows the size of each device. The administrator can look for the device that has a size of 500G and note its device name. See lsscsi(8) - Linux man page and How to check Disk Interface Types in Linux.References1: https://linux.die.net/man/8/lsscsi2: https://www.golinuxcloud.com/check-disk-type-linux/

An administrator accidentally installed the httpd RPM package along with several dependencies. Which of the following options is the best way for the administrator to revert the package

installation?

dnf clean all

rpm -e httpd

apt-get clean

yum history undo last

Answer: D

The yum history undo last command will undo the last transaction, which in this case is the installation of the httpd RPM package and its dependencies. This will remove the packages that were installed and restore the previous state of the system. See How to undo or redo yum transactions and yum history.References1: https://www.redhat.com/sysadmin/undo-redo-yum-transactions2: https://man7.org/linux/man-pages/man8/yum.8.html#HISTORY

JSON is widely used in APIs and automation tools due to its structured format and broad language support.

YAML is designed to be more human-readable and concise, used often in Ansible, Kubernetes, and other configuration scenarios.

Option B best captures this distinction.

Comprehensive and Detailed Explanation From Exact Extract:

wc -l counts the number of lines of input provided to it, which is commonly used to count the number of files when used with ls -l (excluding the header line). For example, ls -l /opt/application/home/ | wc -l gives the total count of lines, which corresponds to the number of files and directories (including the total line at the top).

Other options:

A. less is a pager utility.

B. tail -f shows the end of a file in real time.

C. tr -c translates or deletes characters, not for counting lines.

The docker run -d --name web-01 httpd command will launch a container named web-01 in background mode. This command will create and start a new container from the httpd image, assign it the name web-01, and run it in detached mode (-d), which means the container will run in the background without attaching to the current terminal. The docker builder -f --name web-01 httpd command is invalid, as builder is not a valid docker command, and -f and --name are not valid options for docker build. The docker load --name web-01 httpd command is invalid, as load does not accept a --name option, and httpd is not a valid file name for load. The docker ps -a --name web-01 httpd command is invalid, as ps does not accept a --name option, and httpd is not a valid filter for ps. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 16: Virtualization and Cloud Technologies, page 499.

The command ip route get 192.168.1.40 from 10.0.2.15 will test the route between the IP address 10.0.2.15 and the IP address 192.168.1.40. The ip route get command shows the routing decision for a given destination and source address. This is the correct command to accomplish the task. The other options are incorrect because they either use the wrong commands (route instead of ip route), the wrong options (-e or -n instead of get), or the wrong syntax (to instead of from). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 12: Managing Network Connections, page 379.

w shows currently logged-in users and their processes.

man shows manual pages.

id shows UID/GID for current user.

host is a DNS lookup tool.

After fixing issues in the code, the next step is to merge these changes into the main branch. This is typically done by creating a pull request78.

The command that will back up the directory /data and all its contents to /backup/data on a remote server named remote is rsync -a /data remote:/backup/. This command uses the rsync tool, which is a remote and local file synchronization tool. It uses an algorithm to minimize the amount of data copied by only moving the portions of files that have changed. The -a option stands for archive mode, which preserves the permissions, ownership, timestamps, and symbolic links of the files. The /data argument specifies the source directory to be backed up, and the remote:/backup/ argument specifies the destination directory on the remote server. The rsync tool will create a subdirectory named data under /backup/ on the remote server, and copy all the files and subdirectories from /data on the local server.

The other options are not correct commands for backing up a directory to a remote server. The scp -p /data remote:/backup/data command will copy the /data directory as a file named data under /backup/ on the remote server, not as a subdirectory with its contents. The -p option preserves the permissions and timestamps of the file, but not the ownership or symbolic links. The ssh -i /remote:/backup/ /data command will try to use /remote:/backup/ as an identity file for SSH authentication, which is not valid. The cp -r /data /remote/backup/ command will try to copy the /data directory to a local directory named /remote/backup/, not to a remote server. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 18: Automating Tasks; rsync(1) - Linux manual page

The command cat toDelete.txt | xargs rm -rf will delete all files and directories with names that are contained in the toDelete.txt file. The cat command reads the file and outputs its contents to the standard output. The | operator pipes the output to the next command. The xargs command converts the output into arguments for the next command. The rm -rf command removes the files and directories recursively and forcefully. This is the correct way to accomplish the task. The other options are incorrect because they either use the wrong options (-f instead of -a for xargs), the wrong arguments (toDelete.txt instead of toDelete.txt filename for rm), or the wrong commands (rm instead of xargs). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing Files and Directories, pages 349-350.

The commands that will list and remove the corresponding packages are dnf history and dnf history undo last. The dnf history command will display a list of all transactions performed by dnf, such as installing, updating, or removing packages. Each transaction has a unique ID, a date and time, an action, and a number of altered packages. The dnf history undo last command will undo the last transaction performed by dnf, meaning that it will reverse all package changes made by that transaction. For example, if the last transaction installed some packages, dnf history undo last will remove them.

The other options are not correct commands for listing and removing corresponding packages. The dnf list command will display a list of available packages in enabled repositories, but not the packages installed by dnf transactions. The dnf remove command will remove specified packages from the system, but not all packages from a specific transaction. The dnf info command will display detailed information about specified packages, but not about dnf transactions. The dnf upgrade command will upgrade all installed packages to their latest versions, but not undo any package changes. References: Handling package management history; dnf(8) - Linux manual page

For normal users to change their own password, /bin/passwd must have the SUID bit set (permissions should be -rwsr-xr-x). The SUID bit allows users to run the program with the permissions of the file owner (root), which is required to update /etc/shadow. The provided output shows /bin/passwd does not have the SUID bit (no 's' in the owner’s execute field). As a result, user "test" receives an "Authentication token manipulation error". The password can be changed as root, which confirms it's a permissions/SUID issue.

Other options:

B. If the password didn’t meet requirements, a different error would appear.

C. There is no minimum day limit preventing password change (see chage -l output).

D. The account and password are active (not disabled).

The command iptables -t nat -A PREROUTING -p tcp --dport 80 -j DNAT --to-destination 192.0.2.25:3128 adds a rule to the nat table that redirects all incoming TCP packets with destination port 80 (HTTP) to the proxy server 192.0.2.25 on port 3128. This is the correct way to achieve the task. The other options are incorrect because they either delete a rule (-D), use the wrong protocol (top instead of tcp), or use the wrong port (81 instead of 80). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 12: Managing Network Connections, page 381.

The command pam_tally2 -u joe -r will resolve the issue of Joe being unable to log in to the Linux system. The pam_tally2 command is a tool for managing the login counter for the PAM (Pluggable Authentication Modules) system. PAM is a framework for managing authentication and authorization on Linux systems. PAM allows the administrator to define the rules and policies for accessing various system resources and services, such as login, sudo, ssh, or cron. PAM also supports different types of authentication methods, such as passwords, tokens, biometrics, or smart cards. PAM can be used to implement login restrictions, such as limiting the number of failed login attempts, locking the account after a certain number of failures, or enforcing a minimum or maximum time between login attempts. The pam_tally2 command can display, reset, or unlock the login counter for the users or hosts. The -u joe option specifies the user name that the command should apply to. The -r option resets the login counter for the user. The command pam_tally2 -u joe -r will reset the login counter for Joe, which will unlock his account and allow him to log in to the Linux system. This will resolve the issue of Joe being unable to log in to the Linux system. This is the correct command to use to resolve the issue. The other options are incorrect because they either do not unlock the account (usermod -s /bin/bash joe or passwd -u joe) or do not affect the login counter (chage -E 90 joe). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 17: Implementing Basic Security, page 517.

The command ls | cpio -ov > cloud.cpio can help to create a new cloud.cpio archive containing all the files from the current directory. The ls command lists the files in the current directory and outputs them to the standard output. The | operator pipes the output to the next command. The cpio command is a tool for creating and extracting compressed archives. The -o option creates a new archive and the -v option shows the verbose output. The > operator redirects the output to the cloud.cpio file. This command will create a new cloud.cpio archive with all the files from the current directory. The other options are incorrect because they either use the wrong options (-i instead of -o), the wrong arguments (cloud.epio instead of cloud.cpio), or the wrong syntax (< instead of > or missing |). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing Files and Directories, page 351.

The PAM module pam_nologin.so will prevent logins from accounts other than root, while the file /etc/nologin exists. This module checks for the existence of the file /etc/nologin and displays its contents to the user before denying access. The root user is exempt from this check and can still log in. This is the correct module to accomplish the task. The other options are incorrect because they are either non-existent modules (pam_login.so or pam_logindef.so) or do not perform the required function (pam_access.so controls access based on host, user, or time). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 15: Managing Users and Groups, page 471.

The correct command to list all local accounts in which the UID is greater than 500 is:

awk -F: '$3 > 500 {print $1}' /etc/passwd

This command uses awk to process the /etc/passwd file, which contains information about the local users on the system. The -F: option specifies that the fields are separated by colons. The $3 refers to the third field, which is the UID. The condition $3 > 500 filters out the users whose UID is greater than 500. The action {print $1} prints the first field, which is the username.

