XK0-006 Troubleshooting Practice Test 2 — 15 Questions

Question 1

A Linux administrator is troubleshooting a DNS resolution issue. The system uses /etc/resolv.conf. Which two of the following directives are commonly found in this file? (Choose two.)

Accepted Answer

nameserver 8.8.8.8. /etc/resolv.conf typically contains nameserver entries and optionally search and domain directives.

Answer

domain localdomain

Answer

options timeout:2

Answer

hosts: files dns

Question 2

A system fails to boot with a kernel panic. The administrator suspects a corrupt initramfs or missing kernel module. Which three methods could be used to recover the system? (Choose three.)

Accepted Answer

Boot from a live CD/DVD, mount the root filesystem, and chroot. At the GRUB menu, editing boot parameters to add 'rd.break' drops into an emergency shell; adding 'single' boots into single-user mode; booting from a live CD allows chroot and repair.

Answer

Run 'fsck /dev/sda1' from the GRUB command line

Answer

Use 'systemctl rescue' from the boot prompt

Question 3

An administrator needs to identify which processes are consuming the most CPU and memory resources. Which two commands can provide this information? (Choose two.)

Accepted Answer

top. The `top` command provides a real-time, dynamic view of running processes, displaying CPU and memory usage by default and allowing sorting by resource consumption. The `ps aux --sort=-%mem` command lists all processes with detailed memory and CPU statistics, sorted by memory usage in descending order, making it easy to identify the most resource-intensive processes.

Answer

free -h

Answer

iostat -x

Answer

vmstat 1 5

Question 4

A Linux administrator needs to view all current IPv4 addresses assigned to network interfaces on a system. Which command should be used?

Accepted Answer

ip addr. The 'ip addr' command displays all IP addresses assigned to network interfaces. 'ifconfig' is deprecated, 'ip link' shows link-layer info, and 'hostname -I' only shows primary IPs.

Answer

ip link show

Answer

ifconfig -a

Answer

hostname -I

Question 5

A user reports that they cannot access a web server at 192.168.1.100. The administrator wants to check if the server is reachable and measure round-trip time. Which command is most appropriate?

Accepted Answer

ping 192.168.1.100. The `ping` command sends ICMP Echo Request packets to the target host and waits for ICMP Echo Reply packets, which directly tests reachability and measures round-trip time (RTT). This is the most appropriate tool for the administrator's stated goal of checking if the server is reachable and measuring RTT.

Answer

nmap -sn 192.168.1.100

Answer

traceroute 192.168.1.100

Answer

ss -tlnp | grep 192.168.1.100

Question 6

An administrator is troubleshooting a DNS issue and needs to query the authoritative name servers for example.com. Which dig command should be used?

Accepted Answer

dig example.com NS. dig example.com NS queries the name servers (NS records). A asks for IPv4, MX for mail, and ANY is often blocked.

Answer

dig example.com MX

Answer

dig example.com A

Answer

dig example.com ANY

Question 7

A system administrator notices that a web server is running but users cannot connect to port 443. Which ss command will show if the server is listening on that port?

Accepted Answer

ss -tlnp. ss -tlnp shows listening TCP sockets with numeric ports and process info. -t for TCP, -l listening, -n numeric, -p process.

Answer

ss -s

Answer

ss -tuln

Answer

ss -tan

Question 8

An administrator needs to capture network traffic on interface eth0 to a file for later analysis. Which tcpdump command is correct?

Accepted Answer

tcpdump -w capture.pcap -i eth0. Both A and C are valid tcpdump commands. tcpdump accepts options in any order, so '-w capture.pcap -i eth0' (A) and '-i eth0 -w capture.pcap' (C) are functionally equivalent. Option B uses '-f' which is for filter expression, not output file. Option D is invalid because '-w' expects a filename, not an interface.

Answer

tcpdump -i eth0 -f capture.pcap

Answer

tcpdump -w eth0 capture.pcap

Question 9

A system is experiencing high disk I/O wait. Which command can provide disk I/O statistics such as requests per second and average wait time?

Accepted Answer

iostat -x 1. iostat reports disk I/O statistics including r/s, w/s, await, %util. vmstat shows memory and CPU stats, free shows memory, sar can show I/O but iostat is I/O-specific.

Answer

sar -u 1 5

Answer

free -h

Answer

vmstat 1 5

Question 10

After a kernel panic, the system fails to boot. The administrator suspects a missing kernel module. Which command line should be added to the GRUB boot parameters to access a rescue shell and investigate?

Accepted Answer

rd.break. Adding 'rd.break' breaks before pivot_root and drops to a shell for troubleshooting. 'single' boots to single-user mode but may not help if module is missing. 'emergency' is for systemd targets.

Answer

systemd.unit=emergency.target

Answer

single

Answer

nomodeset

Question 11

An administrator needs to check the kernel ring buffer for hardware error messages after a system crash. Which command should be used?

Accepted Answer

dmesg. dmesg shows kernel ring buffer messages including hardware errors. journalctl -k shows kernel messages from systemd journal, but dmesg is the direct command for the ring buffer.

Answer

journalctl -k

Answer

tail -f /var/log/messages

Answer

strace -e trace=open

Question 12

A technician suspects a process is leaking file descriptors. Which command can be used to list open files associated with a specific PID?

Accepted Answer

lsof -p PID. lsof -p PID lists open files for that process. strace traces system calls, ltrace library calls, and top shows resource usage.

Answer

top -p PID

Answer

strace -p PID

Answer

ltrace -p PID

Question 13

An administrator wants to test SMTP connectivity to a mail server without actually delivering an email. Which curl command is most appropriate?

Accepted Answer

curl -v smtp://mail.example.com:25. curl -v smtp://mail.example.com:25 connects to SMTP and shows handshake. -I sends HEAD, not SMTP. --resolve is for DNS override.

Answer

curl --resolve mail.example.com:25:10.0.0.1 smtp://mail.example.com

Answer

curl -o /dev/null smtp://mail.example.com

Answer

curl -I smtp://mail.example.com

Question 14

A server running RHEL 8 has intermittent network connectivity. The administrator wants to view the current DNS resolver configuration. Which file should be examined?

Accepted Answer

/etc/resolv.conf. /etc/resolv.conf contains nameserver entries. /etc/nsswitch.conf defines order, /etc/hosts for static mapping, and /etc/sysconfig/network-scripts/ifcfg-* for interface config.

Answer

/etc/sysconfig/network-scripts/ifcfg-eth0

Answer

/etc/nsswitch.conf

Answer

/etc/hosts

Question 15

A technician needs to trace the system calls made by a running process to debug a performance issue. Which tool should be used?

Accepted Answer

strace -p PID. `strace -p PID` intercepts and records system calls (kernel-level operations like file I/O, network, and process control) made by a running process, which is exactly what is needed to trace system calls for debugging performance issues. The `-p` flag attaches strace to an existing process by its PID, allowing real-time monitoring of kernel interactions.

Answer

gdb -p PID

Answer

lsof -p PID

Answer

ltrace -p PID