CompTIA CompTIA Certifications XK0-005 Questions & Answers

• Question 71:

  A systems technician is working on deploying several microservices to various RPM-based systems, some of which could run up to two hours. Which of the following commands will allow the technician to execute those services and continue deploying other microservices within the same terminal section?

  A. gedit and disown

  B. kill 9 %1

  C. fg %1

  D. bg %1 job name

  Correct Answer: D

  Explanation: 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 and 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.

• Question 72:

  A Linux administrator is troubleshooting a memory-related issue. Based on the output of the commands:

  

  Which of the following commands would address the issue?

  A. top -p 8321

  B. kill -9 8321

  C. renice -10 8321

  D. free 8321

  Correct Answer: B

  Explanation: 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

• Question 73:

  The application team has reported latency issues that are causing the application to crash on the Linux server. The Linux administrator starts

  troubleshooting and receives the following output:

  

  Which of the following commands will improve the latency issue?

  A. # echo 'net.core.net_backlog = 5000000' >> /etc/sysctl.conf # sysctl -p # systemctl daemon-reload

  B. # ifdown eth0 # ip link set dev eth0 mtu 800 # ifup eth0

  C. # systemctl stop network # ethtool -g eth0 512 # systemctl start network

  D. # echo 'net.core.rmem max = 12500000' >> /etc/sysctl.conf # echo 'net.core.wmem_max = 12500000' >> /etc/sysctl.conf # sysctl -p

  Correct Answer: D

  The best command to use to improve the latency issue is D. # echo `net.core.rmem max = 12500000' >> /etc/sysctl.conf # echo `net.core.wmem_max = 12500000' >> /etc/sysctl.conf # sysctl -p. This command will increase the size of the

  receive and send buffers for the network interface, which can improve the network performance and reduce packet loss. The sysctl command will apply the changes to the kernel parameters without rebooting the system.

  The other commands are either incorrect or not suitable for this task. For example:

  A. # echo `net.core.net_backlog = 5000000' >> /etc/sysctl.conf # sysctl -p # systemctl daemon-reload will try to increase the backlog queue for incoming connections, but this is not relevant for the latency issue. The systemctl daemon- reload command is also unnecessary, as it only reloads the systemd configuration files, not the kernel parameters.

  B. # ifdown eth0 # ip link set dev eth0 mtu 800 # ifup eth0 will try to change the maximum transmission unit (MTU) of the network interface to 800 bytes, but this is too low and may cause fragmentation and performance degradation. The default MTU for Ethernet is 1500 bytes, and it should not be changed unless there is a specific reason.

  C. # systemctl stop network # ethtool -g eth0 512 # systemctl start network will try to change the ring buffer size of the network interface to 512, but this is too small and may cause packet drops and latency spikes. The default ring buffer size for Ethernet is usually 4096 or higher, and it should be increased if there is a high network traffic.

• Question 74:

  A Linux administrator was asked to run a container with the httpd server inside. This container should be exposed at port 443 of a Linux host machine while it internally listens on port 8443. Which of the following commands will accomplish this task?

  A. podman run -d -p 443:8443 httpd

  B. podman run -d -p 8443:443 httpd

  C. podman run -d -e 443:8443 httpd

  D. podman exec -p 8443:443 httpd

  Correct Answer: A

  Explanation: The command that will accomplish the task of running a container with the httpd server inside and exposing it at port 443 of the Linux host machine while it internally listens on port 8443 is podman run -d -p 443:8443 httpd. This command uses the podman tool, which is a daemonless container engine that can run and manage containers on Linux systems. The -d option runs the container in detached mode, meaning that it runs in the background without blocking the terminal. The -p option maps a port on the host machine to a port inside the container, using the format host_port:container_port. In this case, port 443 on the host machine is mapped to port 8443 inside the container, allowing external access to the httpd server. The httpd argument specifies the name of the image to run as a container, which in this case is an image that contains the Apache HTTP Server software. The other options are not correct commands for accomplishing the task. Podman run -d -p 8443:443 httpd maps port 8443 on the host machine to port 443 inside the container, which does not match the requirement. Podman run -d -e 443:8443 httpd uses the -e option instead of the -p option, which sets an environment variable inside the container instead of mapping a port. Podman exec -p 8443:443 httpd uses the podman exec command instead of the podman run command, which executes a command inside an existing container instead of creating a new one. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 18: Automating Tasks

