XK0-005 Practice Test 17 — 15 Questions

Question 1

The administrator wants to block the IP address shown in the exhibit. Which command should be used?

Accepted Answer

iptables -A INPUT -s 192.168.1.100 -j DROP. Option C is correct because `iptables -A INPUT -s 192.168.1.100 -j DROP` appends a rule to the INPUT chain that drops all incoming packets from the source IP 192.168.1.100. This is the standard Linux firewall command for blocking traffic at the network layer using netfilter, and it works immediately without requiring a service restart.

Answer

fail2ban

Answer

echo '192.168.1.100' >> /etc/hosts.deny

Answer

firewall-cmd --add-source=192.168.1.100 --permanent

Question 2

A system administrator is troubleshooting a network issue where a server cannot reach external websites. The server can ping the default gateway and internal hosts. Which TWO commands should the administrator use to further diagnose the problem? (Choose TWO.)

Accepted Answer

nslookup google.com. The server can reach internal hosts and the default gateway, which rules out Layer 2/3 connectivity issues within the local network. However, it cannot reach external websites, suggesting a DNS resolution failure or a routing problem beyond the gateway. 'nslookup google.com' (A) tests DNS resolution by querying the configured DNS server for the IP address of google.com; if it fails, the issue is with DNS. 'traceroute 8.8.8.8' (E) traces the path to a known external IP (Google's public DNS), bypassing DNS, to determine if packets are being dropped or misrouted after the gateway.

Answer

route -n

Answer

ping 127.0.0.1

Answer

ifconfig eth0

Question 3

A user attempts to run a command using sudo but receives 'user is not in the sudoers file. This incident will be reported.' Which file should be edited to grant the user sudo access?

Accepted Answer

Use visudo to edit /etc/sudoers. The correct answer is D because the sudoers file, typically located at /etc/sudoers, controls which users and groups are permitted to run commands with sudo. The visudo command must be used to edit this file safely, as it performs syntax checking to prevent lockouts due to misconfiguration. Directly editing /etc/sudoers with a regular text editor can lead to syntax errors that break sudo functionality.

Answer

Edit /etc/passwd directly

Answer

Edit /etc/group to add user to the wheel group

Answer

Edit /etc/shadow

Question 4

A system administrator notices that a Linux server is running low on disk space. Which command should be used to identify which directories are consuming the most space?

Accepted Answer

du -h /path | sort -rh. Option D is correct because the `du -h /path | sort -rh` command recursively calculates disk usage for each directory under the specified path, displays sizes in human-readable format (`-h`), and then sorts the output in reverse numerical order (`-rh`), showing the largest directories first. This directly identifies which directories are consuming the most space, which is exactly what the system administrator needs.

Answer

ls -laR

Answer

find / -size +100M

Answer

df -h

Question 5

An application is being denied access to a file due to SELinux. Which command can be used to temporarily set the SELinux context of the file to match the expected type for the application?

Accepted Answer

chcon -t httpd_sys_content_t /var/www/html/index.html. Option A is correct because the `chcon` command is used to temporarily change the SELinux context of a file without modifying the SELinux policy. By specifying `-t httpd_sys_content_t`, the file's type is set to the expected type for Apache (httpd) to access it, resolving the denial immediately. This change is not persistent across file system relabeling, making it ideal for temporary troubleshooting.

Answer

setenforce 0

Answer

restorecon -v /var/www/html/index.html

Answer

semanage fcontext -a -t httpd_sys_content_t /var/www/html

Question 6

A network administrator needs to diagnose connectivity issues from a Linux server to a remote host. Which of the following tools can provide information about the path and latency? (Choose three.)

Accepted Answer

mtr. C (mtr) is correct because it combines the functionality of traceroute and ping into a single diagnostic tool, continuously probing each hop along the path to a remote host and reporting both the route and real-time latency statistics. This makes it ideal for identifying where packet loss or high latency occurs along the network path.

Answer

iproute

Answer

netstat

Question 7

A user reports that a service fails to start with the error 'Permission denied'. The service runs under a non-root user. Which command should the administrator use to check if the service has the correct file permissions?

Accepted Answer

namei -l /path/to/service. The error 'Permission denied' when starting a service under a non-root user often involves not just the file's own permissions but also the permissions of each directory in the path leading to the service binary. The `namei -l` command recursively lists the permissions of every component in the path, revealing if any parent directory lacks execute (search) permission for the service user, which would block access even if the binary itself is correctly set. This makes it the most comprehensive tool for diagnosing path-based permission issues.

Answer

ls -l /path/to/service

Answer

getfacl /path/to/service

Answer

stat /path/to/service

Question 8

A Linux system fails to boot and displays a kernel panic immediately after the GRUB menu. The administrator needs to boot into a rescue environment. Which GRUB boot parameter should the administrator add to the kernel line?

