Free Practice Questions for CompTIA XK0-005 Exam

Step-by-Step Comprehensive Detailed Explanation:

Command Explanation:

The dig command queries DNS servers. If NXDOMAIN is received, the system cannot resolve the domain. The /etc/resolv.conf file contains the DNS server configuration.

Why Other Options are Incorrect:

B: /etc/hosts maps IP addresses to hostnames but is not queried unless configured in /etc/nsswitch.conf.

C: /etc/sysconfig/network-scripts contains network interface configurations, unrelated to DNS.

D: /etc/nsswitch.conf defines the order of name resolution methods, but it does not directly resolve domain names.

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.

The oom-killer was invoked because the system ran out of memory, and as a result, it killed the mysqld process to free memory. This is a clear indication that the server did not have enough physical memory to run the MariaDB service, leading to the process being terminated.

-s or --shell option in usermod is used to specify the new login shell for the user.

B is correct: usermod -s /bin/bash user sets /bin/bash as the user's shell.

Incorrect Options:

A: -g changes the user's primary group.

C: -p is for encrypted password string.

D: -d sets home directory.

The error indicates that the cron user does not have permission to run the cronjob. Creating a cron.allow file and adding the user cron to it will allow that user to run cronjobs. The cron.allow file is a security feature that controls which users are allowed to use cron.

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.

To create a symlink for /usr/local/bin/app-a, which was installed in /usr/local/share/app-a, the administrator can use the command ln -s /usr/local/share/app-a /usr/local/bin/app-a (A). This will create a symbolic link named /usr/local/bin/app-a that points to the original file /usr/local/share/app-a. The other commands will not create a symlink, but either move, copy, or synchronize the file. References:

[CompTIA Linux+ Study Guide], Chapter 3: Working with Files, Section: Creating Links

[How to Create Symbolic Links in Linux]

The git checkout -b staging command creates a new branch called staging and switches to it. This is useful when you want to create a new branch locally and begin working on it. The -b flag is used to create the branch if it doesn’t exist.

The output shows that the system is running low on available memory and has heavily utilized swap space (1824 MB out of 2047 MB). This indicates that both RAM and swap are being exhausted, which can lead to performance degradation. The system is likely experiencing memory pressure and may require additional RAM or optimizations to reduce memory consumption.

This command will create a local port forwarding, which means that connections from the SSH client are forwarded via the SSH server, then to a destination server. In this case, the destination server is the same as the SSH server (localhost), and the destination port is 80. The SSH client will listen on port 8080 on the local machine, and any connection to that port will be forwarded to port 80 on the server. This way, the administrator can securely access the web service running on port 80 on the server by using http://localhost:8080 on the local machine.

The other options are incorrect because:

B. ssh -R 8080:localhost:80 admin@server

This command will create a remote port forwarding, which means that connections from the SSH server are forwarded via the SSH client, then to a destination server. In this case, the destination server is the same as the SSH client (localhost), and the destination port is 80. The SSH server will listen on port 8080 on the remote machine, and any connection to that port will be forwarded to port 80 on the client. This is not what the administrator wants to do.

C. ssh -L 80:localhost:8080 admin@server

This command will also create a local port forwarding, but it will use port 80 on the local machine and port 8080 on the server. This is not what the administrator wants to do, and it may also fail if port 80 is already in use by another service on the local machine.

D. ssh -R admin@server

This command is incomplete and invalid. It does not specify any port numbers or destination addresses for the remote port forwarding. It will also fail if the SSH server does not allow remote port forwarding.