The other commands are incorrect because:

find /etc/passwd —size +500 will search for files that are larger than 500 blocks in size, not users with UID greater than 500.

cut —d: fl / etc/ passwd > 500 will cut the first field of the /etc/passwd file using colon as the delimiter, but it will not filter by UID or print only the usernames. The > 500 part will redirect the output to a file named 500, not compare with the UID.

sed '/UID/' /etc/passwd < 500 will use sed to edit the /etc/passwd file and replace any line that contains UID with 500, not list the users with UID greater than 500. The < 500 part will redirect the input from a file named 500, not compare with the UID.

Based on the output of the image sent by the user, the system requires more swap space to allow for spikes in usage during peak hours and prevent the Java process from stopping due to a lack of memory. The output shows that there is only 0 MB of swap space available on the system, which means that there is no room for swapping out memory pages when physical memory is full or low. The output also shows that there is only 793 MB of available memory on the system, which may not be enough to handle high-demand applications such as Java. This may cause Java to stop working due to insufficient memory or trigger an OutOfMemoryError exception. Configuring more swap space on the system would help to alleviate this issue by providing more virtual memory for applications and improving performance. Configuring memory allocation policies during business hours will not help to solve this issue, as it will not increase the amount of available memory or swap space on the system. Configuring a different nice value for Java process will not help to solve this issue, as it will only affect its scheduling priority, not its memory consumption or allocation. Configuring more CPU cores will not help to solve this issue, as it will only increase processing power, not memory capacity or availability. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 15: Managing Memory and Process Execution, page 468.

The ip link show eth1 command can be used to check the link status of a network interface named eth1 in a Linux server. It will display information such as the MAC address, MTU, state, and flags of the interface. The ifconfig hw eth1 command is invalid, as hw is not a valid option for ifconfig. The netstat -r eth1 command would display the routing table for eth1, not the link status. The ss -ti eth1 command would display TCP information for sockets associated with eth1, not the link status. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 13: Networking Fundamentals, page 436.

The OnCalendar schedule is incorrect in the timer definition, which is causing the issue. The OnCalendar schedule defines when the timer should trigger the service. The format of the schedule is OnCalendar=-- ::. If any of the fields are omitted, they are assumed to be *, which means any value. Therefore, the schedule OnCalendar=*-*-* 00:00:00 means every day at midnight, which is why the job is running daily. To make the job run every two hours, the schedule should be OnCalendar=*-*-* *:00:00/2, which means every hour divisible by 2 at the start of the minute. The other options are incorrect because they are not related to the schedule. The checkdiskspace.service is running, as shown by the output of systemct1 status checkdiskspace.service. The checkdiskspace.service is enabled, as shown by the output of systemct1 is-enabled checkdiskspace.service. The system-daemon services do not need to be reloaded, as the timer and service definitions are already loaded by the restart. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 14: Managing Processes and Scheduling Tasks, page 437.

The issue occurs because the home directory /home/userA is owned by root, not by userA, as seen from the ls -lth /home output. In Linux, the user must have ownership of their home directory to log in and access their files properly. To fix this, the administrator must change ownership using chown userA:userA /home/userA.

The administrator can use the following two options to boot the system into the single user mode:

Interrupt the boot process in the GRUB menu and add systemd.unit=rescue.target in the kernel line. This option will boot the system into the rescue mode, which is a minimal environment that allows the administrator to perform basic tasks such as repairing the system. The GRUB menu is a screen that appears when the system is powered on and allows the administrator to choose which kernel or operating system to boot. The kernel line is a line that specifies the parameters for the kernel, such as the root device, the init system, and the boot options. The administrator can interrupt the boot process by pressing the e key in the GRUB menu and edit the kernel line by adding systemd.unit=rescue.target at the end. This option will tell the system to use the rescue target, which is a unit that defines the state of the system in the rescue mode. The administrator can then press Ctrl+X to boot the system with the modified kernel line. This option will boot the system into the single user mode and allow the administrator to troubleshoot the issues.

Interrupt the boot process in the GRUB menu and add systemd.unit=single.target in the kernel line. This option will boot the system into the single user mode, which is a mode that allows the administrator to log in as the root user and perform maintenance tasks. The GRUB menu and the kernel line are the same as the previous option. The administrator can interrupt the boot process by pressing the e key in the GRUB menu and edit the kernel line by adding systemd.unit=single.target at the end. This option will tell the system to use the single target, which is a unit that defines the state of the system in the single user mode. The administrator can then press Ctrl+X to boot the system with the modified kernel line. This option will boot the system into the single user mode and allow the administrator to troubleshoot the issues.

The other options are incorrect because they either do not boot the system into the single user mode (execute the following command from the GRUB rescue shell: mount -o remount, ro/sysroot or interrupt the boot process in the GRUB menu and add systemd.unit=single in the kernel line) or do not use the correct syntax (interrupt the boot process in the GRUB menu and add single=user in the kernel line or interrupt the boot process in the GRUB menu and add init=/bin/bash in the kernel line). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 8: Managing the Linux Boot Process, pages 267-268.

The correct sequence of commands to expand a volume group using a new disk is fdisk, pvcreate, vgextend. The fdisk command can be used to create a partition on the new disk with the type 8e (Linux LVM). The pvcreate command can be used to initialize the partition as a physical volume for LVM. The vgextend command can be used to add the physical volume to an existing volume group. The partprobe command can be used to inform the kernel about partition table changes, but it is not necessary in this case. The vgcreate command can be used to create a new volume group, not expand an existing one. The lvextend command can be used to extend a logical volume, not a volume group. The lvcreate command can be used to create a new logical volume, not expand a volume group. The mkfs command can be used to create a filesystem on a partition or a logical volume, not expand a volume group. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 14: Managing Disk Storage, pages 462-463.

The commands ssh-copy-id and scp can be used to copy a key file to remote servers. The command ssh-copy-id copies the public key to the authorized_keys file on the remote server, which allows the user to log in without a password. The command scp copies files securely over SSH, which can be used to transfer the key file to any location on the remote server. The other options are incorrect because they are not related to copying key files. The command wget downloads files from the web, the command ssh-keygen generates key pairs, the command ssh-keyscan collects public keys from remote hosts, and the command ftpd is a FTP server daemon. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 13: Managing Network Services, pages 408-410.

Terraform is a tool for building, changing, and managing infrastructure as code in a cloud-based environment. Terraform uses configuration files to describe the desired state of the infrastructure and applies changes accordingly. Terraform supports various cloud providers, such as AWS, Azure, Google Cloud Platform, and more.

To validate changes before they are applied to the cloud-based environment, the administrator can use the terraform plan command. This command will compare the current state of the infrastructure with the desired state defined in the configuration files and show what actions will be performed to achieve the desired state. This command will not make any changes to the infrastructure but only show a plan of changes. The statement D is correct.

The statements A, B, and C are incorrect because they do not validate changes before they are applied to the cloud-based environment. Ansible is another tool for automating infrastructure management, but it does not have a plan command. Git clone and git pull are commands for working with git repositories, which are used for version control of code. References: [How to Use Terraform to Manage Cloud Infrastructure]

The administrator should do the following two actions to resolve the issue:

Boot the system on a LiveCD/ISO. This is necessary to access the system and repair the boot loader. A LiveCD/ISO is a bootable media that contains a Linux distribution that can run without installation. The administrator can boot the system from the LiveCD/ISO and mount the root partition of the system to a temporary directory, such as /mnt.

Execute grub-install /dev/sdX and reboot. This will reinstall the GRUB boot loader to the disk device, where sdX is the device name of the disk, such as sda or sdb. The GRUB boot loader is a program that runs when the system is powered on and allows the user to choose which operating system or kernel to boot. The issue is caused by a corrupted or missing GRUB boot loader, which prevents the system from booting. The command grub-install will restore the GRUB boot loader and fix the issue.

The other options are incorrect because they either do not fix the boot loader (interrupt the boot process in the GRUB menu or fix the partition modifying /etc/default/grub) or do not use the correct syntax (grub-install --root-directory=/mnt instead of grub-install /dev/sdX or rescue or single instead of recovery in the GRUB menu). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 8: Managing the Linux Boot Process, pages 265-266.

The command semanage port -a -t http_port_t -p tcp 6379 adds a new port definition to the SELinux policy and assigns the type http_port_t to the port 6379/tcp. This allows the web application to run on this port and accept connections from users. This is the correct way to resolve the issue. The other options are incorrect because they either delete a port definition (-d), use the wrong protocol (top instead of tcp), or list the existing port definitions (-l). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 18: Securing Linux Systems, page 535.

The command chage -E -1 accountname will accomplish the task of removing the expiration date of a user account. The chage command is a tool for changing user password aging information on Linux systems. The -E option sets the expiration date of the user account, and the -1 value means that the account will never expire. The command chage -E -1 accountname will remove the expiration date of the user account named accountname. This is the correct command to use to accomplish the task. The other options are incorrect because they either do not affect the expiration date (chgrp, passwd, or chmod) or do not exist (chmod -G). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 15: Managing Users and Groups, page 467.