• Question 75:

  A systems administrator wants to permit access temporarily to an application running on port 1234/TCP on a Linux server. Which of the following commands will permit this traffic?

  A. firewall-cmd --new-service=1234/tcp

  B. firewall-cmd --service=1234 --protocol=tcp

  C. firewall-cmd --add--port=1234/tcp

  D. firewall-cmd --add-whitelist-uid=1234

  Correct Answer: C

  The firewall-cmd command is used to manage firewalld, which is a firewall service for Linux systems that provides dynamic and persistent configuration of firewall rules. Firewalld uses zones and services to define different levels of trust and access for network connections. To permit access temporarily to an application running on port 1234/TCP on a Linux server, the systems administrator can use the firewall-cmd --add-port=1234/tcp command. This command will add a rule to the default zone (usually public) that allows incoming traffic on port 1234/TCP. The rule will only be effective until the next reload or restart of firewalld. To make the rule permanent, the administrator can add the --permanent option to the command. The statement C is correct. The statements A, B, and D are incorrect because they do not permit access to port 1234/TCP. The firewall-cmd --new-service=1234/tcp command does not exist. The firewall- cmd --service=1234 --protocol=tcp command does not work because 1234 is not a predefined service name in firewalld. The firewall-cmd --add-whitelist-uid=1234 command does not exist. References: [How to Use FirewallD to Manage Firewall in Linux]

• Question 76:

  During a security scan, the password of an SSH key file appeared to be too weak and was cracked. Which of the following commands would allow a user to choose a stronger password and set it on the existing SSH key file?

  A. passwd

  B. ssh

  C. ssh-keygen

  D. pwgen

  Correct Answer: C

  Explanation: The command that would allow a user to choose a stronger password and set it on the existing SSH key file is ssh-keygen -p -f . This command uses the ssh-keygen tool, which is used to generate, manage, and convert authentication keys for SSH. The -p option stands for passphrase, and it allows the user to change or remove the passphrase of an existing private key file. The -f option specifies the filename of the key file. The command will prompt the user for the old passphrase, and then for the new passphrase twice. The other options are not correct commands for changing the password of an SSH key file. The passwd command is used to change the password of a user account on a Linux system, not an SSH key file. The ssh command is used to log in to a remote system using SSH, not to change the password of an SSH key file. The pwgen command is used to generate random passwords, not to change the password of an SSH key file. References: ssh-keygen(1) - Linux manual page; How To: Change Passphrase for SSH Private Key - Unix Tutorial

• Question 77:

  A Linux administrator is troubleshooting a systemd mount unit file that is not working correctly. The file contains:

  [root@system] # cat mydocs.mount

  [Unit]

  Description=Mount point for My Documents drive

  [Mount]

  What=/dev/drv/disk/by-uuid/94afc9b2-ac34-ccff-88ae-297ab3c7ff34

  Where=/home/user1/My Documents

  Options=defaults

  Type=xfs

  [Install]

  WantedBy=multi-user.target

  The administrator verifies the drive UUID correct, and user1 confirms the drive should be mounted as My Documents in the home directory.

  Which of the following can the administrator do to fix the issues with mounting the drive? (Select two).

