CompTIA CompTIA Certifications XK0-005 Questions & Answers

• Question 221:

  Which of the following commands is used to configure the default permissions for new files?

  A. setenforce

  B. sudo

  C. umask

  D. chmod

  Correct Answer: C

  Explanation: The command that is used to configure the default permissions for new files is umask. 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. The command that is used to configure the default permissions for new files is umask. This is the correct answer to the question. The other options are incorrect because they either do not set the default permissions for new files (setenforce, sudo, or chmod) or do not exist (kill -HUP or kill -TERM). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 11: Managing File Permissions and Ownership, page 349.

• Question 222:

  An administrator thinks that a package was installed using a snap. Which of the following commands can the administrator use to verify this information?

  A. snap list

  B. snap find

  C. snap install

  D. snap try

  Correct Answer: A

  The snap list command is used to display the installed snaps on the system1. Snaps are self-contained software packages that can be installed and updated across different Linux distributions2. The snap list command shows the name,

  version, revision, developer and notes of each snap1.

  The snap find command is used to search for snaps in the Snap Store, which is an online repository of snaps2. The snap install command is used to install snaps from the Snap Store or from a local file2. The snap try command is used to test

  a snap without installing it, by mounting a directory that contains the snap files2. These commands are not useful for verifying if a package was installed using a snap.

• Question 223:

  A systems administrator wants to test the route between IP address 10.0.2.15 and IP address 192.168.1.40. Which of the following commands will accomplish this task?

  A. route -e get to 192.168.1.40 from 10.0.2.15

  B. ip route get 192.163.1.40 from 10.0.2.15

  C. ip route 192.169.1.40 to 10.0.2.15

  D. route -n 192.168.1.40 from 10.0.2.15

  Correct Answer: B

  Explanation: 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.

• Question 224:

  A cloud engineer needs to check the link status of a network interface named eth1 in a Linux server. Which of the following commands can help to achieve the goal?

  A. ifconfig hw eth1

  B. netstat -r eth1

  C. ss -ti eth1

  D. ip link show eth1

  Correct Answer: D

  Explanation: 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.

• Question 225:

  A systems administrator wants to upgrade /bin/ someapp to a new version, but the administrator does not know the package name. Which of the following will show the RPM package name that provides that binary file?

  A. rpm --qf /bin/ someapp

  B. rpm --Vv / bin/ someapp

  C. rpm - P / bin/ some app

  D. rpm --i / bin/ someapp

  Correct Answer: A

  The rpm command is used to manage RPM packages on Linux systems. The -qf option queries the package name that provides a given file. Therefore, the command rpm -qf /bin/someapp will show the RPM package name that provides the binary file /bin/someapp. The statements B, C, and D are incorrect because they do not query the package name, but rather verify, remove, or install a package. References: [How to Use RPM Command in Linux with Examples]

• Question 226:

  Users are experiencing high latency when accessing a web application served by a Linux machine. A systems administrator checks the network interface counters and sees the following:

  

  Which of the following is the most probable cause of the observed latency?

  A. The network interface is disconnected.

  B. A connection problem exists on the network interface.

  C. No IP address is assigned to the interface.

  D. The gateway is unreachable.

  Correct Answer: B

  The high number of errors and dropped packets in the output of the network interface counters indicate a connection problem on the network interface.

  References:

  CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10: Managing Networking, Section: Troubleshooting Network Issues, Page 359. Linux+ (Plus) Certification, Exam Objectives: 4.3 Given a scenario, troubleshoot and resolve

  basic network configuration and connectivity issues.

• Question 227:

  A new file was added to a main Git repository. An administrator wants to synchronize a local copy with the contents of the main repository. Which of the following commands should the administrator use for this task?

  A. git reflog

  B. git pull

  C. git status

  D. git push

  Correct Answer: B

  Explanation: 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.

• Question 228:

  A Linux administrator is providing a new Nginx image from the registry to local cache. Which of the following commands would allow this to happen?

  A. docker pull nginx

  B. docker attach nginx

  C. docker commit nginx

  D. docker import nginx

  Correct Answer: A

  Explanation: 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.

• Question 229:

  A Linux engineer finds multiple failed login entries in the security log file for application users. The Linux engineer performs a security audit and discovers a security issue. Given the following:

  # grep -iE '*www*|db' /etc/passwd

  www-data:x:502:502:www-data:/var/www:/bin/bash

  db:x: 505:505:db: /opt/db:/bin/bash

  Which of the following commands would resolve the security issue?

  A. usermod -d /srv/www-data www-data andand usermod -d /var/lib/db db

  B. passwd -u www-data andand passwd -u db

  C. renice -n 1002 -u 502 andand renice -n 1005 -u 505

  D. chsh -s /bin/false www-data andand chsh -s /bin/false db

  Correct Answer: D

  This command will use the chsh tool to change the login shell of the users www-data and db to /bin/false, which means they will not be able to log in to the system1. This will prevent unauthorized access attempts and improve security. References: 1: Replacing /bin/bash with /bin/false in /etc/passwd file

• Question 230:

  As part of the requirements for installing a new application, the swappiness parameter needs to be changed to O. This change needs to persist across re-boots and be applied immediately. A Linux systems administrator is performing this change. Which of the following steps should the administrator complete to accomplish this task?

  A. echo "vm. swappiness--()" >> /etc/sysctl . conf andand sysctl --p

  B. echo "vrn. >> / proc/meminfo andand sysctl --a

  C. sysctl --v >> / proc/meminfo and and echo "vm. swapiness=0"

  D. sysctl --h "vm. swapiness--O" andand echo / etc/vmswapiness

  Correct Answer: A

  To change the swappiness parameter to 0 and make it persistent across reboots and applied immediately, the administrator can perform the following steps:

  Append the line vm.swappiness=0 to the file /etc/sysctl.conf using echo "vm.swappiness=0" >> /etc/sysctl.conf (A). This will set the swappiness parameter to 0 for future boots.

  Reload the sysctl configuration using sysctl -p (A). This will apply the changes to the current system without rebooting. The other commands will not achieve this task, but either write to a wrong file, use a wrong option, or have a syntax error.

  References:

  [CompTIA Linux+ Study Guide], Chapter 8: Optimizing Linux Performance, Section: Tuning Kernel Parameters with sysctl

  [How to Change Swappiness in Linux]