The command umask 002 will accomplish the task of reconfiguring the server so that only file owners and group members can modify new files by default. The umask command is a tool for setting the default permissions for new files and directories on Linux systems. The umask value is a four-digit octal number that represents the permissions that are subtracted from the default permissions. The default permissions for files are 666, which means read and write for owner, group, and others. The default permissions for directories are 777, which means read, write, and execute for owner, group, and others. The umask value consists of four digits: the first digit is for special permissions, such as setuid, setgid, and sticky bit; the second digit is for the owner permissions; the third digit is for the group permissions; and the fourth digit is for the others permissions. The umask value can be calculated by subtracting the desired permissions from the default permissions. For example, if the desired permissions for files are 664, which means read and write for owner and group, and read for others, then the umask value is 002, which is 666 - 664. The command umask 002 will set the umask value to 002, which will ensure that only file owners and group members can modify new files by default. This is the correct command to use to accomplish the task. The other options are incorrect because they either do not set the default permissions for new files (chmod 775 or chown -cf) or do not exist (chattr -Rv). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing File Permissions and Ownership, page 349.

The command docker cp container_id:/deployment.yaml deployment.yaml can accomplish the task of copying the file deployment.yaml from a container to the host. The docker command is a tool for managing Docker containers and images. The cp option copies files or directories between a container and the local filesystem. The container_id is the identifier of the container, which can be obtained by using the docker ps command. The /deployment.yaml is the path of the file in the container, which must be preceded by a slash. The deployment.yaml is the path of the file on the host, which can be relative or absolute. The command docker cp container_id:/deployment.yaml deployment.yaml will copy the file deployment.yaml from the container to the current working directory on the host. This is the correct command to use to accomplish the task. The other options are incorrect because they either use the wrong syntax (docker cp container_id/deployment.yaml deployment.yaml or docker cp container_id/deployment.yaml local://deployment.yaml) or do not exist (docker cp deployment.yaml local://deployment.yaml). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Cloud and Virtualization Technologies, page 567.

The server’s firewall is preventing connections from being made, which is causing the connectivity issue. The output of iptables -L -n shows that the firewall is blocking all incoming traffic on port 22, which is the default port for SSH. The output of ssh -v user@104.21.75.76 shows that the connection is refused by the server. To resolve the issue, the administrator needs to allow port 22 on the firewall. The other options are incorrect because they are not supported by the outputs. The workstation has the correct IP settings, as shown by the output of ip addr show. The sshd service is enabled and running, as shown by the output of systemct1 status sshd. The server has the correct default gateway configuration, as shown by the output of ip route show. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 13: Managing Network Services, pages 406-407.

The user has the wrong shell assigned to the account, which is causing the issue. The output 1 shows that the user’s shell is set to /bin/false, which is not a valid shell and will prevent the user from logging in. The output 2 shows that the user’s home directory has the correct permissions (drwxr-xr-x), and the output 3 shows that the user entered the correct password and was accepted by the SSH daemon, but the session was closed immediately due to the invalid shell. The other options are incorrect because they are not supported by the outputs. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 13: Managing Network Services, page 413.

The wget command is used to download files from remote servers via HTTP, HTTPS, and FTP.

Option D (Correct): wget retrieves files from a specified URL.

Option A (netstat): Used to display network connections, not for downloading files.

Option B (nc – Netcat): Used for networking and port scanning, not file downloads.

Option C (telnet): Used for remote terminal connections, not for downloading files.

The command useradd -d /comptia/projects user02 will accomplish the task of creating a new user named user02 with a different home directory. The useradd command is a tool for creating new user accounts on Linux systems. The -d option specifies the home directory for the new user, which is the directory where the user’s personal files and settings are stored. The /comptia/projects is the path of the home directory for the new user, which is different from the default location of /home/user02. The user02 is the name of the new user. The command useradd -d /comptia/projects user02 will create a new user named user02 with a home directory under /comptia/projects. This is the correct command to use to accomplish the task. The other options are incorrect because they either do not specify the home directory for the new user (useradd -m /comptia/projects user02 or useradd -s /comptia/projects user02) or do not use the correct option for the home directory (useradd -b /comptia/projects user02 instead of useradd -d /comptia/projects user02). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 13: Managing Users and Groups, page 403.

The required changes need to be made to the /etc/login.defs configuration file. The /etc/login.defs file defines the default values for user and group IDs, passwords, shells, and other parameters for user and group creation. The file contains the directives UID_MIN, UID_MAX, GID_MIN, and GID_MAX, which set the minimum and maximum values for automatic user and group ID selection. The administrator can edit this file and change the values to match the organization’s new cybersecurity policies. This is the correct file to modify to accomplish the task. The other options are incorrect because they either do not affect the user and group IDs (/etc/security/limits.conf or /etc/profile) or do not set the default values (/etc/default/useradd). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 15: Managing Users and Groups, page 463.

To set up passwordless SSH authentication, the public key from the client must be added to the ~/.ssh/authorized_keys file on the remote server.

Private keys must never be copied to another machine.

Option B is insecure; option C is unnecessary unless the remote server needs key-based login itself.

The command that the administrator should run to ensure that both Java 7 and Java 8 are locally available for developers to use when deploying containers is docker image pull java:7. This command will use the docker image pull subcommand to download the java:7 image from Docker Hub, which is the default registry for Docker images. The java:7 image contains Java 7 installed on a Debian-based Linux system. The administrator can also specify a different registry by using the syntax registry/repository:tag.

The other options are not correct commands for ensuring that both Java 7 and Java 8 are locally available for developers to use when deploying containers. The docker image load java:7 command will load an image from a tar archive or STDIN, not from a registry. The docker image import java:7 command will create a new filesystem image from the contents of a tarball, not from a registry. The docker image build java:7 command will build an image from a Dockerfile, not from a registry. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 18: Automating Tasks; docker image pull | Docker Docs

The command source ~/.bashrc should be executed first to use the alias command. The source command reads and executes commands from a file in the current shell environment. The ~/.bashrc file is a configuration file that contains commands and aliases that are executed when a new bash shell is started. The administrator made some changes in the ~/.bashrc file and added an alias command, but the changes are not effective until the file is sourced or a new shell is started. The command source ~/.bashrc will reload the file and make the alias command available. The other options are incorrect because they either do not execute the commands in the file (read, touch, or echo) or do not affect the current shell environment (read or echo). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 9: Working with the Linux Shell, page 295.

The administrator should use the command kill -TERM to forcibly stop the process. The kill command is a tool for sending signals to processes on Linux systems. Signals are messages that inform the processes about certain events and actions. The processes can react to the signals by performing predefined or user-defined actions, such as terminating, suspending, resuming, or ignoring. The -TERM option specifies the signal name or number that the kill command should send. The TERM signal, which stands for terminate, is the default signal that the kill command sends if no option is specified. The TERM signal requests the process to terminate gracefully, by closing any open files, releasing any resources, and performing any cleanup tasks. However, if the process does not respond to the TERM signal, the kill command can send a stronger signal, such as the KILL signal, which forces the process to terminate immediately, without any cleanup. The administrator should use the command kill -TERM to forcibly stop the process. This is the correct answer to the question. The other options are incorrect because they either do not terminate the process (kill -1 or kill -3) or do not terminate the process forcibly (kill -15 or kill -HUP). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 14: Managing Processes, page 431.

The command ip route add 10.0.213.5/32 via 10.0.5.1 dev eth0 adds a static route to the routing table that sends packets destined for 10.0.213.5/32 (a single host) through the gateway 10.0.5.1 on the interface eth0. This is the correct way to achieve the goal. The other options are incorrect because they either use the wrong syntax (route -i etho -p add), the wrong command (route modify), or the wrong file (/proc/net/route). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 12: Managing Network Connections, page 379.

The command sed -i 's/auto/persistent/g' /etc/systemd/journald.conf && sed -i 'persistent/s/ˆ#//q' /etc/systemd/journald.conf will accomplish the task of guaranteeing the persistency of journal log files across system reboots. The sed command is a tool for editing text files on Linux systems. The -i option modifies the file in place. The s command substitutes one string for another. The g flag replaces all occurrences of the string. The && operator executes the second command only if the first command succeeds. The q command quits after the first match. The /etc/systemd/journald.conf file is a configuration file for the systemd-journald service, which is responsible for collecting and storing log messages. The command sed -i 's/auto/persistent/g' /etc/systemd/journald.conf will replace the word auto with the word persistent in the file. This will change the value of the Storage option, which controls where the journal log files are stored. The value auto means that the journal log files are stored in the volatile memory and are lost after reboot, while the value persistent means that the journal log files are stored in the persistent storage and are preserved across reboots. The command sed -i 'persistent/s/ˆ#//q' /etc/systemd/journald.conf will remove the # character at the beginning of the line that contains the word persistent. This will uncomment the Storage option and enable it. The command sed -i 's/auto/persistent/g' /etc/systemd/journald.conf && sed -i 'persistent/s/ˆ#//q' /etc/systemd/journald.conf will guarantee the persistency of journal log files across system reboots by changing and enabling the Storage option to persistent. This is the correct command to use to accomplish the task. The other options are incorrect because they either do not change the value of the Storage option (grep -i auto /etc/systemd/journald.conf && systemct1 restart systemd-journald.service or cat /etc/systemd/journald.conf | awk '(print $1,$3)') or do not enable the Storage option (journalctl --list-boots && systemct1 restart systemd-journald.service). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 16: Managing Logging and Monitoring, page 489.