  A. Rename the mount file to home-user1-My\x20Documents.mount.

  B. Rename the mount file to home-user1-my-documents.mount.

  C. Change the What entry to /dev/drv/disk/by-uuid/94afc9b2\-ac34\-ccff\-88ae\- 297ab3c7ff34.

  D. Change the Where entry to Where=/home/user1/my\ documents.

  E. Change the Where entry to Where=/home/user1/My\x20Documents.

  F. Add quotes to the What and Where entries, such as What="/dev/drv/disk/by- uuid/94afc9b2-ac34-ccff-88ae-297ab3c7ff34" and Where="/home/user1/My Documents".

  Correct Answer: AE

  The mount unit file name and the Where entry must be escaped to handle spaces in the path.ReferencesThe mount unit file name must be named after the mount point directory, with spaces replaced by \x20. See How to escape spaces in systemd unit files? and systemd.mount.The Where entry must use \x20 to escape spaces in the path. See systemd.mount and The workaround is to use /usr/bin/env followed by the path in quotes..

• Question 78:

  A cloud engineer needs to block the IP address 192.168.10.50 from accessing a Linux server. Which of the following commands will achieve this goal?

  A. iptables -F INPUT -j 192.168.10.50 -m DROP

  B. iptables -A INPUT -s 192.168.10.30 -j DROP

  C. iptables -i INPUT --ipv4 192.168.10.50 -z DROP

  D. iptables -j INPUT 192.168.10.50 -p DROP

  Correct Answer: B

  Explanation: 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.

• Question 79:

  Application code is stored in Git. Due to security concerns, the DevOps engineer does not want to keep a sensitive configuration file, app . conf, in the repository. Which of the following should the engineer do to prevent the file from being uploaded to the repository?

  A. Run git exclude app. conf.

  B. Run git stash app. conf.

  C. Add app . conf to . exclude.

  D. Add app . conf to . gitignore.

  Correct Answer: D

  This will prevent the file app.conf from being tracked by Git and uploaded to the repository. The .gitignore file is a special file that contains patterns of files and directories that Git should ignore. Any file that matches a pattern in the .gitignore

  file will not be staged, committed, or pushed to the remote repository. The .gitignore file should be placed in the root directory of the repository and committed along with the other files.

  The other options are incorrect because:

  A. Run git exclude app.conf

  This is not a valid Git command. There is no such thing as git exclude. The closest thing is git update-index --assume-unchanged, which tells Git to temporarily ignore changes to a file, but it does not prevent the file from being uploaded to the

  repository.

  B. Run git stash app.conf

  This will temporarily save the changes to the file app.conf in a stash, which is a hidden storage area for uncommitted changes. However, this does not prevent the file from being tracked by Git or uploaded to the repository. The file will still be

  part of the working tree and the index, and it will be restored when the stash is popped or applied.

  C. Add app.conf to .exclude

  This will have no effect, because Git does not recognize a file named .exclude. The only files that Git uses to ignore files are .gitignore, $GIT_DIR/info/exclude, and core.excludesFile.

  References:

  Git - gitignore Documentation

  .gitignore file - ignoring files in Git | Atlassian Git Tutorial Ignoring files - GitHub Docs

  [CompTIA Linux+ Certification Exam Objectives]

• Question 80:

  An administrator has source code and needs to rebuild a kernel module. Which of the following command sequences is most commonly used to rebuild this type of module?

  A. ./configure make make install

  B. wget gcc cp

  C. tar xvzf build cp

  D. build install configure

  Correct Answer: A

  Explanation: The best command sequence to rebuild a kernel module from source code is A. ./configure make make install. This is the standard way to compile and install a Linux kernel module, as explained in the web search result 5. The other commands are either not relevant, not valid, or not sufficient for this task. For example:

  B. wget gcc cp will try to download, compile, and copy a file, but it does not specify the source code, the module name, or the destination directory. C. tar xvzf build cp will try to extract, build, and copy a compressed file, but it does not specify the file name, the module name, or the destination directory. D. build install configure will try to run three commands that are not defined or recognized by the Linux shell.