XK0-006 Practice Test 23 — 15 Questions

Question 1

Drag and drop the steps to set up a cron job that runs a script daily in the correct order.

Accepted Answer

Write the script, then make it executable, then add a crontab entry with daily schedule, then verify with crontab -l. Setting up a cron job correctly involves first writing the script that will be executed, then making it executable with chmod +x, then adding a crontab entry using crontab -e with the correct time specification (e.g., '0 0 * * *' for daily at midnight), and finally verifying the job is listed with crontab -l. This order ensures the script is ready and permissions are set before cron attempts to run it, and verification confirms the entry is valid.

Answer

Write the script, then add a crontab entry with daily schedule, then make it executable, then verify with crontab -l

Answer

Make the script executable, then write the script, then add a crontab entry, then verify with crontab -l

Answer

Add a crontab entry with daily schedule, then write the script, then make it executable, then verify with crontab -l

Question 2

A Linux administrator is troubleshooting a server that intermittently becomes unresponsive. The administrator suspects a memory leak. Which command should be used to monitor memory usage over time and identify the consuming process?

Accepted Answer

top. The `top` command provides a real-time, dynamic view of system processes, including memory usage (RES, VIRT, %MEM) and can be sorted by memory consumption. It updates continuously, making it ideal for monitoring memory usage over time and identifying the specific process responsible for a suspected memory leak.

Answer

free -h

Answer

ss -tuln

Answer

df -h

Question 3

A Linux administrator wants to search for the pattern 'ERROR' in all files under /var/log, ignoring case, and display line numbers. Which THREE options should be used with the grep command? (Select THREE).

Accepted Answer

-i. Option B (-i) is correct because it makes grep perform a case-insensitive match, so 'ERROR', 'error', and 'Error' are all found as required. Option D (-n) is correct because it prefixes each matching line with its line number, satisfying the requirement to display line numbers. Option E (-r) is correct because it recursively searches all files under the /var/log directory tree, which is needed to cover 'all files under /var/log'. Option A (-c) is not appropriate because it only counts matching lines instead of displaying them, and Option C (-v) is wrong because it inverts the match to show non-matching lines rather than the 'ERROR' pattern.

Answer

-c

Answer

-v

Question 4

Which THREE are valid methods to view logs in a systemd-based system?

Accepted Answer

journalctl. Option B, journalctl, is correct because it is the native command-line utility for querying and displaying logs collected by the systemd journal, allowing filtering by time, unit, priority, and other fields. Option C, journalctl -u sshd, is correct because the -u (or --unit) flag restricts journal output to messages belonging to the specified systemd unit, here the sshd service, which is a standard way to inspect a single service's logs. Option E, dmesg, is correct because it reads and prints the kernel ring buffer, exposing boot and kernel-level messages that are also relevant log data on a systemd-based host. Option A, cat /var/log/messages, is not a systemd-specific method and that file may not exist on many systemd distributions, since journald often stores logs in /var/log/journal or /run/log/journal rather than a plain messages file. Option D, systemctl status sshd, is not a log-viewing method per se; it shows unit state and only a short tail of recent journal entries as part of service status, so it does not qualify as a general method to view logs.

Answer

cat /var/log/messages

Answer

systemctl status sshd

Question 5

Refer to the exhibit. What is the total amount of RAM installed on the system?

Accepted Answer

7.7G. The output of `free -h` shows the total memory in the 'total' column of the 'Mem:' row, which is 7.7G. This value represents the total physical RAM installed and available to the system, as reported by the kernel from the hardware.

Answer

7.5G

Answer

8.0G

Answer

0.1G

Question 6

A user reports that a recently installed application fails to start. The application was installed via a shell script that added a repository and installed the package. The user runs 'ldd /usr/bin/app' and sees several 'not found' libraries. Which of the following is the MOST likely cause?