The docker exec ls command can be used to verify whether the built container has the app.go file in its root directory. This command will run the ls command inside the specified container and list the files and directories in its root directory. If the app.go file is present, it will be displayed in the output. The docker image inspect command will display information about an image, not a container, and it will not list the files inside the image. The docker container inspect command will display information about a container, not its files. The docker ps command is invalid, as ps does not accept a container name as an argument. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 16: Virtualization and Cloud Technologies, page 499.

The administrator should modify the /etc/hosts file and change the db.example.com entry to 192.168.20.88 to address the issue. The /etc/hosts file is a file that maps hostnames to IP addresses on Linux systems. The file can be used to override the DNS resolution and provide a local lookup for hostnames. The dig output shows that the DNS returns the IP address 192.168.20.88 for the hostname db.example.com, which is the correct IP address of the system. The grep output shows that the /etc/hosts file contains an entry for db.example.com with the IP address 192.168.20.89, which is the wrong IP address of the system. This can cause a conflict and prevent the system from being accessed by the hostname. The administrator should modify the /etc/hosts file and change the db.example.com entry to 192.168.20.88, which is the correct IP address of the system. This will align the /etc/hosts file with the DNS and allow the system to be accessed by the hostname. The administrator should modify the /etc/hosts file and change the db.example.com entry to 192.168.20.88 to address the issue. This is the correct answer to the question. The other options are incorrect because they either do not modify the /etc/hosts file (modify the /etc/network file and change the db.example.com entry to 192.168.20.88 or modify the /etc/network file and change the db.example.com entry to 192.168.20.89) or do not change the IP address to the correct one (modify the /etc/hosts file and change the db.example.com entry to 192.168.20.89). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 12: Managing Network Connections, page 378.

To prevent certain files from being tracked by Git, the administrator can use a .gitignore file (B) in the repository. The .gitignore file can specify patterns of files or directories that Git should ignore. This way, the Terraform state files will not appear in the main branch or any other branch. The other commands are not related to this requirement. References:

[CompTIA Linux+ Study Guide], Chapter 10: Working with Git, Section: Ignoring Files with .gitignore

[How to Use .gitignore File]

 The process that will accomplish the task of creating a custom script to run at boot as part of the system services is:

Create a unit file in the /etc/systemd/system/ directory. A unit file is a configuration file that defines the properties and behavior of a systemd service. The systemd is a system and service manager that controls the startup and operation of Linux systems. The /etc/systemd/system/ directory is the location where the administrator can create and store custom unit files. The unit file should have a name that matches the name of the script, such as cleanup.service, and should contain the following sections and options:

[Unit]: This section provides the general information about the service, such as the description, dependencies, and conditions. The administrator should specify the following options in this section:

Description: A brief description of the service, such as “Custom cleanup script”.

After: The name of another unit that this service should start after, such as “network.target”.

ConditionPathExists: The path of the file or directory that must exist for the service to start, such as “/opt/scripts/cleanup.sh”.

[Service]: This section defines how the service should be started and stopped, and what commands should be executed. The administrator should specify the following options in this section:

Type: The type of the service, such as “oneshot”, which means that the service will run once and then exit.

ExecStart: The command that will start the service, such as “/bin/bash /opt/scripts/cleanup.sh”.

RemainAfterExit: A boolean value that indicates whether the service should remain active after the command exits, such as “yes”.

[Install]: This section defines how the service should be enabled and under what circumstances it should be started. The administrator should specify the following option in this section:

WantedBy: The name of another unit that wants this service to be started, such as “multi-user.target”, which means that the service will be started when the system reaches the multi-user mode.

Run the command systemct1 enable cleanup. This command will enable the service and create the necessary symbolic links to start the service at boot.

Run the command systemct1 is-enabled cleanup. This command will check the status of the service and confirm that it is enabled.

This process will create a custom script, cleanup.sh, to run at boot as part of the system services. This is the correct process to use to accomplish the task. The other options are incorrect because they either use the wrong directory for the unit file (/etc/default/, /etc/skel/, or /etc/sysctl.d/) or do not create a unit file at all. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 15: Managing System Services, pages 457-459.

The tool that is best suited to orchestrate a large number of containers across many different servers is Kubernetes. Kubernetes is an open-source platform for managing containerized applications and services. Kubernetes allows the administrator to deploy, scale, and update containers across a cluster of servers, as well as to automate the configuration and coordination of the containers. Kubernetes also provides features such as service discovery, load balancing, storage management, security, monitoring, and logging. Kubernetes can handle complex and dynamic workloads and ensure high availability and performance of the containers. Kubernetes is the tool that is best suited to orchestrate a large number of containers across many different servers. This is the correct answer to the question. The other options are incorrect because they either do not orchestrate containers (Ansible or Terraform) or do not operate across many different servers (Podman). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Cloud and Virtualization Technologies, page 573.

The command firewall-cmd --query-service http will accomplish the task of checking whether web traffic has already been allowed through the firewall. The firewall-cmd command is a tool for managing firewalld, which is a firewall service that provides dynamic and persistent network security on Linux systems. The firewalld uses zones and services to define the rules and policies for the network traffic. The zones are logical groups of network interfaces and sources that have the same level of trust and security. The services are predefined sets of ports and protocols that are associated with certain applications or functions. The --query-service http option queries whether a service is enabled in a zone. The http is the name of the service that the command should check. The http service represents the web traffic that uses the port 80 and the TCP protocol. The command firewall-cmd --query-service http will check whether the http service is enabled in the default zone, which is usually the public zone. The command will return yes if the web traffic has already been allowed through the firewall, or no if the web traffic has not been allowed through the firewall. This is the correct command to use to accomplish the task. The other options are incorrect because they either do not exist (firewalld query-service-http or firewalld --check-service http) or do not query the service (firewall-cmd --check-service http instead of firewall-cmd --query-service http). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 12: Managing Network Connections, page 392.

The command vmstat will most likely be run next by the administrator to troubleshoot the system performance. The vmstat command is a tool for reporting virtual memory statistics on Linux systems. The command shows information about processes, memory, paging, block IO, interrupts, and CPU activity. The command can help the administrator identify the source of the performance issue, such as high CPU usage, low free memory, excessive swapping, or disk IO bottlenecks. The command can also be used with an interval and a count to display the statistics repeatedly over time and observe the changes. The command vmstat will provide useful information for diagnosing the system performance and finding the root cause of the issue. This is the most likely command to run next after the top command. The other options are incorrect because they either do not show the virtual memory statistics (strace or lsof) or do not provide more information than the top command (htop). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 14: Managing Processes and Scheduling Tasks, page 425.

The correct order of Git commands to add a new configuration file to a Git repository is pull -> add -> commit -> push. The pull command will fetch and merge the changes from the remote repository to the local repository, ensuring that the local repository is up to date. The add command will stage the new configuration file for the next commit, marking it as a new file to be tracked by Git. The commit command will create a new snapshot of the project state with the new configuration file and a descriptive message. The push command will publish the commit to the remote repository, updating the remote branch with the new configuration file. The pull -> push -> add -> checkout order is incorrect, as it will not create a commit for the new configuration file, and it will switch to a different branch without pushing the changes. The checkout -> push -> add -> pull order is incorrect, as it will switch to a different branch before adding the new configuration file, and it will overwrite the local changes with the remote changes without creating a commit. The pull -> add -> push -> commit order is incorrect, as it will not create a commit before pushing the changes, and it will create a commit that is not synchronized with the remote branch. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 20: Writing and Executing Bash Shell Scripts, page 579.

The remediation step that will prevent the web service from running as a privileged user is adding the User=webservice to the [Service] section of the service file. The service file is a configuration file that defines the properties and behavior of a systemd service. The systemd is a system and service manager that controls the startup and operation of Linux systems. The service file contains various sections and options that specify how the service should be started, stopped, and managed. The [Service] section defines how the service should be executed and what commands should be run. The User option specifies the user name or ID that the service should run as. The webservice is the name of the user that the administrator wants to run the web service as. The administrator should add the User=webservice to the [Service] section of the service file, which will prevent the web service from running as a privileged user, such as root, and improve the security of the system. This is the correct remediation step to use to prevent the web service from running as a privileged user. The other options are incorrect because they either do not change the user that the service runs as (removing the ExecStart=/usr/sbin/webserver -D OPTIONS from the service file or updating the EnvironmentFile line in the [Service] section to /home/webservice/config) or do not affect the user that the service runs as (changing the multi-user.target in the [Install] section to basic.target). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 15: Managing System Services, page 458.

