CompTIA XK0-005 Online Practice Questions and Exam Preparation

CompTIA XK0-005 Online Questions & Answers

• Question 61:

  A Linux administrator is trying to start the database service on a Linux server but is not able to run it. The administrator executes a few commands and receives the following output:

  

  Which of the following should the administrator run to resolve this issue? (Select two).

  A. systemctl unmask mariadb
  B. journalctl --g mariadb
  C. dnf reinstall mariadb
  D. systemctl start mariadb
  E. chkconfig mariadb on
  F. service mariadb reload
  A. systemctl unmask mariadb
  D. systemctl start mariadb

  ---

  Explanation

  These commands will unmask the mariadb service, which is currently prevented from starting, and then start it normally. The other commands are either not relevant, not valid, or not sufficient for this task. For more information on how to manage masked services with systemctl, you can refer to the web search result 1.

• Question 62:

  A Linux administrator is enabling root log-in over SSH on a server. Which of the following combinations of files and parameters should the administrator modify to accomplish this task?

  A. /etc/ssh/ssh_config - PermitRootLogin
  B. /etc/ssh/ssh_config - AllowRootLogin
  C. /etc/ssh/sshd_config - PermitRootLogin
  D. /etc/ssh/sshd_config - AllowRootLogin
  C. /etc/ssh/sshd_config - PermitRootLogin

  ---

  Explanation

  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.

  OpenSSH Server Configuration

• Question 63:

  Users have reported that the interactive sessions were lost on a Linux server. A Linux administrator verifies the server was switched to rescue.target mode for maintenance. Which of the following commands will restore the server to its usual target?

  A. telinit 0
  B. systemct1 reboot
  C. systemct1 get-default
  D. systemct1 emergency
  B. systemct1 reboot

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  Explanation

  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.

• Question 64:

  An administrator is trying to diagnose a performance issue and is reviewing the following output:

  

  System Properties:

  CPU: 4 vCPU

  Memory: 40GB

  Disk maximum IOPS: 690

  Disk maximum throughput: 44Mbps | 44000Kbps

  Based on the above output, which of the following BEST describes the root cause?

  A. The system has reached its maximum IOPS, causing the system to be slow.
  B. The system has reached its maximum permitted throughput, therefore iowait is increasing.
  C. The system is mostly idle, therefore the iowait is high.
  D. The system has a partitioned disk, which causes the IOPS to be doubled.
  B. The system has reached its maximum permitted throughput, therefore iowait is increasing.

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  Explanation

  The system has reached its maximum permitted throughput, therefore iowait is increasing. The output of iostat -x shows that the device sda has an average throughput of 44.01 MB/s, which is equal to the disk maximum throughput of 44 Mbps. The output also shows that the device sda has an average iowait of 99.99%, which means that the CPU is waiting for the disk to complete the I/O requests. This indicates that the disk is the bottleneck and the system is slow due to the high iowait. The other options are incorrect because they are not supported by the outputs. The system has not reached its maximum IOPS, as the device sda has an average IOPS of 563.50, which is lower than the disk maximum IOPS of 690. The system is not mostly idle, as the output of top shows that the CPU is 100% busy. The system does not have a partitioned disk, as the output of lsblk shows that the device sda has only one partition sda1.

  References: CompTIA Linux

  + (XK0-005) Certification Study Guide, Chapter 17: Optimizing Linux Systems, pages 513-514.

• Question 65:

  A Linux administrator needs to expand a volume group using a new disk. Which of the following options presents the correct sequence of commands to accomplish the task?

  A. partprobe vgcreate lvextend
  B. lvcreate fdisk partprobe
  C. fdisk partprobe mkfs
  D. fdisk pvcreate vgextend
  D. fdisk pvcreate vgextend

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  Explanation

  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+ (XK0005) Certification Study Guide, Chapter 14: Managing Disk Storage, pages 462-463.

• Question 66:

  A Linux administrator created the directory /project/access2all. By creating this directory, the administrator is trying to avoid the deletion or modification of files from non-owners. Which of the following will accomplish this goal?