Accepted Answer

systemd.unit=rescue.target. Option C is correct because when a Linux system experiences a kernel panic immediately after GRUB, the administrator needs to boot into a minimal rescue environment that loads essential system services. The `systemd.unit=rescue.target` parameter tells systemd to start the rescue target, which mounts the root filesystem and starts only the most basic services, allowing the administrator to diagnose and repair the system. This is the proper GRUB kernel parameter for systemd-based distributions to enter a rescue shell without fully booting into the default multi-user or graphical target.

Answer

single

Answer

init=/bin/bash

Answer

quiet splash

Question 9

During peak hours, a web server experiences timeouts. The kernel log shows 'possible SYN flooding'. Which kernel parameter should be increased to mitigate this?

Accepted Answer

net.ipv4.tcp_max_syn_backlog. The kernel log message 'possible SYN flooding' indicates that the system's SYN backlog queue is full, causing new connection requests to be dropped. Increasing `net.ipv4.tcp_max_syn_backlog` expands the maximum number of SYN requests that can be queued before the kernel starts dropping them, directly mitigating the issue.

Answer

net.ipv4.tcp_syncookies

Answer

net.core.somaxconn

Answer

net.core.rmem_default

Question 10

After editing the network configuration file /etc/sysconfig/network-scripts/ifcfg-ens33 on a CentOS system, the network service fails to restart with an error message. Which command should be used to display detailed error messages from the network service?

Accepted Answer

systemctl status network. The `systemctl status network` command is the correct tool to display detailed error messages from the network service because it shows the current status, recent log entries, and any failure messages from the systemd unit managing the network service. On CentOS, network services are controlled by systemd, and `systemctl status` directly queries the unit's state and journal for errors, making it the most straightforward diagnostic command after a restart failure.

Answer

ip link

Answer

journalctl -u network

Answer

ifconfig

Question 11

A user runs a command and receives the error 'bash: myapp: command not found'. The administrator confirms the binary exists in /usr/local/bin. Which environment variable should be checked?

Accepted Answer

HOME. The PATH environment variable defines the directories the shell searches for executables when a command is typed. Even though the binary exists in /usr/local/bin, if that directory is not listed in PATH, the shell will not find it and will return 'command not found'. Checking and correcting PATH resolves this issue.

Answer

SHELL

Answer

LD_LIBRARY_PATH

Answer

PATH

Question 12

Given the journalctl output for the httpd service, which of the following is the most likely cause?

Accepted Answer

The /var/www directory is missing the execute (x) permission for the Apache user. The error explicitly states missing search permissions on a component of the path, which typically means a directory in the path lacks execute permission. The most common cause is the /var/www directory lacking execute permission for the Apache user.

Answer

The file /var/www/html/index.html has incorrect SELinux context

Answer

The Apache service is running under the wrong user

Answer

The file /var/www/html/index.html is missing read permission for the Apache user

Question 13

A Linux system fails to boot after a disk replacement. The administrator examines /etc/fstab and sees the above. What is the most likely result of this configuration?

Accepted Answer

The system will boot into an emergency shell. The /etc/fstab entry contains an incorrect UUID for the root filesystem. During boot, systemd reads fstab and attempts to mount the root partition using the specified UUID. When the UUID does not match any available block device, the mount fails, and because the root filesystem is critical, the system drops into an emergency shell to allow manual intervention.

Answer

The system will boot normally using the device name

Answer

The system will ignore the incorrect UUID and try next entry

Answer

The system will prompt for manual fsck

Question 14

Which TWO commands can be used to check disk space usage on a Linux system?

Accepted Answer

du. The `du` (disk usage) command estimates file and directory space usage, allowing you to check disk space consumed by specific paths. The `df` (disk free) command reports the total, used, and available space on mounted filesystems. Both are standard tools for inspecting disk space on Linux systems.

Answer

mount

Answer

lsof

Answer

fdisk

Question 15

A Linux server experiences a kernel panic after a recent driver update. The system is still operational but unstable. Which command should be used to gather detailed information about the kernel modules currently loaded?

Accepted Answer

lsmod. B is correct because `lsmod` lists all currently loaded kernel modules by reading the `/proc/modules` file, showing their size, usage count, and dependencies. In a kernel panic scenario after a driver update, this command quickly reveals which modules are active, helping identify the problematic driver without further destabilizing the system.

Answer

modinfo

Answer

dmesg

Answer

modprobe -l

XK0-005 Practice Test 17 — 15 Questions

Exhibit

XK0-005 Practice Test 17 — 15 Questions

Exhibit