CompTIA CompTIA Certifications XK0-005 Questions & Answers

• Question 171:

  A DevOps engineer is working on a local copy of a Git repository. The engineer would like to switch from the main branch to the staging branch but notices the staging branch does not exist. Which of the following Git commands should the engineer use to perform this task?

  A. git branch --m staging

  B. git commit --m staging

  C. git status --b staging

  D. git checkout --b staging

  Correct Answer: D

  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. References: Git - git-checkout Documentation Git Tutorial: Create a New Branch With Git Checkout Git Branching - Basic Branching and Merging

• Question 172:

  A DevOps engineer needs to allow incoming traffic to ports in the range of 4000 to 5000 on a Linux server. Which of the following commands will enforce this rule?

  A. iptables -f filter -I INPUT -p tcp --dport 4000:5000 -A ACCEPT

  B. iptables -t filter -A INPUT -p tcp --dport 4000:5000 -j ACCEPT

  C. iptables filter -A INPUT -p tcp --dport 4000:5000 -D ACCEPT

  D. iptables filter -S INPUT -p tcp --dport 4000:5000 -A ACCEPT

  Correct Answer: B

  Explanation: 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.

• Question 173:

  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

  Correct Answer: AD

  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 174:

  A database administrator requested the installation of a custom database on one of the servers. Which of the following should the Linux administrator configure so the requested packages can be installed?

  A. /etc/yum.conf

  B. /etc/ssh/sshd.conf

  C. /etc/yum.repos.d/db.repo

  D. /etc/resolv.conf

  Correct Answer: C

  Explanation: The Linux administrator should configure /etc/yum.repos.d/db.repo so that the requested packages can be installed. This file defines a custom repository for yum, which is a package manager for RPM-based systems. The file should contain information such as the name, baseurl, gpgcheck, and enabled options for the repository. By creating this file and enabling the repository, the administrator can use yum to install packages from the custom repository. The /etc/ yum.conf file is the main configuration file for yum, but it does not define repositories. The /etc/ssh/sshd.conf file is the configuration file for sshd, which is a daemon that provides secure shell access to remote systems. The /etc/resolv.conf file is the configuration file for DNS resolution, which maps domain names to IP addresses. References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 19: Managing Packages and Software, page 559.

• Question 175:

  A Linux administrator has been tasked with installing the most recent versions of packages on a RPM-based OS. Which of the following commands will accomplish this task?

  A. apt-get upgrade

  B. rpm -a

  C. yum updateinfo

  D. dnf update

  E. yum check-update

  Correct Answer: D

  Explanation: 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.

• Question 176:

  A senior Linux administrator has created several scripts that will be used to install common system applications. These scripts are published to a reposito-ry to share with the systems team. A junior Linux administrator needs to re-trieve the scripts and make them available on a local workstation. Which of the following Git commands should the junior Linux administrator use to accom-plish this task?

  A. fetch

  B. checkout

  C. clone

  D. branch

  Correct Answer: C

  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]

• Question 177:

  An administrator created an initial Git repository and uploaded the first files. The administrator sees the following when listing the repository:

  

  The administrator notices the file . DS STORE should not be included and deletes it from the online repository. Which of the following should the administrator run from the root of the local repository before the next commit to ensure the file is not uploaded again in future commits?

  A. rm -f .DS STORE andand git push

  B. git fetch andand git checkout .DS STORE

  C. rm -f .DS STORE andand git rebase origin main

  D. echo .DS STORE >> .gitignore

  Correct Answer: D

  The correct answer is D. The administrator should run "echo .DS STORE >> .gitignore" from the root of the local repository before the next commit to ensure the file is not uploaded again in future commits.

  This command will append the file name .DS STORE to the end of the .gitignore file, which is a special file that tells Git to ignore certain files or directories that should not be tracked or uploaded to the repository. By adding .DS STORE to the

  .gitignore file, the administrator will prevent Git from staging, committing, or pushing this file in the future.

  The other options are incorrect because:

  A. rm -f .DS STORE andand git push

  This command will delete the file .DS STORE from the local repository and then push the changes to the remote repository. However, this does not prevent the file from being uploaded again in future commits, if it is recreated or copied to the

  local repository.

  B. git fetch andand git checkout .DS STORE

  This command will fetch the latest changes from the remote repository and then restore the file .DS STORE from the remote repository to the local repository. This is not what the administrator wants to do, as this will undo the deletion of the

  file from the online repository.

  C. rm -f .DS STORE andand git rebase origin main

  This command will delete the file .DS STORE from the local repository and then rebase the local branch onto the main branch of the remote repository. This will rewrite the commit history of the local branch and may cause conflicts or errors.

  This is not what the administrator wants to do, as this is a risky and unnecessary operation.

