XK0-005 Practice Test 3 — 10 Questions

Question 1

A database server running on Linux is experiencing high load. The administrator runs 'strace -p <pid>' and sees many 'epoll_wait' and 'futex' calls. Which THREE of the following are possible causes of the high load? (Choose THREE.)

Accepted Answer

Disk I/O contention causing processes to wait.. Option A is correct because 'epoll_wait' indicates the process is waiting for I/O events, and 'futex' calls are used for synchronization. Disk I/O contention can cause the database process to block on these system calls, leading to high load as the kernel schedules other tasks while waiting for I/O to complete.

Answer

CPU frequency scaling is set to powersave.

Answer

A memory leak in the database process.

Question 2

A user reports that a Linux workstation fails to boot and displays 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)'. Which of the following is the most likely cause?

Accepted Answer

The root filesystem device is incorrectly specified in the kernel command line.. The error 'VFS: Unable to mount root fs on unknown-block(0,0)' indicates that the kernel cannot locate the root filesystem device. The most likely cause is that the root filesystem device is incorrectly specified in the kernel command line (e.g., via a bootloader parameter like root=), preventing the kernel from finding the correct block device to mount as root.

Answer

A filesystem listed in /etc/fstab has errors.

Answer

A memory module is faulty.

Answer

The boot loader is missing or corrupted.

Question 3

A user reports that the /data directory is inaccessible. The Linux administrator runs the commands shown in the exhibit. Which of the following is the most likely cause of the issue?

Accepted Answer

The filesystem is full and has become corrupted.. The 'Input/output error' when accessing /data, combined with the 'Structure needs cleaning' message from dmesg, indicates filesystem corruption on /dev/sdb1. This is a classic symptom of a full filesystem that has become corrupted, not a simple permission or mount issue. The administrator's inability to read or write to the directory, despite the mount appearing normal, points to underlying filesystem damage.

Answer

The user does not have read permissions on /data.

Answer

The device /dev/sdb1 is not present.

Answer

The filesystem is mounted as read-only.

Question 4

A developer is writing a Bash script that must be portable across different Linux distributions. The script needs to check if a package is installed. Which command should be used to achieve this portability?

Accepted Answer

command -v package. The `command -v package` command is the most portable way to check if a package is installed across different Linux distributions because it uses the POSIX-standard `command` shell built-in, which works in any Bourne-compatible shell (bash, sh, dash, etc.) regardless of the underlying package manager. It returns the path to the executable if the package's binary is in the PATH, or nothing if it is not installed, making it distribution-agnostic.

Answer

which package

Answer

dpkg -l package

Answer

rpm -q package

Question 5

A senior administrator is troubleshooting a shell script that fails to execute properly. The script starts with #!/bin/bash and has execute permissions. Which of the following could cause the script to fail to run when invoked as ./script.sh?

Accepted Answer

The script contains carriage return characters (\r).. Option B is correct because carriage return characters (\r) are a common issue when scripts are edited on Windows and then transferred to Linux. The shebang line #!/bin/bash expects a Unix-style line ending (LF), but \r characters cause the shell to interpret the command interpreter as '/bin/bash\r', which is not a valid executable path. This results in a 'No such file or directory' error when the script is invoked as ./script.sh, even though permissions are correct.

Answer

The shebang line is not on the first line.

Answer

The script uses #!/bin/sh instead of bash.

Answer

The script starts with a byte order mark (BOM).

Question 6

A Linux system is experiencing high CPU load. The administrator runs 'top' and sees that the 'kworker' processes are consuming significant CPU time. What is the most likely cause?

Accepted Answer

A hardware interrupt storm caused by a failing disk controller. The 'kworker' processes in the 'top' output indicate kernel workqueue threads that handle deferred work. High CPU usage by kworker is typically caused by a hardware interrupt storm, often from a failing disk controller or other faulty hardware generating excessive interrupts that the kernel must service. This forces the workqueue to constantly process interrupt-related tasks, consuming significant CPU time.

Answer

A kernel module memory leak

Answer

A user process stuck in an infinite loop

Answer

Insufficient memory causing swapping

Question 7

A Linux server runs a web application that frequently runs out of file descriptors. Which configuration change would permanently increase the maximum number of open files for all users?

Accepted Answer

Edit /etc/security/limits.conf and add 'soft nofile 65536' and 'hard nofile 65536'. Option D is correct because editing /etc/security/limits.conf with both 'soft nofile' and 'hard nofile' entries permanently raises the per-user limit on open file descriptors for all users (or specified users/groups) at login. The soft limit is the current working limit, while the hard limit is the maximum ceiling; setting both ensures the user can reach the desired value without needing to run ulimit with root privileges.

Answer

Set 'fs.file-max = 65536' in /etc/sysctl.conf

Answer

Add 'session required pam_limits.so' to /etc/pam.d/login

Answer

Run 'ulimit -n 65536' in a startup script

Question 8

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 9

A Linux engineer is troubleshooting a server that fails to boot. The server displays a message indicating 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)'. Which TWO actions should the engineer take to resolve this issue? (Choose TWO.)

Accepted Answer

Boot from a rescue disk and rebuild the initramfs with the necessary filesystem modules. The error 'Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)' indicates the kernel cannot locate or mount the root filesystem. Option B is correct because rebuilding the initramfs from a rescue disk ensures the necessary filesystem drivers (e.g., ext4, xfs) are included, which may have been missing or corrupted. Option D is correct because the root= parameter in the bootloader configuration (e.g., GRUB) tells the kernel which device/partition to mount as root; a typo or incorrect value (e.g., wrong UUID or device name) will cause this exact panic.

Answer

Reinstall GRUB to the Master Boot Record

Answer

Run fsck on the root partition to check for filesystem corruption

Answer

Disable SELinux by adding selinux=0 to the kernel command line

Question 10

A system administrator needs to check the current runlevel on a system that uses systemd. Which command should the administrator use?

Accepted Answer

systemctl get-default. Option C is correct because `systemctl get-default` displays the default target (runlevel equivalent) on a systemd-based Linux system. Systemd uses targets instead of traditional SysV runlevels, and this command shows which target is set as the default at boot, such as `multi-user.target` or `graphical.target`.

Answer

hostnamectl

Answer

getenforce

Answer

uname -r