  A. chmod +t /project/access2all
  B. chmod +rws /project/access2all
  C. chmod 2770 /project/access2all
  D. chmod ugo+rwx /project/access2all
  A. chmod +t /project/access2all

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  Explanation

  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

• Question 67:

  A Linux engineer needs to block an incoming connection from the IP address 2.2.2.2 to a secure shell server and ensure the originating IP address receives a response that a firewall is blocking the connection. Which of the following commands can be used to accomplish this task?

  A. iptables -A INPUT -p tcp -- dport ssh -s 2.2.2.2 -j DROP
  B. iptables -A INPUT -p tcp -- dport ssh -s 2.2.2.2 -j RETURN
  C. iptables -A INPUT -p tcp -- dport ssh -s 2.2.2.2 -j REJECT
  D. iptables -A INPUT -p tcp -- dport ssh -s 2.2.2.2 -j QUEUE
  C. iptables -A INPUT -p tcp -- dport ssh -s 2.2.2.2 -j REJECT

  ---

  Explanation

  The REJECT target sends back an error packet to the source IP address, indicating that the connection is refused by the firewall. This is different from the DROP target, which silently discards the packet without any response. The RETURN target returns to the previous chain, which may or may not accept the connection. The QUEUE target passes the packet to a userspace application for further processing, which is not the desired outcome in this case. References CompTIA Linux+ (XK0-005) Certification Study Guide, page 316 iptables - ssh - access from specific ip only - Server Fault, answer by Eugene Ionichev

• Question 68:

  A Linux administrator has installed a web server, a database server, and a web application on a server. The web application should be active in order to render the web pages. After the administrator restarts the server, the website displays the following message in the browser: Error establishing a database connection. The Linux administrator reviews the following relevant output from the systemd init files:

  

  The administrator needs to ensure that the database is available before the web application is started. Which of the following should the administrator add to the HTTP server .service file to accomplish this task?

  A. TRIGGERS=mariadb.service
  B. ONFAILURE=mariadb.service
  C. WANTEDBY=mariadb.service
  D. REQUIRES=mariadb.service
  D. REQUIRES=mariadb.service

  ---

  Explanation

  The administrator should add REQUIRES=mariadb.service to the HTTP server .service file to ensure that the database is available before the web application is started. This directive specifies that the HTTP server unit requires the MariaDB server unit to be started before it can run. If the MariaDB server unit fails to start or stops for any reason, the HTTP server unit will also fail or stop. This way, the dependency between the web application and the database is enforced by systemd. The other options are not correct directives for accomplishing this task. TRIGGERS=mariadb.service is not a valid directive in systemd unit files. ONFAILURE=mariadb.service means that the HTTP server unit will start only if the MariaDB server unit fails, which is not what we want. WANTEDBY=mariadb.service means that the HTTP server unit will be started when the MariaDB server unit is enabled, but it does not imply a strong dependency or ordering relationship between them.

  References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10: Managing Services with systemd; systemd.unit(5) - Linux manual page

• Question 69:

  A systems administrator received a notification that a system is performing slowly. When running the top command, the systems administrator can see the following values:

  

  Which of the following commands will the administrator most likely run NEXT?

  A. vmstat
  B. strace
  C. htop
  D. lsof
  A. vmstat

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  Explanation

  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.

• Question 70:

  An administrator needs to allow remote administrative access to a Linux server only to employees who are using the authorized private key. Which of the following options should the administrator set in the SSHD configuration file to achieve the goal?

  A. AuthorizedKeysCommand sudo
  B. PermitRootLogin prohibit-password
  C. AuthorizedKeysCommandUser root
  D. PasswordAuthentication no
  D. PasswordAuthentication no

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  Explanation

  PasswordAuthentication no ensures that SSH logins are only allowed using key- based authentication, preventing password-based access. PermitRootLogin prohibit-password prevents root login via passwords but does not enforce key-

  based authentication for all users.

  AuthorizedKeysCommandUser root is related to custom key authentication scripts and is not necessary for enforcing key-based authentication. AuthorizedKeysCommand sudo is not a valid SSH configuration option.

  CompTIA Linux+ Official Study Guide, Chapter on Secure SSH Configuration