XK0-005 Timed Practice Test 4 — 10 Questions

Question 1

A systems administrator needs to restrict SSH access to a Linux server so that only users in the 'sshusers' group can log in. Which configuration change should be made in /etc/ssh/sshd_config?

Accepted Answer

Add 'AllowGroups sshusers'. Option C is correct because the 'AllowGroups' directive in /etc/ssh/sshd_config restricts SSH login to only users who are members of the specified group. By adding 'AllowGroups sshusers', only users in the 'sshusers' group will be permitted to authenticate via SSH, while all others are denied. This is the standard OpenSSH mechanism for group-based access control.

Answer

Add 'AllowUsers sshusers'

Answer

Add 'DenyGroups all'

Answer

Add 'PermitRootLogin no' and add users to sshusers

Question 2

An administrator needs to update the system time using an NTP server immediately without waiting for the next scheduled sync. Which command should be used?

Accepted Answer

ntpdate pool.ntp.org. The `ntpdate` command is used to immediately synchronize the system clock with an NTP server, bypassing the daemon-based scheduled sync. Option D runs `ntpdate pool.ntp.org`, which performs a one-time query and sets the time instantly, making it the correct choice for an immediate update.

Answer

timedatectl set-ntp true

Answer

systemctl start ntpd

Answer

ntpq -p

Question 3

A company requires that all systems be configured to log all authentication attempts, both successful and failed. Which configuration file and directive should be used to ensure all auth messages are logged to /var/log/secure?

Accepted Answer

In /etc/rsyslog.conf: authpriv.* /var/log/secure. In rsyslog, the `authpriv` facility covers authentication and authorization messages, including both successful and failed login attempts. The directive `authpriv.* /var/log/secure` directs all messages from this facility to `/var/log/secure`, which is the standard secure log file on RHEL/CentOS systems. This meets the requirement to log all authentication attempts.

Answer

In /etc/rsyslog.conf: *.info /var/log/secure

Answer

In /etc/rsyslog.conf: auth.* /var/log/secure

Answer

In /etc/rsyslog.conf: kern.* /var/log/secure

Question 4

A Linux system is experiencing kernel panics after a recent update. The administrator wants to boot into a previous kernel version to restore functionality. Which three steps are required to achieve this? (Select THREE).

Accepted Answer

After booting, edit /etc/default/grub and set GRUB_DEFAULT to the saved entry, then run update-grub. Option A is correct because after booting into a working kernel, editing /etc/default/grub to set GRUB_DEFAULT to 'saved' and running update-grub (or grub-mkconfig) ensures that the GRUB bootloader will remember and default to the last successfully booted kernel, which can be the previous version. This step is necessary to make the temporary fix persistent across reboots.

Answer

Run 'yum reinstall kernel' to revert to the previous version

Answer

Edit /etc/fstab to change root filesystem parameters

Question 5

Based on the exhibit, what is the most likely cause of the sshd service failure?

Accepted Answer

Another process is already listening on port 22. The sshd service failed because another process is already listening on port 22, which prevents sshd from binding to that port. This is indicated by the error message in the exhibit (e.g., 'bind: Address already in use'), which is a common symptom when a conflicting service or a previously running instance of sshd occupies the port. The system cannot start a new instance of sshd until the port is freed.

Answer

The firewall is blocking port 22

Answer

The sshd configuration file has incorrect permissions

Answer

The sshd service is not installed

Question 6

A system administrator notices that a server's disk space is critically low. Which command should be used to identify the largest files or directories consuming space?

Accepted Answer

du -sh /*. Option D is correct because `du -sh /*` recursively calculates disk usage for each top-level directory and file under root, summarizing sizes in human-readable format. This directly identifies the largest space consumers, which is the stated goal. The `-s` flag provides a total per argument, and `/*` targets all immediate children of `/`.

Answer

ls -la /

Answer

fdisk -l

Answer

df -h

Question 7

A technician needs to find out which port the SSH daemon is listening on. Which command will show this information?

Accepted Answer

ss -tlnp. The `ss -tlnp` command displays listening TCP sockets with numeric addresses and the associated process information. The `-t` flag filters for TCP, `-l` shows only listening sockets, `-n` prevents DNS resolution, and `-p` reveals the PID and program name. Since SSH daemon (sshd) listens on TCP port 22 by default, this command will show the listening port and the sshd process.

Answer

lsof -i :22

Answer

nmap -p 22 localhost

Answer

netstat -i

Question 8

An administrator needs to ensure that a custom script /usr/local/bin/backup.sh runs every day at 2:00 AM and logs output to /var/log/backup.log. How should this be configured using systemd?

Accepted Answer

Create a systemd timer unit that activates a service unit, with OnCalendar=daily and the desired time.. Option C is correct because systemd timer units are the modern, recommended method for scheduling recurring tasks on Linux systems that use systemd. By creating a timer unit with `OnCalendar=daily` and specifying the desired time (e.g., `02:00:00`), the associated service unit will execute `/usr/local/bin/backup.sh` at 2:00 AM daily. The service unit can also redirect output to `/var/log/backup.log` using standard output/error directives, ensuring logging is handled natively within the systemd framework.

Answer

Use anacron with a delay of 0 and a period of 1 day.

Answer

Add a cron job with '0 2 * * * /usr/local/bin/backup.sh >> /var/log/backup.log 2>&1'.

Answer

Place the script in /etc/cron.daily/ and set the time with the 'START_HOURS_RANGE' variable.

Question 9

Based on the exhibit, the myapp service fails to start. Which troubleshooting step should be taken first?

Accepted Answer

Check that the application's configuration file exists and is readable. The exhibit shows a systemd unit file for the myapp service with `ExecStart=/usr/local/bin/myapp` and `Restart=on-failure`. The service fails to start, and the most common cause for such a failure is a missing or misconfigured application configuration file that the binary expects at launch. Option D is correct because verifying the configuration file's existence and readability is a fundamental prerequisite before investigating deeper issues like permissions or logs.

Answer

Increase the RestartSec value to allow more time for startup

Answer

Verify that /usr/local/bin/myapp has execute permission

Answer

Inspect the system journal for more detailed error messages

Question 10

A developer needs to run a one-time script after the network is up on a systemd-based server. Which unit type should be used?

Accepted Answer

oneshot. The `oneshot` unit type is correct because it is designed for services that run a single task to completion and then exit, making it ideal for a one-time script that must execute after the network is up. In systemd, `oneshot` units can be configured with `RemainAfterExit=no` (the default) to indicate they do not need to stay running, and they support ordering dependencies like `After=network-online.target` to ensure the network is available before the script runs.

Answer

forking

Answer

exec

Answer

simple