The user1 password is expired. This can be inferred from the output of the chage -l user1 command, which shows the password expiration information for user1. The output shows that the password expired on 2020-10-01, and the account expired on 2020-10-08. This means that user1 cannot log in to the server unless the password and account are reactivated by the system administrator.

The other options are not correct based on the outputs above. User1 does not need to set a long password, because the output of the passwd -S user1 command shows that the password has a minimum length of 5 characters, which is met by user1’s password. User1 is not in the incorrect group, because the output of the groups user1 command shows that user1 belongs to the app group, which is presumably the correct group for accessing the server. The user1 shell assignment is not incorrect, because the output of the grep user1 /etc/passwd command shows that user1 has /bin/bash as the default shell, which is a valid and common shell for Linux users.

The slowness is caused by the CPU being overloaded. The iostat command shows that the CPU utilization is 100%, which means that there are more processes competing for CPU time than the CPU can handle. The other options are incorrect because:

The system is not running out of swap space, as shown by the iostat command, which shows that there is no swap activity (si and so columns are zero).

The memory is not exhausted, as shown by the free -m command, which shows that there is still available memory (avail column) and free buffer/cache memory (buff/cache column).

The processes are not paging, as shown by the vmstat command, which shows that there are no major page faults (majflt column) and no swap activity (si and so columns). References: CompTIA Linux+ Study Guide, Fourth Edition, page 417-419, 424-425.

The administrator should place the public keys for the server in the ~/.ssh/authorized_keys file. The SSH (Secure Shell) protocol is a method for establishing secure and encrypted connections between remote systems. The SSH protocol supports two types of authentication: password-based and key-based. Password-based authentication requires the user to enter the password of the remote system every time they connect. Key-based authentication requires the user to generate a pair of cryptographic keys: a public key and a private key. The public key is stored on the remote system, while the private key is kept on the local system. The public key and the private key are mathematically related, but not identical. The SSH protocol uses the keys to verify the identity of the user and establish a secure connection without requiring a password. The ~/.ssh/authorized_keys file is a file that contains the public keys of the users who are allowed to connect to the remote system using key-based authentication. The administrator should place the public keys for the server in this file, one per line, and set the appropriate permissions for the file. The administrator should also configure the SSH server to enable key-based authentication by editing the /etc/ssh/sshd_config file and setting the option PasswordAuthentication to no. The administrator should place the public keys for the server in the ~/.ssh/authorized_keys file. This is the correct answer to the question. The other options are incorrect because they are not the standard locations for the public keys for the server (~/.sshd/authkeys, ~/.ssh/keys, or ~/.ssh/keyauth). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 17: Implementing Basic Security, page 513.

The free -h command can be used to check the amount of free and used memory in the system in a human-readable format. This can help to troubleshoot the issue of mysqld being killed due to out of memory. The vmstat -a 1 4 command can be used to monitor the system’s virtual memory statistics, such as swap usage, paging activity, and memory faults, every one second for four times. This can help to identify any memory pressure or performance issues that may cause out of memory errors. The nc -v 127.0.0.1 3306 command would attempt to connect to the MySQL server on port 3306 and display any diagnostic messages, but this would not help to troubleshoot the memory issue. The renice -15 $( pidof mysql ) command would change the priority of the mysql process to -15, but this would not prevent it from being killed due to out of memory. The lsblk command would display information about block devices, not memory usage. The killall -15 command would send a SIGTERM signal to all processes with a matching name, but this would not help to troubleshoot the memory issue. References: [CompTIA Linux+ (XK0-005) Certification Study Guide], Chapter 15: Managing Memory and Process Execution, pages 468-469.

Some good security practices when hardening a Linux server are:

Removing unnecessary packages (B) to reduce the attack surface and eliminate potential vulnerabilities

Disabling the SSH root login possibility (E) to prevent unauthorized access and brute-force attacks on the root account References:

[CompTIA Linux+ Study Guide], Chapter 9: Securing Linux, Section: Hardening Linux

[How to Harden Your Linux Server]

The command ss -pint will allow the administrator to obtain the needed information about processes that are listening on the network ports of a Linux server. The ss command is a tool for displaying socket statistics on Linux systems. Sockets are endpoints of network communication that allow processes to exchange data over the network. The ss command can show various information about the sockets, such as the state, address, port, protocol, and process. The -pint option specifies the filters and flags that the ss command should apply. The -p option shows the process name and ID that owns the socket. The -i option shows the internal information about the socket, such as the send and receive queue, the congestion window, and the retransmission timeout. The -n option shows the numerical address and port, instead of resolving the hostnames and service names. The -t option shows only the TCP sockets, which are the most common type of sockets used for network communication. The command ss -pint will display the socket statistics for the TCP sockets, along with the process name and ID, the numerical address and port, and the internal information. This will allow the administrator to obtain the needed information about processes that are listening on the network ports of a Linux server. This is the correct command to use to obtain the needed information. The other options are incorrect because they either do not show the socket statistics (tcpdump -nL or lsof -It) or do not show the process name and ID (netstat -pn). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 12: Managing Network Connections, page 389.

To unlock an account that has been locked due to login failures, the administrator can use the command pam_tally2 --user=dev2 --reset (D). This will reset the failure counter for the user “dev2” and allow the user to log in again. The other commands will not unlock the account, but either display or increase the failure count. References:

[CompTIA Linux+ Study Guide], Chapter 4: Managing Users and Groups, Section: Locking Accounts with pam_tally2

[How to Lock and Unlock User Account in Linux]

The command that will allow the technician to execute the services and continue deploying other microservices within the same terminal session is bg %1 job name. This command will send the job with ID 1 and name job name to the background, where it will run without occupying the terminal. The other options are incorrect because:

gedit & disown will launch a graphical text editor in the background and detach it from the terminal, but it will not execute any service.

kill 9 %1 will terminate the job with ID 1 using a SIGKILL signal, which cannot be ignored or handled by the process.

fg %1 will bring the job with ID 1 to the foreground, where it will occupy the terminal until it finishes or is stopped. References: CompTIA Linux+ Study Guide, Fourth Edition, page 181-182.

Using AD Query, the security gateway connects to the Active Directory Domain Controllers using Lightweight Directory Access Protocol (LDAP). LDAP is a protocol that provides access to directory services over a network. AD Query uses LDAP queries to retrieve information about users and groups from Active Directory Domain Controllers without installing any software on them. AD Query does not use Windows Management Instrumentation (WMI), Hypertext Transfer Protocol Secure (HTTPS), or Remote Desktop Protocol (RDP) to connect to Active Directory Domain Controllers. References: Check Point Certified Security Administrator (CCSA) R80.x Study Guide, Chapter 5: User Management and Authentication, page 69.

The xfs repair command is used to check and repair an XFS filesystem, which is the type of filesystem used for the /data partition, as shown in the output. The administrator needs to unmount the /data partition before running the xfs repair command on it, and then mount it back after the repair is done. For example: umount /data; xfs_repair /dev/sdcl; mount /data. The mkfs.xfs command is used to create a new XFS filesystem, which would erase all the data on the partition. The fsck command is used to check and repair other types of filesystems, such as ext4, but not XFS. The pvs command is used to display information about physical volumes in a logical volume manager (LVM) setup, which is not relevant for this issue.

 The command that should be run on the DNS forwarder server to accomplish the task is firewall-cmd --zone=public --add-port=53/udp --permanent. The firewall-cmd command is a tool for managing firewalld, which is a firewall service that provides dynamic and persistent network security on Linux systems. The firewalld uses zones and services to define the rules and policies for the network traffic. The zones are logical groups of network interfaces and sources that have the same level of trust and security. The services are predefined sets of ports and protocols that are associated with certain applications or functions. The --zone=public option specifies the zone name that the rule applies to. The public zone is the default zone that represents the untrusted network, such as the internet. The --add-port=53/udp option adds a port and protocol to the zone. The 53 is the port number that is used by the DNS service. The udp is the protocol that is used by the DNS service. The --permanent option makes the change persistent across reboots. The command firewall-cmd --zone=public --add-port=53/udp --permanent will modify the firewall on the server for the DNS forwarder to allow the internal servers to communicate to it and make the changes persistent between server reboots. This is the correct command to use to accomplish the task. The other options are incorrect because they either do not modify the firewall on the server for the DNS forwarder (ufw allow out dns or systemct1 reload firewalld) or do not use the correct syntax for the command (iptables -A OUTPUT -p udp -ra udp -dport 53 -j ACCEPT instead of iptables -A OUTPUT -p udp -ra udp --dport 53 -j ACCEPT). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 12: Managing Network Connections, page 392.

"A service mesh controls the delivery of service requests in an application. Common features provided by a service mesh include service discovery, load balancing, encryption and failure recovery."

