XK0-005 Troubleshooting Practice Test 5 — 15 Questions

Question 1

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 2

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

Question 3

A user cannot start the Apache web service. The command 'systemctl start httpd' returns 'Failed to start httpd.service: Unit not found.' What is the most likely cause?

Accepted Answer

The httpd package is not installed. The error 'Failed to start httpd.service: Unit not found' indicates that systemd cannot locate a service unit file for httpd. This most commonly occurs when the httpd package (Apache HTTP Server) is not installed on the system. Without the package, no service unit file exists under /usr/lib/systemd/system/, so systemctl cannot start the service.

Answer

Network configuration is incorrect

Answer

Incorrect file permissions on /etc/httpd/

Answer

Disk space is full

Question 4

A system administrator notices that the root filesystem is at 95% capacity. Which command should be used to identify the directories consuming the most space?

Accepted Answer

du -sh /*. B is correct because `du -sh /*` calculates disk usage for each top-level directory under root, showing human-readable sizes. This directly identifies which directories consume the most space, allowing the administrator to pinpoint the source of the 95% capacity issue.

Answer

df -h

Answer

fdisk -l

Answer

ls -la /

Question 5

A Linux server experiences a kernel panic during boot. You need to capture the panic message for analysis. Which kernel parameter should be added to the GRUB command line to ensure the panic message is displayed before the system halts?

Accepted Answer

panic=10. The `panic=<seconds>` kernel parameter instructs the kernel to wait the specified number of seconds after a kernel panic before automatically rebooting. By setting `panic=10`, the system pauses for 10 seconds, allowing the panic message to remain on the console for capture and analysis before the system halts or reboots. This is the correct parameter to ensure the panic output is visible.

Answer

nomodeset

Answer

quiet

Answer

single

Question 6

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 7

A cron job that runs a backup script at 2 AM has not been executing. The syslog shows no errors from cron. What is the most likely reason the job is not running?

Accepted Answer

The cron daemon (crond) is not running. The most likely reason is that the cron daemon (crond) is not running. Cron jobs are executed by the cron daemon, which must be active in the background to read the crontab files and launch scheduled tasks. If crond is stopped or not started, no cron jobs will run, and syslog may not show cron-related errors because the daemon is not logging activity.

Answer

The system time zone is incorrect

Answer

The filesystem is full

Answer

The script has incorrect permissions

Question 8

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 9

Which TWO commands can be used to display the current kernel version on a Linux system?

Accepted Answer

uname -r. The `uname -r` command displays the kernel release version, which is the standard way to quickly check the current kernel version. The `cat /proc/version` command reads the /proc/version file, which contains a string that includes the kernel version, compiler information, and build date, making it another reliable method to view the kernel version.

Answer

modinfo

Answer

lsmod

Answer

dmesg

Question 10

Which TWO of the following are common causes of a system failing to boot? (Select two.)

Accepted Answer

A corrupted kernel image. A corrupted kernel image prevents the bootloader from loading the kernel into memory, causing the boot process to fail at the stage where the kernel is executed. Without a valid kernel, the system cannot initialize hardware or start the init process, resulting in a kernel panic or a hang.

Answer

A full hard drive

Answer

An incorrect system time zone

Answer

An incorrect IP address in /etc/network/interfaces

Question 11

Which THREE steps should be taken when diagnosing a network connectivity issue where a host cannot reach the internet but can ping the local gateway? (Select three.)

Accepted Answer

Examine the routing table with route -n. Option A is correct because the `route -n` command displays the kernel routing table without resolving hostnames, allowing you to verify whether a default gateway route (0.0.0.0/0) exists. If the host can ping the local gateway but not the internet, a missing or incorrect default route is a common cause, as traffic to external networks would have no path to forward.

Answer

Check ARP cache for the gateway

Answer

Run traceroute to a known external IP

Question 12

Refer to the exhibit. An administrator is troubleshooting an issue where services cannot write log files. Based on the output, which filesystem is most likely the cause?

Accepted Answer

/dev/sda1 (/). The output shows that the root filesystem /dev/sda1 mounted on / is at 100% usage. Since log files are typically written under /var/log, which resides on the root partition unless /var is a separate mount point, a full root filesystem prevents services from writing log files. The correct answer is D because the root filesystem is full, causing the write failures.

Answer

/dev/sda3 (/home)

Answer

Swap partition

Answer

/dev/sda2 (/var)

Question 13

Refer to the exhibit. A remote user is unable to SSH to the server. Based on the journalctl output, what is the most likely cause?

Accepted Answer

The user is entering the wrong password. The journalctl output shows 'Failed password for user' followed by 'Connection closed by authenticating user', which indicates that the SSH authentication process was attempted but failed due to an incorrect password. This log entry is generated by the SSH daemon (sshd) when a password authentication attempt fails, and the connection is subsequently closed. No other errors (e.g., connection refused, timeout, or denied by hosts.deny) are present, making incorrect password the most likely cause.

Answer

The SSH service is not running

Answer

The user's IP address is in the hosts.deny file

Answer

The SSH port is blocked by a firewall

Question 14

Refer to the exhibit. A user wants to execute the script 'script.sh' but receives a 'Permission denied' error. Which action should be taken to allow execution?

Accepted Answer

Add execute permission with chmod +x script.sh. The 'Permission denied' error indicates the script lacks the execute permission for the user. The `chmod +x script.sh` command adds the execute permission bit to the file's mode, allowing the user to run it as a program. This is the direct and correct fix for the issue.

Answer

Change the owner to the user with chown

Answer

Change the group to the user's primary group

Answer

Set the permissions to 644 with chmod

Question 15

A company uses a Linux server running a web application. Users report that they cannot access the website. The administrator checks the web server status and finds it is not running. Which command should the administrator use to view the reason for the service failure?

Accepted Answer

journalctl -xe. The `journalctl -xe` command displays the systemd journal log with the `-x` flag adding explanatory context and `-e` jumping to the end of the log, which is the most direct way to view the reason a systemd-managed service like httpd failed. Since the web server is managed by systemd, its failure reason (e.g., exit code, segfault, configuration error) is recorded in the journal, and this command retrieves that specific failure detail without requiring manual log file parsing.

Answer

systemctl status httpd --full

Answer

tail -f /var/log/httpd/access_log

Answer

dmesg | grep httpd