Accepted Answer

The installation script did not install all required dependencies.. The `ldd` command lists shared library dependencies for a binary. When it reports 'not found' libraries, it means the dynamic linker cannot locate the required `.so` files. Since the application was installed via a shell script that added a repository and installed the package, the most likely cause is that the script failed to install all required dependencies, leaving the binary unable to resolve its shared library links.

Answer

The kernel version is outdated.

Answer

SELinux is blocking the application.

Answer

The file system is corrupted.

Question 7

An administrator needs to harden SSH access. Which TWO settings in /etc/ssh/sshd_config are recommended to improve security? (Choose two.)

Accepted Answer

PermitRootLogin no. Option B (PermitRootLogin no) is correct because disabling direct root logins over SSH forces attackers to compromise a normal user account and then escalate privileges, removing a high-value, well-known target and enabling accountability through sudo or su. Option D (PasswordAuthentication no) is correct because it disables password-based authentication, requiring key-based (public/private key) authentication instead, which is not vulnerable to brute-force or credential-guessing attacks. Option A (PermitRootLogin yes) is wrong because it explicitly allows root to log in directly, the opposite of hardening. Option C (Protocol 1) is wrong because SSH protocol 1 is deprecated and insecure (weak integrity/crypto), and modern OpenSSH only supports protocol 2 anyway. Option E (Port 22) is wrong because it merely sets the default port and provides no real security benefit; changing the port is at most minor obscurity, not a recommended hardening control.

Answer

PermitRootLogin yes

Answer

Protocol 1

Answer

Port 22

Question 8

In the exhibit, what does 'Tasks: 11 (limit: 512)' indicate?

Accepted Answer

The cgroup pids controller is limiting the number of processes/threads.. The output shown is from the `systemd-cgls` command, which displays cgroup (control group) information. The line `Tasks: 11 (limit: 512)` indicates that the cgroup's pids controller is currently tracking 11 processes/threads within that cgroup and has a configured limit of 512. This limit restricts the total number of processes and threads that can be created in that cgroup, preventing fork bombs or resource exhaustion.

Answer

The process is using 512 MB of memory.

Answer

The service has been running for 512 seconds.

Answer

The number of threads is limited to 512.

Question 9

During boot, a Linux system displays a kernel panic indicating 'not syncing: VFS: Unable to mount root fs on unknown-block(0,0)'. Which of the following is the most likely cause?

Accepted Answer

Missing or corrupt initramfs. The error 'VFS: Unable to mount root fs on unknown-block(0,0)' indicates that the kernel cannot locate or access the root filesystem. This is most commonly caused by a missing or corrupt initramfs (initial RAM filesystem), which contains the necessary drivers and modules to mount the root filesystem. Without a valid initramfs, the kernel has no way to load storage drivers (e.g., for SATA, NVMe, or LVM) and thus fails to mount the root device.

Answer

Network configuration error

Answer

A failed filesystem check due to dirty file system

Answer

Incorrect GRUB timeout value

Question 10

A user needs to view the first 15 lines of a large log file. Which command is most appropriate?

Accepted Answer

head -n 15 filename. The command 'head -n 15 filename' is the most appropriate and efficient way to view the first 15 lines of a file. The head command is designed for this purpose, and the -n option specifies the number of lines. This is a standard Linux command and is more direct than piping cat to head.

Answer

cat filename | head -n 15

Answer

less -N 15 filename

Answer

tail -n 15 filename

Question 11

A Kubernetes administrator needs to expose a deployment named 'web-app' running on port 80 internally within the cluster. Which kubectl command creates a service of type ClusterIP that maps port 80 to the target port 8080 on the pods?

Accepted Answer

kubectl expose deployment web-app --port=80 --target-port=8080. The command 'kubectl expose deployment web-app --port=80 --target-port=8080' creates a Service of type ClusterIP (the default) that exposes the deployment 'web-app'. The --port flag sets the Service port to 80, and --target-port sets the container port to 8080, correctly mapping Service port 80 to pod port 8080.