The technology that provides load balancing, encryption, and observability in containerized environments is service mesh. A service mesh is a dedicated infrastructure layer that manages the communication and security between microservices in a distributed system. A service mesh consists of two components: a data plane and a control plane. The data plane is composed of proxies that are deployed alongside the microservices as sidecar pods. The proxies handle the network traffic between the microservices and provide features such as load balancing, encryption, authentication, authorization, routing, and observability. The control plane is responsible for configuring and managing the data plane and providing a unified interface for the administrators and developers. A service mesh can help improve the performance, reliability, and security of containerized applications and simplify the development and deployment process. A service mesh is the technology that provides load balancing, encryption, and observability in containerized environments. This is the correct answer to the question. The other options are incorrect because they either do not provide all the features of a service mesh (virtual private network or overlay network) or are not a technology but a component of a service mesh (sidecar pod). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Cloud and Virtualization Technologies, page 574.

https://www.techtarget.com/searchitoperations/definition/service-mesh

The administrator should replace the failed drive and reconfigure the mirror to recover the volume. The LVM (Logical Volume Manager) is a tool for managing disk space on Linux systems. The LVM allows the administrator to create logical volumes that span across multiple physical volumes, such as hard disks or partitions. The LVM also supports different types of logical volumes, such as linear, striped, or mirrored. A mirrored logical volume is a type of logical volume that creates a copy of the data on another physical volume, providing redundancy and fault tolerance. The output shows that the logical volume is mirrored and that one leg of the mirror has failed due to the underlying physical volume. This means that one of the physical volumes that contains the data of the logical volume is damaged or missing. This can cause data loss and performance degradation. The administrator should replace the failed drive and reconfigure the mirror to recover the volume. The administrator should identify the failed physical volume by using commands such as pvdisplay, vgdisplay, or lvdisplay. The administrator should then remove the failed physical volume from the volume group by using the vgreduce command. The administrator should then install a new drive and create a new physical volume by using the pvcreate command. The administrator should then add the new physical volume to the volume group by using the vgextend command. The administrator should then reconfigure the mirror by using the lvconvert command. The administrator should replace the failed drive and reconfigure the mirror to recover the volume. This is the correct answer to the question. The other options are incorrect because they either do not recover the volume (reboot the server. The volume will automatically go back to linear mode or reboot the server. The volume will revert to stripe mode) or do not preserve the data of the volume (recreate the logical volume). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10: Managing Storage, pages 333-334.

The rpm -qf /etc/httpd/conf/httpd.conf command will identify the RPM package that installed the configuration file. This command will query the database of installed packages and display the name of the package that owns the specified file. The rpm -ql /etc/httpd/conf/httpd.conf command is invalid, as -ql is not a valid option for rpm. The rpm --query /etc/httpd/conf/httpd.conf command is incorrect, as --query requires a package name, not a file name. The rpm -q /etc/httpd/conf/httpd.conf command is incorrect, as -q requires a package name, not a file name. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Packages and Software, page 560.

The mechanism that enables administrators to configure and enforce MFA on a Linux system is PAM. PAM stands for Pluggable Authentication Modules, which is a framework for managing authentication and authorization on Linux systems. PAM allows the administrator to define the rules and policies for accessing various system resources and services, such as login, sudo, ssh, or cron. PAM also supports different types of authentication methods, such as passwords, tokens, biometrics, or smart cards. PAM can be used to implement MFA, which stands for Multi-Factor Authentication, which is a security technique that requires the user to provide more than one piece of evidence to prove their identity. MFA can enhance the security of the system and prevent unauthorized access. PAM enables administrators to configure and enforce MFA on a Linux system. This is the correct answer to the question. The other options are incorrect because they either do not manage authentication and authorization on Linux systems (Kerberos or PKI) or do not support MFA (SELinux). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 17: Implementing Basic Security, page 517.

To retrieve the scripts from a repository and make them available on a local workstation, the junior Linux administrator can use the command git clone ©. This will create a copy of the repository on the local machine, including all the scripts and history. The other commands will not clone the repository, but either fetch, checkout, or branch from an existing repository. References:

[CompTIA Linux+ Study Guide], Chapter 10: Working with Git, Section: Cloning Repositories with Git

[How to Clone a Git Repository]

The lvs command can be used to obtain a list of all volumes that are part of a volume group. This command will display information such as the name, size, attributes, and volume group of each logical volume in the system. The vgs command can be used to obtain a list of all volume groups in the system, not the volumes. The fdisk -1 command is invalid, as -1 is not a valid option for fdisk. The pvs command can be used to obtain a list of all physical volumes in the system, not the volumes. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 14: Managing Disk Storage, page 461.

The dnf update command will accomplish the task of installing the most recent versions of packages on a RPM-based OS. This command will check for available updates from the enabled repositories and apply them to the system. The apt-get upgrade command is used to install updates on a Debian-based OS, not a RPM-based OS. The rpm -a command is invalid, as -a is not a valid option for rpm. The yum updateinfo command will display information about available updates, but it will not install them. The yum check-update command will check for available updates, but it will not install them. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Packages and Software, page 559.

The pkill -9 -f “upload*.sh” command will terminate all of the identified processes. This command will send a SIGKILL signal (-9) to all processes whose full command line matches the pattern “upload*.sh” (-f). This signal will force the processes to terminate immediately without giving them a chance to clean up or save their state. The kill -9 “upload*.sh” command is invalid, as kill requires a process ID (PID), not a pattern. The killall -9 “upload*.sh” command is incorrect, as killall requires an exact process name, not a pattern. The skill -9 “upload*.sh” command is incorrect, as skill requires a username or a session ID (SID), not a pattern. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 15: Managing Memory and Process Execution, page 470.

The ssh-copy-id command is used to copy a public SSH key from a local machine to a remote server and add it to the authorized_keys file, which allows passwordless authentication between the machines. The administrator can use this command to copy the root user’s public key from nodea to nodeb, and vice versa, to enable SSH access between the nodes without entering a password every time. For example: [root@nodea ssh-copy-id -i ~/.ssh/id_rsa root@nodeb]. The ssh command is used to initiate an SSH connection to a remote server, but it does not copy any keys. The scp command is used to copy files securely between machines using SSH, but it does not add any keys to the authorized_keys file. The ssh-add command is used to add private keys to the SSH agent, which manages them for SSH authentication, but it does not copy any keys to a remote server.

The command that would allow this to happen is docker pull nginx. Docker is a software platform that allows the administrator to create, run, and manage containers on Linux systems. Containers are isolated and lightweight environments that can run applications and services without affecting the host system. Docker uses images to create containers, which are files that contain the code, libraries, dependencies, and configuration of the applications and services. Docker uses a registry to store and distribute images, which is a service that hosts and serves images. Docker Hub is the default public registry that provides a large number of official and community images. Nginx is a popular web server and reverse proxy that can run as a container. The command docker pull nginx will download the latest version of the Nginx image from the Docker Hub registry to the local cache, which is the storage location for the images on the host system. This will allow the administrator to provide a new Nginx image from the registry to the local cache. This is the correct command to use to accomplish the task. The other options are incorrect because they either do not download an image from the registry (docker attach nginx or docker commit nginx) or do not exist (docker import nginx). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Cloud and Virtualization Technologies, page 571.

The command that can be used to check for running containers is docker ps. The docker ps command can list all the containers that are currently running on the system. To show all the containers, including those that are stopped, the administrator can use docker ps -a ©. References:

[CompTIA Linux+ Study Guide], Chapter 11: Working with Containers, Section: Managing Containers with Docker

[Docker PS Command with Examples]

The systemct1 reboot command will restore the server to its usual target by rebooting it. This will cause the server to load the default target specified in /etc/systemd/system.conf or /etc/systemd/system/default.target files. The telinit 0 command would shut down the server, not restore it to its usual target. The systemct1 get-default command would display the default target, not change it. The systemct1 emergency command would switch the server to emergency.target mode, which is even more restrictive than rescue.target mode. References: [CompTIA Linux+ (XK0-005) Certification Study Guide], Chapter 17: System Maintenance and Operation, page 516.

The command that will help the administrator install GRUB on the legacy MBR of the SATA hard drive is grub-install /dev/sda. This command will install GRUB on the master boot record (MBR) of the first SATA disk (/dev/sda). The MBR is the first sector of a disk that contains boot code and a partition table. GRUB will overwrite the boot code and place its own code that can load GRUB modules and configuration files from a specific partition.

The other options are not correct commands for installing GRUB on the legacy MBR of the SATA hard drive. The grub-install /dev/hda command will try to install GRUB on the first IDE disk (/dev/hda), which may not exist or may not be bootable. The grub-install /dev/sr0 command will try to install GRUB on the first SCSI CD-ROM device (/dev/sr0), which is not a hard drive and may not be bootable. The grub-install /dev/hd0,0 command is invalid because grub-install does not accept partition names as arguments, only disk names. References: Installing GRUB using grub-install; GRUB Manual

The command rpm -qa | grep kernel lists all the installed kernel packages, and the command uname -a displays the current kernel version. These commands can help the administrator identify the correct version of the /boot/vmlinuz file, which is the kernel image file. The other options are not relevant or helpful for this task. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 8: Managing the Linux Boot Process, page 267.

