XK0-006 Troubleshooting Practice Test 5 — 15 Questions

Question 1

A Linux system experiences intermittent network connectivity. The administrator suspects a faulty network cable or switch port. Which TWO of the following commands can provide information about link status, errors, and packet drops on the interface? (Choose TWO.)

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

ip link show eth0. ip link show displays link status and error counters; ethtool can show detailed link and error statistics.

Answer

ss -i

Answer

ip addr show eth0

Answer

tcpdump -i eth0

Question 2

A Linux administrator wants to view all listening TCP ports and the associated processes on a system. Which command should be used?

Accepted Answer

ss -tlnp. The `ss -tlnp` command is correct because it displays all TCP listening sockets (`-t` for TCP, `-l` for listening) with numeric addresses (`-n`) and shows the associated process information (`-p`). This is the modern replacement for `netstat` and is the recommended tool on current Linux distributions for socket statistics.

Answer

lsof -i TCP

Answer

netstat -tulpn

Answer

nmap -sT localhost

Question 3

A technician needs to check the DNS A record for example.com using a specific DNS server at 8.8.8.8. Which command accomplishes this?

Accepted Answer

dig example.com @8.8.8.8 A. dig @8.8.8.8 example.com A queries the specified DNS server for the A record.

Answer

host -a example.com 8.8.8.8

Answer

dig -x 8.8.8.8 example.com

Answer

nslookup example.com 8.8.8.8

Question 4

A system administrator notices that the server is performing poorly. Running 'vmstat 1 5' shows high 'wa' values. Which subsystem is most likely experiencing a bottleneck?

Accepted Answer

Disk I/O. wa stands for I/O wait time, indicating the CPU is waiting for disk I/O. High wa suggests a disk bottleneck.

Answer

Memory

Answer

Network

Answer

CPU

Question 5

After modifying the network configuration on a RHEL 8 system using NetworkManager, what command should be used to apply the changes without restarting the network service?

Accepted Answer

nmcli con up 'System eth0'. nmcli con up <connection> activates the connection with new settings. nmcli connection reload reloads from disk but does not apply to active connections.

Answer

nmcli connection reload

Answer

ifup eth0

Answer

systemctl restart NetworkManager

Question 6

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

Accepted Answer

Corrupted initramfs. This error indicates the kernel cannot find the root filesystem, often due to a missing driver or incorrect root= parameter in the boot configuration.

Answer

Incorrect /etc/fstab entry

Answer

Full disk on /boot

Answer

Misconfigured GRUB timeout

Question 7

An administrator is troubleshooting a service that fails to start. They want to trace the system calls made by the service binary. Which command should they use?

Accepted Answer

strace. strace traces system calls and signals. It is used to debug what a program is doing at the kernel level.

Answer

ltrace

Answer

dmesg

Answer

lsof

Question 8

A web server is not responding on port 443. Using tcpdump to capture traffic on the server, which filter would capture only HTTPS packets?

Accepted Answer

tcpdump -i any tcp port 443. Port 443 is HTTPS. The filter 'port 443' captures traffic on that port.

Answer

tcpdump -i any port https

Answer

tcpdump -i any host 443

Answer

tcpdump -i any udp port 443

Question 9

Which command displays the current routing table on a Linux system?

Accepted Answer

ip route. ip route shows the routing table. The older route command is deprecated.

Answer

ip neigh

Answer

ip addr

Answer

ip link

Question 10

A user reports that they cannot reach a website by name, but they can reach it by IP address. Which file should be checked first for possible misconfiguration?

Accepted Answer

/etc/resolv.conf. The /etc/resolv.conf file contains DNS resolver settings. If it is incorrect, name resolution will fail.

Answer

/etc/nsswitch.conf

Answer

/etc/hosts

Answer

/etc/sysconfig/network

Question 11

During boot, the system drops into an emergency target. Which command can be used to repair the root filesystem from this environment?

Accepted Answer

fsck /dev/sda1. In emergency mode, the root filesystem is often mounted read-only. fsck can check and repair filesystems, but requires the filesystem to be unmounted.

Answer

mount -o remount,rw / && fsck /

Answer

xfs_repair /dev/sda1

Answer

journalctl -xb

Question 12

An administrator wants to monitor disk I/O performance in real-time, focusing on metrics like wait time and I/O queue size. Which tool is best suited for this?

Accepted Answer

iostat -x 1. iostat provides detailed disk I/O statistics including await, svctime, %util, and queue size.

Answer

vmstat

Answer

sar -b

Answer

free -h

Question 13

A technician needs to check the kernel ring buffer for hardware errors detected during system boot. Which command should be used?

Accepted Answer

dmesg. dmesg displays kernel ring buffer messages, which include hardware detection and errors.

Answer

journalctl -k

Answer

lspci

Answer

cat /var/log/boot.log

Question 14

A Linux server is experiencing high CPU usage. Which TWO commands can be used to identify which processes are consuming the most CPU? (Choose two.)

Accepted Answer

ps aux --sort=-%cpu. top and ps are standard process monitoring tools that show CPU usage.

Answer

iostat

Answer

vmstat

Answer

free

Question 15

A technician wants to capture network traffic to analyze a web server issue. Using tcpdump, which THREE options are useful for writing the capture to a file and avoiding name resolution? (Choose three.)

Accepted Answer

-n. -w writes to file, -n avoids name resolution, and -i specifies interface.

Answer

-c 100

Answer

-v