Answer

kubectl create service nodeport web-app --tcp=80:8080

Answer

kubectl expose pod web-app --port=80 --target-port=8080

Answer

kubectl create service clusterip web-app --tcp=80:8080

Question 12

An administrator is configuring iptables on a server. The requirements are: allow incoming SSH (port 22) from the 192.168.1.0/24 network, drop all other incoming traffic, and allow all outgoing traffic. Which three iptables rules achieve this? (Choose THREE.)

Accepted Answer

iptables -A INPUT -p tcp --dport 22 -s 192.168.1.0/24 -j ACCEPT. Option A is correct because it appends an INPUT rule that matches TCP packets destined for port 22 (--dport 22) with source address 192.168.1.0/24 (-s 192.168.1.0/24) and accepts them, exactly fulfilling the requirement to allow SSH only from that subnet. Option B is correct because setting the OUTPUT chain's default policy to ACCEPT (iptables -P OUTPUT ACCEPT) permits all outgoing traffic, matching the stated requirement. Option E is correct because setting the INPUT chain's default policy to DROP (iptables -P INPUT DROP) ensures that any incoming traffic not explicitly accepted by the earlier SSH rule is dropped, satisfying the 'drop all other incoming traffic' requirement. Option C is not correct because FORWARD concerns traffic routed through the host, not traffic destined to the server itself, and the scenario does not require allowing forwarded packets. Option D is not correct because it accepts SSH from any source address, not restricted to 192.168.1.0/24 as required.

Answer

iptables -P FORWARD ACCEPT

Answer

iptables -A INPUT -p tcp --dport 22 -j ACCEPT

Question 13

A security administrator is reviewing SSH configuration. Which TWO settings enhance security by limiting authentication attempts and preventing password-based logins? (Choose two.)

Accepted Answer

MaxAuthTries 3. Option A, MaxAuthTries 3, is correct because this sshd_config directive limits the number of authentication attempts allowed per connection, so after three failed tries the server disconnects the client, directly reducing the risk of brute-force password guessing. Option B, PasswordAuthentication no, is correct because it disables password-based authentication entirely, forcing the use of stronger methods such as public key authentication and thereby preventing password logins. Option C, Protocol 2, is not correct here because although it enforces the more secure SSH-2 protocol, it does not limit authentication attempts or block password logins. Option D, PermitRootLogin no, is not correct because it only prevents direct root logins and does not restrict authentication attempts or password authentication for other users. Option E, Port 2222, is not correct because changing the listening port is only a minor obscurity measure and does not limit authentication attempts or prevent password-based logins.

Answer

Protocol 2

Answer

PermitRootLogin no

Answer

Port 2222

Question 14

A technician notices a script fails to execute because the user does not have permission. The script currently has permissions 644. The technician needs to add execute permission for the owner only. Which command accomplishes this?

Accepted Answer

chmod u+x script.sh. The script currently has permissions 644, meaning the owner has read/write (6), group has read (4), and others have read (4). The requirement is to add execute permission for the owner only. The command `chmod u+x script.sh` adds (+) execute (x) permission to the user (u) — the owner — without affecting group or others. This is the precise and minimal command to achieve the goal.

Answer

chmod a+x script.sh

Answer

chmod 755 script.sh

Answer

chmod 744 script.sh

Question 15

A Linux administrator needs to write a Bash script that runs a series of commands and stops immediately if any command fails. Which directive should be included at the beginning of the script?

Accepted Answer

set -e. The set -e directive (also written set -o errexit) instructs Bash to exit immediately if any command returns a non-zero exit status. Placing it at the top of a script ensures the script halts on the first failure rather than continuing with potentially harmful subsequent commands. This is the standard idiom for fail-fast Bash scripts.

Answer

#!/bin/bash

Answer

trap ... ERR

Answer

set -x