The file that holds the system configuration for journal when running systemd is /etc/systemd/journald.conf. This file contains various settings that control the behavior of the journald daemon, which is responsible for collecting and storing log messages from various sources. The journald.conf file can be edited to change the default values of these settings, such as the storage location, size limits, compression, and forwarding options of the journal files. The file also supports a drop-in directory /etc/systemd/journald.conf.d/ where additional configuration files can be placed to override or extend the main file. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 18: Automating Tasks; journald.conf(5) - Linux manual page

File attributes are preventing file modification, which is causing the error message. The output of lsattr /home/user/data.txt shows that the file has the immutable attribute (i) set, which means that the file cannot be changed, deleted, or renamed. The command setfacl -b /home/user/data.txt tries to remove the ACL from the file, but fails because of the immutable attribute. The administrator needs to remove the immutable attribute first by using the command chattr -i /home/user/data.txt and then try to remove the ACL again. The other options are incorrect because they are not supported by the outputs. The administrator is using a highly privileged account, as shown by the # prompt. The filesystem is mounted with the correct options, as shown by the output of mount | grep /home. SELinux file context is not denying the ACL changes, as shown by the output of ls -Z /home/user/data.txt. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing Files and Directories, pages 357-358.

The correct command to block the IP address 192.168.10.50 from accessing a Linux server is iptables -A INPUT -s 192.168.10.50 -j DROP. This command appends a rule to the INPUT chain that matches the source address 192.168.10.50 and jumps to the DROP target, which discards the packet. The other commands are incorrect because they either have invalid syntax, wrong parameters, or wrong order of arguments. References: CompTIA Linux+ Study Guide, Fourth Edition, page 457-458.

The command ssh -i "ABC-key.pem" root@10.0.0.1 would allow the administrator to connect securely to the remote server in order to install application software. The ssh command is a tool for establishing secure and encrypted connections between remote systems. The -i option specifies the identity file that contains the private key for key-based authentication. The "ABC-key.pem" is the name of the identity file that contains the private key. The root@10.0.0.1 is the username and the IP address of the remote server. The command ssh -i "ABC-key.pem" root@10.0.0.1 will connect to the remote server using the private key and allow the administrator to install application software. This is the correct command to use to connect securely to the remote server. The other options are incorrect because they either do not use key-based authentication (sftp root@10.0.0.1 or telnet 10.0.0.1 80) or do not use the correct syntax for the command (scp "ABC-key.pem" root@10.0.0.1 instead of scp -i "ABC-key.pem" root@10.0.0.1 or sftp "ABC-key.pem" root@10.0.0.1 instead of sftp -i "ABC-key.pem" root@10.0.0.1). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 17: Implementing Basic Security, page 513.

The command that will provide the correct information about whether files from the wget package have been altered since they were installed is rpm -V wget. This command will use the rpm utility to verify an installed RPM package by comparing information about the installed files with information from the RPM database. The verification process can check various attributes of each file, such as size, mode, owner, group, checksum, capabilities, and so on. If any discrepancies are found, rpm will report them using a single letter code for each attribute.

The other options are not correct commands for verifying an installed RPM package. The rpm -i wget command is invalid because -i is used to install a package from a file, not to verify an installed package. The rpm -qf wget command will query which package owns wget as a file name or path name, but it will not verify its attributes. The rpm -F wget command will freshen (upgrade) an already installed package with wget as a file name or path name, but it will not verify its attributes. References: rpm(8) - Linux manual page; Using RPM to Verify Installed Packages

The command that will maintain version control while making some changes in the IaC declaration templates is git checkout -b . This command uses the git tool, which is a distributed version control system that tracks changes in source code and enables collaboration among developers. The checkout option switches to a different branch in the git repository, where a branch is a pointer to a specific commit in the history. The -b option creates a new branch with the given name, and switches to it. This way, the administrator can make changes in the new branch without affecting the main branch, and later merge them if needed.

The other options are not correct commands for maintaining version control while making some changes in the IaC declaration templates. The git clone https://github.com/comptia/linux±.git command will clone an existing repository from a remote URL to a local directory, but it will not create a new branch for making changes. The git push origin command will push the local changes to a remote repository named origin, but it will not create a new branch for making changes. The git fetch New-Branch command will fetch updates from a remote branch named New-Branch, but it will not create a new branch for making changes. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Source Code; Git - Basic Branching and Merging

The administrator should use the following three commands to resolve the issue of the root filesystem being full:

df -h /. This command will show the disk usage of the root filesystem in a human-readable format. The df command is a tool for reporting file system disk space usage. The -h option displays the sizes in powers of 1024 (e.g., 1K, 234M, 2G). The / specifies the root filesystem. The command df -h / will show the total size, used space, available space, and percentage of the root filesystem. This command will help the administrator identify the problem and plan the solution.

growpart /dev/mapper/rootvg-rootlv. This command will grow the partition that contains the root filesystem to the maximum size available. The growpart command is a tool for resizing partitions on Linux systems. The /dev/mapper/rootvg-rootlv is the device name of the partition, which is a logical volume managed by the Logical Volume Manager (LVM). The command growpart /dev/mapper/rootvg-rootlv will extend the partition to fill the disk space and increase the size of the root filesystem. This command will help the administrator solve the problem and free up space.

lvresize –L +10G -r /dev/mapper/rootvg-rootlv. This command will resize the logical volume that contains the root filesystem and add 10 GB of space. The lvresize command is a tool for resizing logical volumes on Linux systems. The -L option specifies the new size of the logical volume, in this case +10G, which means 10 GB more than the current size. The -r option resizes the underlying file system as well. The /dev/mapper/rootvg-rootlv is the device name of the logical volume, which is the same as the partition name. The command lvresize –L +10G -r /dev/mapper/rootvg-rootlv will increase the size of the logical volume and the root filesystem by 10 GB and free up space. This command will help the administrator solve the problem and free up space.

The other options are incorrect because they either do not affect the root filesystem (fdisk -1 /dev/sdb, pvcreate /dev/sdb, lsblk /dev/sda, or vgextend /dev/rootvg /dev/sdb) or do not use the correct syntax (fdisk -1 /dev/sdb instead of fdisk -l /dev/sdb or parted -l /dev/mapper/rootvg-rootlv instead of parted /dev/mapper/rootvg-rootlv print). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10: Managing Storage, pages 318-319, 331-332.

The command iptables -t filter -A INPUT -p tcp --dport 4000:5000 -j ACCEPT will enforce the rule of allowing incoming traffic to ports in the range of 4000 to 5000 on a Linux server. The iptables command is a tool for managing firewall rules on Linux systems. The -t option specifies the table to operate on, in this case filter, which is the default table that contains the rules for filtering packets. The -A option appends a new rule to the end of a chain, in this case INPUT, which is the chain that processes the packets that are destined for the local system. The -p option specifies the protocol to match, in this case tcp, which is the transmission control protocol. The --dport option specifies the destination port or port range to match, in this case 4000:5000, which is the range of ports from 4000 to 5000. The -j option specifies the target to jump to if the rule matches, in this case ACCEPT, which is the target that allows the packet to pass through. The command iptables -t filter -A INPUT -p tcp --dport 4000:5000 -j ACCEPT will add a new rule to the end of the INPUT chain that will accept the incoming TCP packets that have a destination port between 4000 and 5000. This command will enforce the rule and allow the traffic to the specified ports. This is the correct command to use to accomplish the task. The other options are incorrect because they either use the wrong options (-f instead of -t or -D instead of -A) or do not exist (iptables filter -A INPUT -p tcp --dport 4000:5000 -D ACCEPT or iptables filter -S INPUT -p tcp --dport 4000:5000 -A ACCEPT). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 18: Securing Linux Systems, page 543.

The command that can be used to remove an RPM package that was installed by mistake is dnf remove packagename. This command will use the DNF package manager to uninstall an RPM package and its dependencies from a Linux system that uses RPM-based distributions, such as Red Hat Enterprise Linux or CentOS. The DNF package manager handles dependency resolution and metadata searching for RPM packages.

The other options are not correct commands for removing an RPM package from a Linux system. The apt-get remove packagename and apt remove packagename commands are used to remove Debian packages from a Linux system that uses Debian-based distributions, such as Ubuntu or Debian. They are not compatible with RPM packages. The rpm -i packagename command is used to install an RPM package, not to remove it. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 9: Managing Software Packages; How to install/remove/query/update RPM packages in Linux (Cheat Sheet …

The administrator should increase the TimeoutStartUSec configuration for the logsearch.service to resolve the issue. The output of systemct1 status logsearch.service shows that the service failed to start due to a timeout. The output of cat /etc/systemd/system/logsearch.service shows that the service has a TimeoutStartUSec configuration of 10 seconds, which might be too short for the service to start. The administrator should increase this value to a higher number, such as 30 seconds or 1 minute, and then restart the service. The other options are incorrect because they are not related to the issue. The service is already enabled, as shown by the output of systemct1 is-enabled logsearch.service. The service does not use an OnCalendar configuration, as it is not a timer unit. The service does not use a KillSignal configuration, as it is not being killed by a signal. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 14: Managing Processes and Scheduling Tasks, pages 434-435.

