LFCS · topic practice

Troubleshooting practice questions

Practise Linux Foundation Certified System Administrator LFCS Troubleshooting practice questions — original exam-style scenarios with answer choices, explanations, and analysis of common mistakes.

Courseiva uses original exam-style practice questions designed for learning and revision. The goal is to understand the concepts, recognise exam patterns, and improve through explanations — not memorise copied exam dumps.

Reviewed byJohnson Ajibi· MSc IT Security
20 questionsDomain: Troubleshooting

What the exam tests

What to know about Troubleshooting

Troubleshooting questions test whether you can apply the concept in context, not just recognise a definition.

How the topic appears in realistic exam-style scenarios.

Which detail in the question changes the correct answer.

How to eliminate plausible but wrong options.

How to connect the question back to the wider exam objective.

Watch out for

Common Troubleshooting exam traps

  • Answering from memory before reading the full scenario.
  • Missing a constraint such as cost, availability, security, scope or command context.
  • Choosing a broad answer when the question asks for the most specific fix.
  • Ignoring why the wrong options are tempting.

Practice set

Troubleshooting questions

20 questions · select your answer, then reveal the explanation

Question 1mediummultiple choice
Read the full NAT/PAT explanation →

A system administrator is troubleshooting a user's report that a command 'myapp' is not found. The administrator checks the PATH variable and sees it includes /usr/local/bin. The administrator verifies that the binary 'myapp' exists in /usr/local/bin with permissions 755. However, running 'myapp' still fails with 'command not found'. What is the most likely cause?

An administrator is troubleshooting a server that runs a critical application. The server has 16 GB of RAM and 8 CPU cores. The administrator notices that the server becomes very slow during peak hours. Analysis of 'iostat -x 1' shows that the average wait time (await) for the main disk (sda) is consistently above 1000 ms, while the average service time (svctm) is around 5 ms. What is the most likely cause?

Which TWO commands can display the current environment variables?

A DevOps engineer wants to list all running processes sorted by memory usage in descending order. Which command should be used?

An administrator is troubleshooting intermittent connectivity issues. Running 'ping -c 100 -i 0.2 10.0.0.1' shows about 5% packet loss. What is the primary purpose of the '-i 0.2' option?

A storage administrator is troubleshooting a system where a new SCSI disk is detected by the kernel but not visible in /dev/disk/by-id/. What is the most likely cause?

Match each Linux networking command to its primary function.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Show/manipulate routing, devices, tunnels

Investigate sockets

Capture and analyze network traffic

Manage NetworkManager

Print network connections (legacy)

Question 8hardmultiple choice
Review the full routing breakdown →

A system administrator is troubleshooting network connectivity from a server that can reach internal resources but cannot access the internet. The server's /etc/sysconfig/network-scripts/ifcfg-eth0 file contains: BOOTPROTO=static, IPADDR=10.0.0.10, NETMASK=255.255.255.0, GATEWAY=10.0.0.1. The administrator runs 'ip route show' and sees: default via 10.0.0.1 dev eth0. However, 'ping 8.8.8.8' fails. Which is the most likely cause?

Which THREE are common tools used for network troubleshooting on Linux?

Question 10mediummultiple choice
Read the full Troubleshooting explanation →

A system administrator is troubleshooting a server that fails to mount an XFS filesystem on /dev/sdb1 during boot. The filesystem was recently created. Which command should the administrator run to check the filesystem for corruption?

A Linux administrator is troubleshooting a service that is running as the 'nobody' user but keeps failing because it cannot write to its log file. The log file is located at /var/log/app.log. Which TWO of the following methods will allow the service to write to the log file while maintaining security best practices?

Question 12mediummultiple choice
Read the full Troubleshooting explanation →

A systems administrator is troubleshooting a server that runs a database application. The server has 64 GB of RAM and 16 CPU cores. The administrator notices that the system is using a significant amount of swap space even though there is plenty of free memory. The 'free -m' command shows: total memory = 65536, used = 50000, free = 15536, buffers/cache = 10000, swap total = 8192, swap used = 6000. Which of the following is the most likely cause?