• Question 178:

  An administrator added the port 2222 for the SSH server on myhost and restarted the SSH server. The administrator noticed issues during the startup of the service. Given the following outputs: Which of the following commands will fix the issue?

  

  A. semanage port -a -t ssh_port_t -p tcp 2222

  B. chcon system_u:object_r:ssh_home_t /etc/ssh/*

  C. iptables -A INPUT -p tcp -- dport 2222 -j ACCEPT

  D. firewall-cmd -- zone=public -- add-port=2222/tcp

  Correct Answer: A

  The correct answer is A. semanage port -a -t ssh_port_t -p tcp 2222 This command will allow the SSH server to bind to port 2222 by adding it to the SELinux policy. The semanage command is a utility for managing SELinux policies. The port

  subcommand is used to manage network port definitions. The -a option is used to add a new record, the -t option is used to specify the SELinux type, the -p option is used to specify the protocol, and the tcp 2222 argument is used to specify

  the port number. The ssh_port_t type is the default type for SSH ports in SELinux.

  The other options are incorrect because:

  B. chcon system_u:object_r:ssh_home_t /etc/ssh/*

  This command will change the SELinux context of all files under /etc/ssh/ to system_u:object_r:ssh_home_t, which is not correct. The ssh_home_t type is used for user home directories that are accessed by SSH, not for SSH configuration

  files. The correct type for SSH configuration files is sshd_config_t. C. iptables -A INPUT -p tcp --dport 2222 -j ACCEPT This command will add a rule to the iptables firewall to accept incoming TCP connections on port 2222. However, this is

  not enough to fix the issue, as SELinux will still block the SSH server from binding to that port. Moreover, iptables may not be the default firewall service on some Linux distributions, such as Fedora or CentOS, which use firewalld instead.

  D. firewall-cmd --zone=public --add-port=2222/tcp

  This command will add a rule to the firewalld firewall to allow incoming TCP connections on port 2222 in the public zone. However, this is not enough to fix the issue, as SELinux will still block the SSH server from binding to that port.

  Moreover, firewalld may not be installed or enabled on some Linux distributions, such as Ubuntu or Debian, which use iptables instead.

  References:

  How to configure SSH to use a non-standard port with SELinux set to enforcing Change SSH Port on CentOS/RHEL/Fedora With SELinux Enforcing How to change SSH port when SELinux policy is enabled

• Question 179:

  A Linux system is failing to start due to issues with several critical system processes. Which of the following options can be used to boot the system into the single user mode? (Choose two.)

  A. Execute the following command from the GRUB rescue shell: mount -o remount, ro/sysroot.

  B. Interrupt the boot process in the GRUB menu and add systemd.unit=single in the kernel line.

  C. Interrupt the boot process in the GRUB menu and add systemd.unit=rescue.target in the kernel line.

  D. Interrupt the boot process in the GRUB menu and add single=user in the kernel line.

  E. Interrupt the boot process in the GRUB menu and add init=/bin/bash in the kernel line.

  F. Interrupt the boot process in the GRUB menu and add systemd.unit=single.target in the kernel line.

  Correct Answer: CF

  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.

• Question 180:

  A Linux system is failing to boot. The following error is displayed in the serial console:

  [[1;33mDEPEND[Om] Dependency failed for /data.

  [[1;33mDEPEND[Om] Dependency failed for Local File Systems

  ...

  Welcome to emergency mode! After logging in, type "journalctl -xb" to viewsystem logs, "systemct1 reboot" to reboot, "systemct1 default" to try again to boot into default mode.

  Give root password for maintenance

  (or type Control-D to continue}

  Which of the following files will need to be modified for this server to be able to boot again?

  A. /etc/mtab

  B. /dev/sda

  C. /etc/fstab

  D. /ete/grub.conf

  Correct Answer: C

  Explanation: The file that will need to be modified for the server to be able to boot again is /etc/fstab. The /etc/fstab file is a file that contains the information about the file systems that are mounted at boot time on Linux systems. The file specifies the device name, mount point, file system type, mount options, dump frequency, and pass number for each file system. The error message indicates that the dependency failed for /data, which is a mount point for a file system. This means that the system could not mount the /data file system at boot time, which caused the system to enter the emergency mode. The emergency mode is a mode that allows the administrator to log in as the root user and perform basic tasks such as repairing the system. The administrator should modify the /etc/fstab file and check the entry for the /data file system. The administrator should look for any errors or inconsistencies in the device name, file system type, or mount options, and correct them. The administrator should also verify that the device and the file system are intact and functional by using commands such as blkid, fdisk, fsck, or mount. The administrator should then reboot the system and see if the issue is resolved. The file that will need to be modified for the server to be able to boot again is /etc/fstab. This is the correct answer to the question. The other options are incorrect because they are not related to the file systems that are mounted at boot time (/etc/mtab, /dev/sda, or /etc/grub.conf). References: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 10: Managing Storage, page 321.