The docker image tag test test:v1 command can be used to assign the v1 version to the image called test. This command creates a new tag for the existing image, without changing the original image. The docker image save test test:v1 command would save the image to a file, not assign a version. The docker image build test:vl command is invalid, as vl is not a valid version number. The docker image version test:v1 command does not exist. References: [CompTIA Linux+ (XK0-005) Certification Study Guide], Chapter 16: Virtualization and Cloud Technologies, page 500.

The file /etc/ssh/sshd_config contains the configuration settings for the SSH daemon, which handles the secure remote login. To change the port number, the engineer should edit this file and modify the line that says Port 22 to Port 49000. The other files are not related to the SSH service. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 13: Managing Network Services, page 411.

The command that will permanently resolve the issue of high CPU load and average is kill -9 6295. This command will send a SIGKILL signal to the process with the PID 6295, which is the process that is consuming 99.7% of the CPU according to the top output. The SIGKILL signal will terminate the process immediately and free up the CPU resources. The kill command is used to send signals to processes by PID or name.

The other options are not correct commands for resolving this issue. The renice -n -20 6295 command will change the priority (niceness) of the process with PID 6295 to -20, which is the highest priority possible. This will make the process more CPU-intensive, not less. The renice command is used to change the priority of running processes. The pstree -p 6295 command will show a tree of processes with PID 6295 as the root. This will not affect the CPU load or average, but only display information. The pstree command is used to display a tree of processes. The iostat -cy 1 5 command will show CPU and disk I/O statistics for 5 iterations with an interval of 1 second. This will also not affect the CPU load or average, but only display information. The iostat command is used to report CPU and I/O statistics. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Troubleshooting Linux Systems; kill(1) - Linux manual page; renice(1) - Linux manual page; pstree(1) - Linux manual page; iostat(1) - Linux manual page

The command git clone https://git.company.com/admin/project.git will achieve the goal of downloading a Git repository from the given URL. The git command is a tool for managing version control systems. The clone option creates a copy of an existing repository. The URL specifies the location of the repository to clone, in this case https://git.company.com/admin/project.git. The command git clone https://git.company.com/admin/project.git will download the repository and create a directory named project in the current working directory. This is the correct command to use to accomplish the goal. The other options are incorrect because they either do not download the repository (git checkout, git pull, or git branch) or do not use the correct syntax (git checkout https://git.company.com/admin/project.git instead of git checkout -b project https://git.company.com/admin/project.git or git branch https://git.company.com/admin/project.git instead of git branch project https://git.company.com/admin/project.git). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Cloud and Virtualization Technologies, page 571.

 The command docker images prune -a will help to remove all dangling images and delete all the images that do not have an associated container. The docker command is a tool for managing Docker containers and images. The images subcommand operates on images. The prune option removes unused images. The -a option removes all images, not just dangling ones. A dangling image is an image that is not tagged and is not referenced by any container. This command will accomplish the task of cleaning up the unused images. The other options are incorrect because they either do not exist (docker push images -a or docker images rmi --all) or do not remove images (docker rmi -a images only removes images that match the name or ID of “images”). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Cloud and Virtualization Technologies, page 567.

The tool that is commonly used for creating CI/CD pipelines is Jenkins. Jenkins is an open-source automation server that enables continuous integration and continuous delivery (CI/CD) of software projects. Jenkins allows developers to build, test, and deploy code changes automatically and frequently using various plugins and integrations. Jenkins also supports distributed builds, parallel execution, pipelines as code, and real-time feedback. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Source Code; Jenkins

The command that can be used to resolve the issue of being unable to remove a particular data folder is chattr -R -i data/. This command will use the chattr utility to change file attributes on a Linux file system. The -R option means that chattr will recursively change attributes of directories and their contents. The -i option means that chattr will remove (unset) the immutable attribute from files or directories. When a file or directory has the immutable attribute set, it cannot be modified, deleted, or renamed.

The other options are not correct commands for resolving this issue. The chgrp -R 755 data/ command will change the group ownership of data/ and its contents recursively to 755, which is not a valid group name. The chgrp command is used to change group ownership of files or directories. The chmod -R 777 data/ command will change the file mode bits of data/ and its contents recursively to 777, which means that everyone can read, write, and execute them. However, this will not remove the immutable attribute, which prevents deletion or modification regardless of permissions. The chmod command is used to change file mode bits of files or directories. The chown -R data/ command is incomplete and will produce an error. The chown command is used to change the user and/or group ownership of files or directories, but it requires at least one argument besides the file name. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 7: Managing Disk Storage; chattr(1) - Linux manual page; chgrp(1) - Linux manual page; chmod(1) - Linux manual page; chown(1) - Linux manual page

The command tail -n 20 will display the last 20 lines of a file. The -n option specifies the number of lines to show. This is the correct command to execute the task. The other options are incorrect because they either use the wrong options (-v, -c, or -l) or have the wrong arguments (20 instead of 20 filename). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing Files and Directories, page 352.

To allow SFTP (which uses port 22, same as SSH) from a specific subnet using UFW, the most specific and correct syntax is:

bash

sudo ufw allow from 10.10.0.0/24 to any port 22

This allows traffic from a specific subnet to port 22, which is what’s required.

Option B allows traffic on an interface but is not limited to the subnet.

Option C is incomplete — it allows all ports from the subnet.

Option D is malformed syntax — 0:22/tcp is not a valid port range or UFW format.

The output shows that the user1 account has a locked password, indicated by the exclamation point (!) in the second field of the /etc/shadow file1. To unlock the password and allow the user to log in, the systems administrator should use the passwd command with the -u (unlock) option2.

Step-by-Step Comprehensive Detailed Explanation:

Command Explanation:

xfs_repair is the correct tool to repair XFS filesystems. It scans the filesystem metadata for errors and attempts to fix any corruption.

Why Other Options are Incorrect:

A: fdisk is used to manage partitions, not repair filesystems.

C: lvcreate is for creating logical volumes, not repairing filesystems.

D: fsck.ext4 is used for ext4 filesystems, but /opt/finapp is an XFS filesystem.

netstat is a command-line tool that displays network connections, routing tables, and a number of network interface statistics. It can be used to check if the SSHD service is listening on its default port (usually port 22) or any other configured port.

The oom-killer is invoked when the system runs out of memory, as indicated by the memory usage in the free -m output. Since swap space is not being used and physical memory is almost entirely consumed, adding more memory resources will prevent the system from running out of memory and invoking the oom-killer to terminate processes.

The /etc/skel directory (note: the correct spelling is skel, not ske1) contains default files and folders that are copied into a new user’s home directory when the account is created.

A is intended to be /etc/skel and is correct if the typo is fixed.

Corrected Question Should Use: A. /etc/skel

Incorrect Options:

B: Used for network/system configuration.

C: Contains SSH server configuration and keys.

D: A script run at system boot — unrelated to user home configuration.

The nice command is used to start a process with a user-defined scheduling priority. The higher the nice value, the lower the process priority.

Option B is correct. By default, nice starts a command with a nice value of 10, which reduces its CPU priority and allows more critical processes to take precedence.

Incorrect Options:

A: Incorrect syntax; --nice is not a valid option for most binaries.

C: -15 would increase the priority (negative nice values raise the process priority) — the opposite of what's intended.

D: Invalid syntax and improper backgrounding.

Comprehensive and Detailed Step-by-Step Explanation:

0 9 * * 6,0 ensures execution at 9:00 AM on Saturdays (6) and Sundays (0).

1-5 would run the script Monday-Friday.

*/3 is incorrect because it runs every three days.

1 * * runs only on the 1st day of each month.

pvs shows warning that a PV is missing.

The LVM volume vgdata-lvdata cannot be mounted.

Step-by-Step Comprehensive Detailed Explanation:

Command Explanation:

mkdir CompTIA_doc creates the directory, and && ensures the cd CompTIA_doc command executes only if the directory creation is successful.

Why Other Options are Incorrect:

A: The & runs commands in the background and does not ensure sequential execution.

B: + is not a valid operator in shell commands.

C: || executes the second command only if the first command fails.

The umask determines the default permission for new files. To get -rw-r--r-- (644), the umask should be set to 0027. This sets the permissions to allow read and write for the owner, read-only for the group, and no permissions for others.

The correct answer is D. git checkout -b staging

This command will create a new branch named staging and switch to it. The git checkout command is used to switch between branches or restore files from a specific branch. The -b option is used to create a new branch if it does not exist. For example, git checkout -b staging will create and switch to the staging branch.

The other options are incorrect because:

A. git branch -m staging

This command will rename the current branch to staging, not switch to it. The git branch command is used to list, create, or delete branches. The -m option is used to rename a branch. For example, git branch -m staging will rename the current branch to staging.

B. git commit -m staging

This command will commit the changes in the working tree to the current branch with a message of staging, not switch to it. The git commit command is used to record changes to the repository. The -m option is used to specify a commit message. For example, git commit -m staging will commit the changes with a message of staging.

C. git status -b staging

This command will show the status of the working tree and the current branch, not switch to it. The git status command is used to show the state of the working tree and the staged changes. The -b option is used to show the name of the current branch. However, this option does not take an argument, so specifying staging after it will cause an error.