Question 13mediummultiple choice
Read the full Troubleshooting explanation →

Refer to the exhibit. The administrator receives alerts that the root filesystem is almost full. Which command could free up space by removing old log files?

Exhibit

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        50G   45G   5.4G  90% /
/dev/sdb1       100G   20G   80G   20% /data
Question 14mediummultiple choice
Read the full Troubleshooting explanation →

A system administrator is troubleshooting a performance issue. They need to identify which process is consuming the most CPU time over the last 24 hours. Which command should be used?

Question 15easymultiple choice
Read the full DHCP explanation →

A system administrator is troubleshooting a DHCP issue on a Linux client. After running 'dhclient -r eth0' and then 'dhclient eth0', the interface does not get an IP address. What command can be used to ensure the DHCP client process is fully released and restarted?

Question 16hardmultiple choice
Review the full routing breakdown →

A system administrator is troubleshooting network connectivity from a Linux server to a remote host at 10.0.0.1. The server has a default gateway of 192.168.1.1. Running `ping 10.0.0.1` fails, but `ping 192.168.1.1` succeeds. The output of `ip route show` shows a default route via 192.168.1.1. Which additional step should the administrator take to further investigate?

Question 17hardmulti select
Read the full DNS explanation →

An administrator is troubleshooting DNS resolution and wants to query the SOA record for a domain. Which three commands can be used? (Choose three.)

Question 18mediummultiple choice
Read the full Troubleshooting explanation →

A system administrator is troubleshooting a production web server running CentOS 7 that became unresponsive. The server is still pingable, but SSH connections timeout. The admin performs an out-of-band console login. The server appears frozen; typing commands shows no output. The admin is able to trigger a Magic SysRq key sequence (Alt+SysRq+f) to kill the hung processes. After that, the server resumes normal operation. However, the admin wants to understand the root cause. Upon checking 'dmesg', they see repeated messages: 'NMI watchdog: BUG: soft lockup - CPU#0 stuck for 22s!' followed by stack traces from a kernel thread. Which action should the admin take to prevent recurrence while maintaining system stability?

An administrator is troubleshooting a server that cannot mount an XFS filesystem on /dev/sdb1. The command mount /dev/sdb1 /data fails with 'wrong fs type, bad option, bad superblock'. Which three commands can help diagnose the issue? (Choose three.)

Question 20mediummultiple choice
Read the full DNS explanation →

A Linux system administrator is troubleshooting a DNS resolution issue on a Ubuntu 20.04 server. The server is configured with a static IP address on interface eth0 via /etc/netplan/01-netcfg.yaml. The administrator set the DNS servers to 8.8.8.8 and 8.8.4.4 in the cloud-config file. After applying the netplan configuration, the server can resolve hostnames correctly. However, after a few days, users report that the server can no longer resolve external hostnames. The administrator checks /etc/resolv.conf and sees that it contains only a local DNS server (127.0.0.53) and no references to the public DNS servers. The administrator wants to ensure that the public DNS servers are always used and that local DNS is bypassed. What is the best course of action?

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Frequently asked questions

What does the LFCS exam test about Troubleshooting?
Troubleshooting questions test whether you can apply the concept in context, not just recognise a definition.
How should I use these practice questions?
Select your answer before revealing the explanation. Then read why each option is right or wrong — this active recall approach builds retention far faster than re-reading notes.
Can I practise just Troubleshooting questions in a focused session?
Yes — the session launcher on this page draws every question from the Troubleshooting domain. Use a 10-question session first to gauge your baseline, then move to 20 or 30 once the weak spots are clear.
Where can I practise other LFCS topics?
Use the topic links above to move to related areas, or go back to the LFCS question bank to see all topics.
Are these real exam questions or dumps?
These are original practice questions written to test the same concepts the LFCS exam covers. They are not copied from any real exam or dump site.